WO2003088436A1 - Wavelength monitor device - Google Patents

Wavelength monitor device Download PDF

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Publication number
WO2003088436A1
WO2003088436A1 PCT/JP2002/003715 JP0203715W WO03088436A1 WO 2003088436 A1 WO2003088436 A1 WO 2003088436A1 JP 0203715 W JP0203715 W JP 0203715W WO 03088436 A1 WO03088436 A1 WO 03088436A1
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WO
WIPO (PCT)
Prior art keywords
wavelength
optical axis
fabry
light
perot resonator
Prior art date
Application number
PCT/JP2002/003715
Other languages
French (fr)
Japanese (ja)
Inventor
Yohei Mikami
Masao Imaki
Yoshihito Hirano
Original Assignee
Mitsubishi Denki Kabushiki Kaisha
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Denki Kabushiki Kaisha filed Critical Mitsubishi Denki Kabushiki Kaisha
Priority to PCT/JP2002/003715 priority Critical patent/WO2003088436A1/en
Priority to PCT/JP2002/009173 priority patent/WO2003087898A1/en
Publication of WO2003088436A1 publication Critical patent/WO2003088436A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/28—Interference filters
    • G02B5/284—Interference filters of etalon type comprising a resonant cavity other than a thin solid film, e.g. gas, air, solid plates
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
    • G01J2009/0257—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods multiple, e.g. Fabry Perot interferometer
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/001—Optical devices or arrangements for the control of light using movable or deformable optical elements based on interference in an adjustable optical cavity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
    • H01S5/0687—Stabilising the frequency of the laser

Definitions

  • the present invention relates to a wavelength monitoring device that monitors the wavelength of a laser beam used in a wavelength division multiplexing transmission (WDM) system or the like, and in particular, detects the laser beam that has passed through a Fabry-Perot resonator to reduce the oscillation wavelength of the laser beam. It relates to the wavelength monitoring device to be measured.
  • WDM wavelength division multiplexing transmission
  • FIG. 1 is a configuration diagram showing a conventional wavelength monitor device disclosed in Japanese Patent Application Laid-Open No. H03-160774.
  • a semiconductor laser 101 can control the wavelength of an emitted optical signal.
  • the light emitted from the semiconductor laser 101 is converted into parallel light by the optical lens 105, and the parallel light is further split into two directions by the beam splitter 106.
  • One of the branched lights is focused on a photodetector 108, for example, a photodiode via a lens 107.
  • the other light is incident on the Fabry-Bellows resonator.
  • the Fabry-Perot resonator 111 has reflection films 109 and 110 and is made of two kinds of optical materials.
  • the light transmitted through the Fabry-Perot resonator 111 is focused on the photodetector 113 via the lens 112.
  • FIG. 2 is a configuration diagram of the Fabry-Perot resonator 111 in FIG.
  • the temperature coefficient ⁇ of a Fabry-Perot resonator made of one type of optical material is expressed by equation (1).
  • ⁇ is the refractive index of the optical material
  • ⁇ is the linear expansion coefficient in the light ray direction.
  • the Fabry-Perot resonator length becomes Because the wavelength dependence of the light intensity emitted from the semiconductor laser 101 and transmitted through the Fabry-Perot resonator 111 does not change depending on the temperature, the wavelength is accurately monitored irrespective of the temperature of the resonator 111. Can be.
  • the Fabry-Perot resonator 111 is composed of two kinds of optical materials having different signs of the temperature coefficient ⁇ . In order to make the temperature coefficient of the entire Fabry-Perot resonator 111 zero, it is necessary to satisfy Expression (2).
  • n. 101 is the refractive index and physical length of the first optical material, respectively, and r x is the temperature coefficient of the first optical material according to the equation (1). Also n. 2, 1 02 the refractive index and physical length of the second optical material, respectively it, r 2 is Ru temperature coefficient der of the second optical material.
  • the present invention has been made in view of the above, and comprises a Fabry-Perot resonator whose resonator length does not change in response to a temperature change, using a uniaxial birefringent crystal of one material, thereby simplifying the configuration. It is an object of the present invention to obtain a wavelength monitor using a Fabry-Perot resonator that can realize mass production.
  • a wavelength monitor device for monitoring the wavelength of laser light output from a semiconductor laser
  • one axis of one material cut out so that an optical axis is inclined at a predetermined angle with respect to a plane perpendicular to the optical axis of the laser light.
  • a light reflecting film that reflects light on a surface on which the laser light enters and a surface on which the laser light exits, and outputs transmitted light having different transmission intensities according to the wavelength of the laser light.
  • the present invention it is possible to configure a Fabry-Perot resonator in which the resonator length does not change in response to a temperature change by using a uniaxial birefringent crystal of one material, so that the configuration is simplified, The reliability as a wavelength monitor is improved, and troublesome adjustment work is not required during production, and mass production can be realized.
  • the laser light output from the semiconductor laser is polarized in one direction
  • the uniaxial birefringent crystal constituting the Floupe Perot resonator is The optical axis is in a plane parallel to a plane formed by the optical axis and the polarization direction, and the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser beam.
  • the wavelength of the laser beam is aligned with the extraordinary optical axis, and a wavelength monitor having a Fabry-Perot resonator having a temperature compensation function can be realized using a uniaxial birefringent crystal of one material. .
  • the following invention is the above invention, wherein the laser output from the semiconductor laser is The light is polarized in one direction, and the uniaxial birefringent crystal constituting the Fabry-Perot resonator has an optical axis in a plane perpendicular to a plane formed by the optical axis and the polarization direction of the laser light.
  • the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser beam.
  • the present invention it is possible to realize a wavelength monitor having a Fabry-Perot resonator having a temperature compensation function by using a uniaxial birefringent crystal of one material in which the polarization of laser light is aligned with the ordinary optical axis.
  • the uniaxial birefringent crystal constituting the Fabry-Perot resonator is based on a refractive index of the uniaxial birefringent crystal, a linear expansion coefficient in an optical axis direction, and a thermo-optic coefficient. An angle of the axis with respect to the optical axis is set.
  • a uniaxial birefringent crystal in which the angle of the optical axis with respect to the optical axis is set based on the refractive index, the coefficient of linear expansion in the optical axis direction, and the thermo-optic coefficient is used.
  • a uniaxial birefringent crystal Using a uniaxial birefringent crystal, a highly reliable wavelength monitor with a Fabry-Perot resonator having a temperature compensation function can be realized.
  • the uniaxial birefringent crystal constituting the Fabry-Perot resonator has a line in the optical axis direction such as the refractive index of the uniaxial birefringent crystal.
  • the angle of the optical axis with respect to the optical axis is set so that the sum of the product of the expansion coefficient and the thermo-optic coefficient coincides with zero.
  • the optical axis when aligning the polarization of the laser light with the extraordinary optical axis, the optical axis is adjusted so that the sum of the product of the refractive index and the linear expansion coefficient in the optical axis direction and the thermo-optic coefficient becomes zero. Since a uniaxial birefringent crystal whose angle to the optical axis is set is used, it is possible to realize a wavelength monitor having a Fabry-Earth single resonator having a highly accurate temperature compensation function.
  • the uniaxial birefringent crystal constituting the Fabry-Perot resonator has a refractive index of the uniaxial birefringent crystal and a line extending in the optical axis direction.
  • the sum of the product of the expansion coefficient and the thermo-optic coefficient must be equal to zero.
  • the angle of the optical axis with respect to the optical axis is set.
  • the optical axis of the optical axis is adjusted so that the sum of the product of the refractive index and the linear expansion coefficient in the optical axis direction and the thermo-optic coefficient coincides with zero. Since a uniaxial birefringent crystal having an angle with respect to is used, it is possible to realize a wavelength monitor having a fabricator having a high-precision temperature compensation function.
  • the uniaxial birefringent crystal constituting the Fabry-Perot resonator is formed of ⁇ - ⁇ , ⁇ -BO, and L i I 0 3 .
  • the angle of the optical axis with respect to the optical axis is 4.35 degrees
  • the angle of the optical axis with respect to the optical axis is 6 4.75 degrees
  • the present invention aligns the polarization of the laser beam to the extraordinary optical axis, and as a uniaxial birefringent crystal, ⁇ - BBO, j3 _BBO, when using any of L i I 0 3 Te odor, high A wavelength monitor having a Fabry-Perot resonator with an accurate temperature compensation function can be realized.
  • a uniaxial birefringent crystal constituting the Fuaburipero resonator, ⁇ - ⁇ , ⁇ - ⁇ BO , L i ⁇ 0 3, and C a C0 3 either, alpha-case of BBO, and angle 76.9 5 degrees with respect to the optical axis of the optical axis, J8- for BBO, angle 5 7 against the optical axis of the optical axis .
  • the present invention aligns the polarization of the laser beam on the ordinary axis and as uniaxial birefringent crystal, alpha - used ⁇ , / 3- BBO, one of L i I 0 3, C a CO 3
  • a wavelength monitor having a Fabry-Perot resonator having a high-precision temperature compensation function can be realized.
  • the following invention is the above-mentioned invention, wherein one component constituting the Fabry-Perot resonator is Axial birefringent crystals can satisfy the temperature compensation condition and adjust the wavelength discrimination region by changing the thickness in the direction of the optical axis while maintaining the set angle of the optical axis with respect to the optical axis.
  • the temperature compensation condition does not depend on the thickness of the uniaxial birefringent crystal, it is possible to obtain a Fabry-Perot resonator having an arbitrary wavelength discrimination region satisfying the temperature adjustment condition.
  • the next invention is characterized in that in the above invention, there is provided a lens for adjusting a beam size of a laser beam emitted from the semiconductor laser, and outputting the adjusted optical signal to the Fry-Bri-Perot resonator. I do.
  • the present invention it is possible to adjust the beam size of the laser beam and make it incident on the Fabry-Perot resonator.
  • the wavelength detecting means directly detects a laser beam output from the semiconductor laser, and a first photodetector for detecting light transmitted through the Fabry-Perot resonator. It is characterized by comprising a second photodetector, and a wavelength detection unit that detects the oscillation wavelength of the laser light using the ratio of the detection signals of the first and second photodetectors.
  • the oscillation wavelength of the laser light is detected using the ratio of the detection signals of the first and second photodetectors, it is affected by the change in the output intensity of the semiconductor laser. It is possible to accurately detect the oscillation wavelength without the need.
  • the semiconductor laser and the Fabry-Perot resonator are mounted, and the first and the second light detectors are positioned so that the second photodetector is located above the first photodetector.
  • the laser light transmitted through the Fabry-Bale-One resonator is not received by the second photodetector, and the oscillation wavelength can be accurately detected.
  • the next invention is the above invention, wherein the semiconductor laser and the Fabry-Perot resonator are mounted, and the first photodetector is positioned above the first photodetector. And a base carrier on which a second photodetector is installed, wherein the laser light transmitted through the Fabry-Body resonator mounted on the base carrier is not received by the second photodetector.
  • the second photodetector is characterized in that it is disposed closer to the one side of the fabric port than the first photodetector.
  • the laser light transmitted through the Fabry-Perot resonator is not received by the second photodetector, and the oscillation wavelength can be accurately detected.
  • the next invention is directed to a wavelength monitoring device that monitors the wavelength of laser light output from a semiconductor laser, and is cut out so that the optical axis is inclined at a predetermined angle with respect to a plane perpendicular to the optical axis of the laser light. And a light reflecting film that reflects light on a surface on which the laser light is incident and a surface on which the laser light is emitted, and transmits transmitted light having a different transmission intensity according to the wavelength of the laser light.
  • a uniaxial birefringent crystal has a light reflection film that reflects light on a surface on which the laser light is incident and on a surface on which the laser light is emitted, and outputs transmitted light having different transmission intensity according to the wavelength of the laser light Second broadband And Perot resonator, characterized in that a wavelength detection means for measuring the oscillation wavelength of the first Oyopi laser beam based on transparently light of the second Fuaburipero resonator.
  • a Fabry-Perot resonator whose resonator length does not change in response to a temperature change can be configured by using a uniaxial birefringent crystal of one material, so that the configuration is simplified and a wavelength monitor is provided.
  • the laser wavelength is monitored using two fiber resonators for the narrow band and the wide band, so that the oscillation wavelength can be extremely accurately determined. Inspection Can be issued.
  • the laser beam output from the semiconductor laser is polarized in one direction, and the uniaxial laser constituting the first and second Fabry-Perot resonators is provided.
  • the refractive crystal has an optical axis in a plane parallel to a plane formed by the optical axis of the laser light and the polarization direction, and the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser light. It is characterized by.
  • the polarization of the laser light is aligned with the extraordinary optical axis, and a wavelength having two Fabry-Perot resonators having a temperature compensation function using a uniaxial birefringent crystal is provided. Monies can be realized.
  • the laser light output from the semiconductor laser is polarized in one direction
  • the uniaxial birefringent crystal forming the Fabry-Perot resonator is
  • the optical axis is in a plane perpendicular to a plane formed by the optical axis and the polarization direction, and the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser beam.
  • the present invention it is possible to realize a wavelength monitor having two Fabry-Perot resonators having a temperature compensating function by using a uniaxial biaxially-folded crystal of one material in which the polarization of laser light is aligned with the ordinary optical axis. it can.
  • the following invention is the invention according to the above invention, wherein the wavelength discrimination region of the second Fabry-Perot resonator for a wide band is larger than the wavelength variable region of the semiconductor laser, and the wavelength of the first Fabry-Perot resonator for a narrow band is The thickness in the optical axis direction of the uniaxial birefringent crystal constituting the first and second Fabry-Perot resonators so that the discrimination area is sufficiently smaller than the wavelength variable area of the first Fabry-Perot resonator. Is set.
  • two Fabry-Perot resonators for a narrow band and for a wide band are configured, so that a narrow band for a narrow band is easily provided.
  • Two Fabry-Perot resonators can be realized.
  • the wavelength detecting means is a first fiber.
  • a wavelength detector for detecting an oscillation wavelength of light is a first fiber.
  • the oscillation wavelength of the laser light is detected using the ratio of the detection signals of the first and second photodetectors and the ratio of the detection signals of the third and second photodetectors.
  • the oscillation wavelength can be extremely accurately detected without being affected by a change in the output intensity of the semiconductor laser.
  • the next invention is the above invention, in which the semiconductor laser and the Fabry-Perot resonator are mounted, and the second and third photodetectors are positioned above the first photodetector.
  • the second and third photodetectors are arranged closer to the Fabry-Perot resonator side than the first photodetector so as not to be performed.
  • the laser light transmitted through the Fabry-Bale-One resonator is not received by the second and third photodetectors, and the oscillation wavelength can be accurately detected.
  • FIG. 1 is a configuration diagram of a conventional wavelength monitoring device
  • FIG. 2 is a perspective view showing a conventional Fabry-Perot resonator
  • FIG. 3 is a configuration diagram of a wavelength monitoring device in the first embodiment.
  • FIG. 4 is a graph showing a change in transmittance with respect to wavelength of a Fabry-Perot resonator
  • FIG. 5 is a configuration diagram showing a Fabry-Perot resonator using a uniaxial birefringent crystal
  • FIG. 6 is a diagram showing a 3-BB
  • FIG. 7 is a graph showing the physical property values of the crystal
  • FIG. 1 is a configuration diagram of a conventional wavelength monitoring device
  • FIG. 2 is a perspective view showing a conventional Fabry-Perot resonator
  • FIG. 3 is a configuration diagram of a wavelength monitoring device in the first embodiment.
  • FIG. 4 is a graph showing a change in transmittance with respect to wavelength of a Fabry-
  • FIG. 7 is a graph showing the dependence of d ii / d T + an on the temperature T of the / 3-BBO crystal.
  • Figure 8 is a graph showing the dependence of the linear expansion coefficient a of the
  • Figure 9 shows the C3 of the extraordinary light refractive index ⁇ of the J3-BBO crystal.
  • Fig. 10 shows the dependence of the extraordinary refractive index of the crystal on the temperature dn / d ⁇ between the C-axis and the optical axis.
  • FIG. 13 is a configuration diagram illustrating a wavelength control device according to Embodiment 1
  • FIG. 13 is a configuration diagram illustrating a modification of the wavelength monitor device according to Embodiment 1
  • FIG. 14 is a wavelength diagram according to Embodiment 2 i.
  • FIG. 15 is a configuration diagram of a monitor device
  • FIG. 15 is a configuration diagram of a wavelength control device according to the second embodiment
  • FIG. 16 is a configuration diagram of a narrow-band Fabry-Perot resonator and a broadband filter.
  • Ripero is a graph showing the respective wavelength transmission characteristics one resonator
  • the first FIG. 7 is a block diagram showing a modification of the wavelength monitor device according to the second embodiment.
  • FIG. 3 is a configuration diagram showing a wavelength monitor (or a wavelength stabilized light source) according to Embodiment 1 of the present invention.
  • the semiconductor laser 1 emits laser light (hereinafter referred to as an optical signal) polarized in one direction.
  • Examples of the semiconductor laser 1 include a distributed feedback (DFB) laser having a diffraction grating in an active layer, a tunable laser diode whose wavelength can be changed by injection current or temperature, or an electroabsorption element and a laser diode. And a compound type (EA / LD) module in which the components are arranged in series. Further, the injection current or the temperature of the semiconductor laser 1 is changed by the control signal T1 input from the wavelength control device shown in FIG. 12, and the wavelength is controlled.
  • DFB distributed feedback
  • EA / LD compound type
  • An optical signal emitted from the semiconductor laser 1 is condensed by the lens 2 and output as parallel light.
  • This lens 2 adjusts the beam size of the optical signal
  • the incident light enters the resonator 3.
  • the axis connecting the center of the emission surface of the semiconductor laser 1 and the center of the lens 2 is the optical axis.
  • the traveling direction (optical axis direction) of an optical signal is defined as the Z-axis direction in space coordinates, and the upward direction in space is defined as the Y-axis direction.
  • the direction perpendicular to the axis and the Y axis (in Fig. 3, perpendicular to the plane of the paper and facing forward) is defined as the X axis. It is assumed that the optical signal emitted from the semiconductor laser 1 has a polarization component that vibrates in the X-axis direction.
  • the resonator 3 has reflecting films 7 and 8 for reflecting light on an incident surface on which an optical signal from the semiconductor laser 1 is incident and on an emitting surface on which the optical signal is emitted.
  • uniaxial birefringent crystal only e.g.,] 3 - BBO crystal, alpha -.
  • BBO crystal, L i I 0 3 crystal, C a C_ ⁇ 3 are formed by any force such as crystalline files Buripero resonator 3
  • the cut-out plane of the uniaxial birefringent crystal used as the material for the crystal is arranged so as to be parallel to the XY plane orthogonal to the optical axis, and the optical axis of the uniaxial birefringent crystal (hereinafter referred to as the C axis) is a laser. It is inclined at a predetermined angle with respect to the XY plane perpendicular to the optical axis of light.
  • the first photodiode (main photodetector) 4 receives the optical signal transmitted through the Fabry-Perot resonator 3, detects its intensity (photocurrent value), and outputs a light intensity monitor signal S1.
  • the second—photodiode (sub-photodetector) 5 is disposed above the first photodiode 4, and converts an optical signal emitted from the semiconductor laser 1 without passing through the cavity 3 and the resonator 3. It directly receives light, detects its intensity (photocurrent value), and outputs a light intensity monitor signal S2.
  • These semiconductor laser 1, lens 2, Fabry-Perot resonator 3, first photodiode 4, and second photodiode 5 are mounted on base carrier 6.
  • the height of the Fabry-Perot resonator 3 or the height of the second photodiode 5 is set so that the optical signal transmitted through the Fabry-Perot resonator 3 is not received by the second photodiode 5. Has been adjusted.
  • the transmission characteristics with respect to the wavelength of the optical signal transmitted through the Fabry-Perot resonator 3 are as follows: It is kept constant regardless of temperature changes. In other words, the Flipper Perot resonator 3 has a temperature compensation function. Next, the temperature compensation condition of the Fabry-Perot resonator 3 will be described.
  • an optical signal is vertically incident on the incident surface of a rectangular Fabry-Bore-One resonator 3.
  • the intensity reflectance is R
  • the dependence of the intensity of the optical signal transmitted through the Fabry-Perot resonator 3 on the wavelength with respect to the wavelength is given by: ) And Figure 4.
  • TR ( ⁇ ) is the transmittance.
  • the intensity of the optical signal transmitted through the Fabry-Perot resonator 3 changes periodically with respect to the frequency of the optical signal.
  • the frequency interval corresponding to one cycle is called a free spectral range (hereinafter, referred to as FSR, free spectral interval) with respect to the wavelength of the optical signal transmitted through the Fabry-Perot resonator 3.
  • FSR free spectral range
  • the FSR depends on the length of the resonator in the direction of the optical axis, the length in the case of FIG. 3, and the length L and the refractive index ⁇ of the uniaxial birefringent crystal 3 in the ⁇ -axis direction. 4)
  • c is the speed of light.
  • the temperature compensating condition for a Fabry-Perot single resonator is that the dependence of the intensity of the optical signal transmitted through the 2nL Fabry-Perot resonator 3 on the wavelength does not change with temperature. Therefore, to enable temperature compensation, it is necessary that the FSR expressed by equation (4) does not depend on temperature. In order for FSR to be constant with respect to temperature T, it is necessary in equation (4) that the resonator length n L has a constant value with respect to temperature T. Equation (5) expresses this relationship. W
  • a uniaxial birefringent crystal having one C-axis is used as the material of the Fabry-Perot resonator 3, and the positional relationship between the optical axis of the incident optical signal and the C-axis when the Fabry-Perot resonator 3 is used.
  • the linear expansion coefficient and the refractive index will be described.
  • the temperature compensation condition can be satisfied even when the polarization direction of the laser beam (in this case, the X direction) is aligned with the extraordinary or ordinary optical axis of the uniaxial birefringent crystal.
  • a case where the polarization direction of light is aligned with the extraordinary optical axis of a uniaxial birefringent crystal will be described.
  • the C axis of the uniaxial birefringent crystal which is the material of the Fabry-Perot resonator
  • the optical axis is parallel to the Z axis
  • the C axis is relative to the optical axis.
  • a certain angle ⁇ c is inclined.
  • the polarization of the optical signal incident on the Fabry-Perot resonator 3 is p-polarized with respect to the Fabry-Perot resonator 3 , and corresponds to the X direction in FIG.
  • the extraordinary ray has the same oscillating plane as the plane created by the C axis and the optical axis direction Therefore, in this case, the incident optical signal propagates as an extraordinary ray in the Fabry-Perot resonator 3.
  • the refractive index n for an extraordinary ray depends on the angle between the optical axis and the C axis, and ne and no depend on the temperature T. Therefore, they are expressed as n ( ⁇ c, T). become that way.
  • ne is the refractive index for the polarized light component in the direction parallel to the C axis (the extraordinary light refractive index), and no is the refractive index for the polarized light component in the direction perpendicular to the C axis (the ordinary light refractive index).
  • ⁇ ( ⁇ , ⁇ ) is the refractive index for an optical signal incident on a Fabry-Perot resonator made of a uniaxial birefringent crystal.
  • Equation (9) The linear expansion coefficient ⁇ of the axially birefringent crystal in the direction of the optical axis is expressed by equation (9). ac is the coefficient of linear expansion in the direction parallel to the C axis, and aa is the coefficient of linear expansion in the direction perpendicular to the C axis.
  • Fig. 6 shows the characteristics of] 3-BBO crystal. That is, the extraordinary refractive index ne of / 3—BBO is 1.531, the ordinary refractive index no is 1.6467, and the thermo-optic coefficient d no / dT in one 16. 8 X 10- 6 / K, the thermal-optic coefficient d ne / dT is _ 8. 8 X 10- 6 / a, coefficient of linear expansion ac is 33. 3X 10- 6 / K, the linear expansion The coefficient aa is 0 ⁇ 5 X 10 16 / K.
  • FIG. 7 shows the case where a uniaxial birefringent crystal composed of / 3-BBO is used as the Fabry-Perot resonator 3 and the polarization direction of the force laser beam is aligned with the extraordinary optical axis, and 3 ⁇ shown in equation (7).
  • 3 is a graph showing the relationship between ⁇ + ⁇ and the angle ⁇ c between the optical axis and the C axis.
  • Fig. 8 is a graph showing the dependence of the coefficient of linear expansion on the angle ⁇ c in one BBO crystal.
  • Fig. 9 is the graph showing the dependence of the refractive index n on the angle ⁇ c in a 0-BBO crystal.
  • FIG. 10 is a graph showing the dependence of dn / dT on the angle ⁇ c as stated by j3- BBO. That is, the relationship between the linear expansion coefficient ⁇ and the angle c in FIG. 8, the relationship between the refractive index ⁇ and the angle ⁇ c in FIG. 9, the relationship between dn / dT and the angle ⁇ c in FIG. Is used to obtain the relationship between 311/3 T + na and the angle ⁇ c shown in FIG.
  • the FSR is set to 10: 0 GHz (1.0 ⁇ 10 "Hz) corresponding to a wavelength fluctuation width of 0.8 nm of laser light.
  • the thickness L of the uniaxial birefringent crystal] 3-BBO in the Z-axis direction L 970 ⁇ m is obtained. It is a practical size.
  • an angle ⁇ ⁇ : that satisfies the equation (7) is obtained.
  • the refractive index n is calculated based on the following formula, and the length L of the uniaxial birefringent crystal 3 in the Z-axis direction is adjusted based on the equation (4) using the obtained angle ⁇ c and the refractive index n to obtain a desired value. Try to get FSR.
  • Equation (4) shows that a Fabry-Perot resonator with an arbitrary FSR that satisfies the temperature compensation condition can be made.
  • the optical signal emitted from the semiconductor laser 1 is focused on the lens 2.
  • the upper part of the collected optical signal is directly received by the second photodiode 5.
  • the second photodiode 5 detects and monitors the intensity of the received optical signal.
  • An output control circuit (not shown) controls the optical output of the semiconductor laser 1 to be constant based on the difference between the intensity monitor signal S2 and a preset optical signal intensity.
  • the intensity of the optical signal emitted from the Fabry-Perot resonator 3 has a wavelength discrimination characteristic as shown in Equation (3.), and the characteristic is kept constant irrespective of the temperature change of the crystal. Has temperature compensation function.
  • the first photodiode 4 detects the intensity of the optical signal passing through the Fabry-Perot resonator 3, and outputs an optical intensity monitor signal S1.
  • the second photodiode 5 directly detects the optical signal intensity emitted from the semiconductor laser 1 and outputs the optical intensity monitor signal S2, as described above.
  • These light intensity monitor signals S 1 and S 2 are sent to the wavelength controller 50 shown in FIG.
  • the wavelength controller 50 detects the wavelength of the optical signal, and controls the semiconductor laser 1 such that the detected wavelength matches a preset wavelength (for example, the reference wavelength 0 in FIG. 4).
  • FIG. 12 is a configuration diagram of the wavelength control device 50.
  • the wavelength controller 50 includes a wavelength detector 51 and a laser controller 52.
  • the wavelength detector 51 receives light intensity monitor signals from the first and second photodiodes. Signals S 1 and S 2 and a preset reference wavelength; L 0 are input.
  • the wavelength detector 51 obtains the oscillation wavelength of the optical signal emitted from the semiconductor laser 1 based on the light intensity monitor signals S1 and S2, and obtains the difference between the oscillation wavelength and the reference wavelength I0.
  • the difference between the reference wavelength; L 0 from the wavelength detector 51 and the oscillation wavelength emitted from the semiconductor laser 1 is input to the laser controller 52.
  • the laser control unit 52 obtains a control signal ⁇ 1 for controlling the temperature, injection current, and the like of the semiconductor laser 1 so that the oscillation wavelength coincides with the reference wavelength ⁇ 0 according to the difference. 1 is output to the semiconductor laser 1.
  • Fig. 4 The relationship between the transmittance and the wavelength of the Fabry-Perot resonator 3 is shown in Fig. 4.
  • L0 in Fig. 4 the case where the oscillation wavelength is adjusted to the reference wavelength; L0 in Fig. 4 will be described.
  • the value of the light intensity monitor signal S 1 detected by the first photodiode 4 becomes smaller as the wavelength of the optical signal shifts to the longer wavelength side. It can be seen that the shift to the short wavelength side increases, and the change in the light intensity monitor signal S1 accompanying the change in the wavelength is monitored, and the shift from the reference wavelength;
  • the light intensity monitor signal S2 that directly detects the optical signal emitted from the semiconductor laser 1 and the light intensity monitor signal S1 that detects the optical signal transmitted through the Fabry-Perot resonator 3 are the semiconductor laser It changes in proportion to the intensity of the optical signal emitted from 1.
  • the wavelength of the optical signal emitted from the semiconductor laser 1 includes the wavelength ⁇ 0. If it is within the range, the value of the signal intensity ratio S1 / S2 indicates the wavelength of the optical signal.
  • the half of the FSR is sufficiently larger than the wavelength tunable region of the semiconductor laser 1 and the wavelength tunable region is included in one slope including L0, The Brillouin resonator 3 can be used as an absolute wavelength monitor.
  • the signal intensity ratio S 1 / S 2 at the reference wavelength 0 is obtained in advance, and the signal intensity ratio S 1 / S 2 at the reference wavelength ⁇ 0 is stored in the wavelength detector 51.
  • the wavelength detector 51 In the wavelength detector 51, the stored reference wavelength; the signal intensity ratio S 1 / S 2 at I 0, and the light intensity monitor signals S 1, S S from the first and second photodiodes 4 and 5 The difference (deviation) between the oscillation wavelength and the reference wavelength; L 0 is calculated by calculating the difference between the signal intensity ratio S 1 / S 2 obtained based on Step 2. The calculated deviation signal is input to the laser control unit 52.
  • the laser controller 52 uses the deviation signal input from the wavelength detector 1 to output a control signal ⁇ 1 for changing the value of the temperature, the injection current, or the like to the semiconductor laser 1, thereby controlling the semiconductor laser 1. Control the wavelength.
  • the oscillation wavelength of the semiconductor laser 1 becomes longer.
  • the laser control unit 52 receives the deviation signal from the wavelength detection unit 51 and the oscillation wavelength is shifted to a longer wavelength side than the reference wavelength, the injection current into the semiconductor laser 1 is increased. If the oscillation wavelength is shifted to a shorter wavelength side than the reference wavelength, a control signal ⁇ 1 for increasing the injection current to the semiconductor laser 1 is sent to the semiconductor laser 1. -When controlling the wavelength by changing the temperature of the semiconductor laser 1, generally, the higher the temperature is, the longer the oscillation wavelength of the semiconductor laser 1 is.
  • the laser control section 52 receives the deviation signal from the wavelength detection section 51, if the oscillation wavelength is shifted to a longer wavelength side than the reference wavelength, the temperature of the semiconductor laser 1 is increased, and If the wavelength is shifted to a shorter wavelength side than the reference wavelength, a control signal # 1 for lowering the temperature of the semiconductor laser 1 is sent to the semiconductor laser 1.
  • the polarization direction of the laser light is ⁇ polarization.
  • s-polarized laser light that is, laser light having a polarization direction perpendicular to the plane formed by the C axis and the optical axis.
  • the temperature compensation of equation ( 7) The condition can be satisfied. That is, the above equation (7) is satisfied for both the ordinary optical axis and the extraordinary optical axis. In this way, when the polarization direction of the laser light is aligned with the ordinary optical axis, in other words, the C axis is set in a plane perpendicular to the plane formed by the optical axis and the polarization direction of the laser light.
  • the angle ⁇ c between the optical axis and the C axis is 57.05 degrees.
  • the refractive index n and dn / dt when the ordinary optical axis is used do not depend on the angle ⁇ c and always take a constant value. Then, in this case, only the coefficient of linear expansion in equation (7) changes with the angle ⁇ c.
  • the first embodiment constitute a Fabry base mouth one resonator 3 Lou Jikusei birefringent crystal (e.g. - BBO (B aB 2 0 4 )) , and the laser beam C axis In the plane formed by the optical axis and the direction of polarization of the optical axis, and in the plane perpendicular to the plane, the force is arranged so that the C axis has a constant inclination with respect to the optical axis.
  • Lou Jikusei birefringent crystal e.g. - BBO (B aB 2 0 4 )
  • the resonator 3 can have a temperature compensation function (a function in which the intensity of the signal light emitted from the resonator 3 does not depend on the temperature), and the light intensity monitor signal S depends only on the wavelength of the optical signal. 1 can be detected and monitored. Further, the wavelength of the optical signal emitted from the semiconductor laser 1 can be controlled to a desired reference wavelength ⁇ 0 based on the detected light intensity monitor signal S 1. Furthermore, since only a uniaxial birefringent crystal of one material is used, the configuration of the semiconductor laser device can be simplified, and since the configuration is simplified, the reliability as a wavelength monitor can be improved. Become.
  • the physical constants of ⁇ -BBO are: extraordinary refractive index ne is 1.53003, ordinary refractive index no is 1.6650, and thermo-optic coefficient d no / d T is -9.3 X 1 0 one 6 / K, a thermal optical coefficient d ne / dT is 1 6. 6 X 10- 6 / K , the linear expansion coefficient in 36. 0 X 10_ 6 / K, the linear expansion coefficient 4. 0X 10- 6 / K.
  • the temperature compensation conditional expression (7) can be satisfied even when a crystal of Li IO 3 is used as the material of the Fabry-Perot resonator 3 in FIG.
  • FIG. 11 is abnormal to the optical axis of the laser light when aligned in polarization is a graph showing the dependence on the angle [psi c of dn / dT + ⁇ showing the expression (7) of the L i 10 3 crystals.
  • the first 1 by the FIG lever, L i I 0 3 with crystal, when aligned polarization of the laser beam on the extraordinary optical axis, the angle that satisfies the temperature compensation condition dn / dT + a n 0 ⁇ c Can be determined to be 22.70 degrees.
  • the angle satisfying the temperature compensation condition dn / dT + an-O ⁇ c is 18.65 degrees.
  • a C a C 3 crystal can be used as the uniaxial birefringent crystal.
  • any other uniaxial birefringent crystal may be used as long as the material satisfies the temperature compensation conditional expression (7) for the Fabry-Perot resonator.
  • the wavelength monitoring device shown in FIG. 12 with the wavelength monitoring device shown in FIG. 3, it is possible to configure a wavelength stabilized light source.
  • the thirteenth excavation is a configuration diagram showing a wavelength monitor according to a modification of the first embodiment of the present invention.
  • the second photodiode 5 located above the Fabry-Perot resonator 3 is arranged ahead of the first photodiode 4 so as to reduce the distance from the lens 2. That is, in this case, the location where the second photodiode 5 of the base carrier 6 is installed is protruded toward the semiconductor laser 1, and the location where the first photodiode 4 of the base carrier 6 is installed is A step is formed between the base carrier 6 and the position where the second photodiode 5 is installed.
  • the second photodiode 5 is arranged ahead of the first photodiode 4, even if the optical signal is (4) Even if the light is scattered on the bottom surface of the base carrier 6 after being incident on the single-cavity 3, the scattered light is not received by the second photodiode 5 after passing through the Fabry-Perot resonator 3.
  • each photodiode monitors the wavelength and the intensity of the optical signal.
  • three photodiodes are arranged independently, and two Fabry-Perot resonators are vertically arranged in parallel, so that the three photodiodes arranged in three are arranged.
  • Two photodiodes are used to monitor the wavelength of an optical signal in a wide band or a narrow band, and one photodiode is used to monitor an optical intensity signal.
  • FIG. 14 is a configuration diagram showing a wavelength monitor device according to Embodiment 2 of the present invention.
  • the same components as those of the wavelength monitoring device of the first embodiment are denoted by the same reference numerals, and the description of those portions will be omitted.
  • the temperature and injection current of the semiconductor laser 1 are controlled by the control signal T1 sent from the wavelength control device 60 shown in FIG. 15 to control the wavelength.
  • the Fabry-Bellow resonator 21 is made of a uniaxial birefringent crystal (eg, -B-) cut out to have the temperature compensation function shown in the first embodiment. It has reflection films 23 and 24 on its entrance surface and exit surface.
  • the third photodiode 22 detects the intensity of the optical signal transmitted through the Fabry-Perot resonator 21, and is arranged between the first photodiode 4 and the second photodiode 5.
  • the optical signal emitted from the semiconductor laser ⁇ ⁇ is condensed by the lens 2 and converted into parallel light.
  • First Photo Diode 4 the intensity of the optical signal transmitted through the Fabry-Perot resonator (for narrow band) 3 is detected, and the intensity of the optical signal transmitted through the Fabry-Perot resonator (for wide band) 21 is detected in the third photodiode 22.
  • the light intensity monitor signal detected by the first photodiode 4 is S1
  • the light intensity monitor signal detected by the third photodiode 22 is S3
  • the light intensity monitor signal is detected by the second photodiode 5.
  • the light intensity monitor signal is S2.
  • the light intensity monitor signals S1, S2 and S3 are sent to the wavelength control device 60 shown in FIG.
  • the wavelength control device 60 detects the oscillation wavelength using these signals S1, S.2, and S3, and controls the control signal for controlling the wavelength of the optical signal emitted from the semiconductor laser 1 based on the detected wavelength. T 1 is formed, and this control signal ⁇ 1 is output to the semiconductor laser 1.
  • FIG. 16 shows the wavelength transmission characteristics of the narrow-band Fabry-roll resonator 3 and the wide-band Fabry-low resonator 21.
  • the FSR of the Fabry-Perot resonator 3 for the narrow band is very small compared to the FSR of the Fabry-Perot resonator 21 for the wide band so that Set the length.
  • half of the FSR of the Fabry-Perot resonator 21 for a wide band that is, the wavelength discrimination region is larger than the wavelength tunable range of the semiconductor laser 1, and the wavelength tunable range of the semiconductor laser 1 is one slope in the FSR of the Fabry-Perot resonator 21.
  • the Fabry-Perot resonator 3 for narrow band has an FSR of 20 THz, and the intensity reflectance of the reflective film is 30. /. It is assumed that the FSR of the broadband Fabry-Perot resonator 21 is 100 GHz and the intensity reflectance of the reflection film is 30%.
  • the wavelength control device 60 includes a wavelength detection unit 61 and a laser control unit 52.
  • the wavelength detector 61 receives light intensity monitor signals S 1, S 2, S 3 from the first to third photodiodes 4, 5, and 22 and a reference wavelength ⁇ 0.
  • the wavelength detecting unit 61 obtains the oscillation wavelength of the optical signal emitted from the semiconductor laser 1 based on the light intensity monitor signals S1, S2, and S3, and obtains the difference between this oscillation wavelength and the reference wavelength ⁇ 0.
  • Laser controller The difference between the reference wavelength ⁇ 0 from the wavelength detector 61 and the oscillation wavelength emitted from the semiconductor laser 1 is input to 52, and the laser controller 52 sets the oscillation wavelength as a reference according to the difference.
  • a control signal ⁇ 1 ⁇ for controlling the temperature, injection current, and the like of the semiconductor laser 1 is determined so as to match the wavelength; L 0, and the control signal ⁇ 1 is output to the semiconductor laser 1.
  • the wavelength detector 61 detects a deviation from the reference wavelength; L0 using the light intensity monitor signal S3 transmitted through the Fabry-Perot resonator 21 for a wide band. That is, as described above, the wavelength detection unit 61 is configured to calculate the signal intensity ratio S 1 / S 2 at the reference wavelength previously obtained using the wavelength transmission characteristics of the Fabry-Perot resonator 21 for a wide band. And the signal intensity ratio S 3 / S 2 obtained based on the light intensity monitor signals S 2, S 3 from the second and third photodiodes 5, 22 to obtain the oscillation wavelength and the reference Calculate the deviation (deviation) from the wavelength; L 0.
  • this deviation amount is larger than the slope width of the narrow-band Fabry-Bore-One resonator 3, this value is sent to the laser control unit 52 as it is.
  • the reference wavelength calculated using the light intensity monitor signals S3 and S2; if the deviation from I0 is smaller than the slope width of the narrow-band fiber-optic resonator 3, narrow band
  • the oscillation wavelength is detected with higher accuracy by calculating again the amount of deviation from the reference wavelength; I0 using the slope characteristic of the fiber optic resonator 3 for use.
  • a reference wavelength calculated in advance using the wavelength transmission characteristics of the Fabry-Perot resonator 3 for the narrow band; the signal intensity ratio S 1 / S 2 at L 0, and the first and second photodiodes 4 and 5
  • the difference (deviation) between the oscillation wavelength and the reference wavelength ⁇ 0 is calculated by calculating the difference between the signal intensity ratio S 3 / S 2 obtained based on the light intensity monitor signals S 1 and S 2 from.
  • the deviation amount (deviation signal) thus obtained is sent to the laser control unit 52.
  • Laser control unit 52 operates in the same manner as in the first embodiment. That is, the laser control unit 52 outputs a control signal ⁇ 1 for changing the value of the temperature or the injection current to the semiconductor laser 1 using the deviation signal input from the wavelength detection unit 61.
  • the wavelength of the semiconductor laser 1 is controlled. Since one slope in the FSR of the Fabry-Perot resonator 21 for a wide band is larger than the wavelength tunable region of the semiconductor laser 1, the absolute wavelength can be monitored over a wide band. However, as shown in FIG. 16, the wavelength transmission characteristic of the Fabry-Perot resonator 21 for a wide band is more variable than the wavelength transmission characteristic of the Fabry-Perot resonator 3 for a narrow band. Eich is small. That is, the light intensity monitor signal S3 has a smaller signal intensity change with respect to the wavelength change than the light intensity monitor signal S1.
  • the wavelength of the optical signal emitted from the semiconductor laser 1 can be fixed more accurately by using the optical signal intensity S1 transmitted through the Fabry-Perot resonator 3, which is a wavelength monitor for a narrow band.
  • the resonators of the resonators 3 and 21 are arranged such that the lower Fabry-Perot resonator 3 is used as a wavelength monitor for a wide band and the upper Fabry-Perot resonator 21 is used as a wavelength monitor for a narrow band.
  • the length may be adjusted.
  • the absolute wavelength of the optical signal emitted from the semiconductor laser 1 can be controlled with high accuracy over a wide band.
  • a wavelength stabilized light source can be configured by combining the wavelength monitor shown in FIG. 15 with the wavelength monitor shown in FIG.
  • FIG. 17 is a configuration diagram showing a wavelength monitor according to a modification of the second embodiment of the present invention.
  • the second and third photodiodes 5, 22 located above the Fabry-Perot resonator 3 are connected to the first photodiode so as to reduce the distance from the lens 2. It is arranged before diode 4.
  • the location where the second and third photodiodes 5 and 22 of the base carrier 6 are installed is configured to protrude toward the semiconductor laser 1, and the first photodiode of the base carrier 6 is formed.
  • a step is formed between the place where the diode 4 is installed and the place where the second and third photodiodes 5 and 22 of the base carrier 6 are installed. are doing.
  • This invention is suitable for use as a wavelength monitor device of a semiconductor laser as a light source used in wavelength division multiplexing (WDM) communication using an optical fiber and high-density wavelength division multiplexing (DWDM) communication.
  • WDM wavelength division multiplexing
  • DWDM high-density wavelength division multiplexing

Abstract

A wavelength monitor device comprising a Fabry-Perot resonator (3) constructed by using a one-material uniaxial double-refraction crystal so cut out that the optical axis thereof is tilted a specified angle with respect to a plane perpendicular to the light axis of a laser beam, and wavelength detecting means (4, 5, 51) for measuring the oscillation wavelength of a laser beam based on a transmitting light of the resonator (3), whereby it is possible to configure a Fabry-Perot resonator (3) that is free from a temperature-dependent change in the length of the resonator despite its simple configuration and that can detect an oscillation wavelength with a high accuracy.

Description

明 細 書  Specification
波長モニタ装置 Wavelength monitor
技術分野 Technical field
この発明は、 波長分割多重伝送 （WDM)方式などに用いられるレーザ光の波 長をモニタする波長モニタ装置に関し、 特にフアブリペロー共振器を通過させた レーザ光を検出することによりレーザ光の発振波長を測定する波長モニタ装置に 関する のである。  The present invention relates to a wavelength monitoring device that monitors the wavelength of a laser beam used in a wavelength division multiplexing transmission (WDM) system or the like, and in particular, detects the laser beam that has passed through a Fabry-Perot resonator to reduce the oscillation wavelength of the laser beam. It relates to the wavelength monitoring device to be measured.
' 背景技術 '' Background technology
第 1図は、 特開平 0 3 - 1 6 0 7 7 4号公報に示された従来の波長モニタ装置 を示す構成図である。 第 1図において、 半導体レーザ 1 0 1は出射する光信号の 波長を制御することができるものである。 半導体レーザ 1 0 1より発射された光 は、.光学レンズ 1 0 5により平行光に変換され、 平行光はさらにビームスプリッ タ 1 0 6により 2方向に分岐される。 分岐された一方の光はレンズ 1 0 7を介し、 光検出器 1 0 8例えばフォトダイォードに集光される。 他方の光は、 フアブリべ ロー共振器 1 1 1に入射する。 フアブリペロー共振器 1 1 1は、 反射膜 1 0 9、 1 1 0を有し、 2種類の光学材料で形成されている。 フアブリペロー共振器 1 1 1を透過した光は、 レンズ 1 1 2を介し、 光検出器 1 1 3に集光される。  FIG. 1 is a configuration diagram showing a conventional wavelength monitor device disclosed in Japanese Patent Application Laid-Open No. H03-160774. In FIG. 1, a semiconductor laser 101 can control the wavelength of an emitted optical signal. The light emitted from the semiconductor laser 101 is converted into parallel light by the optical lens 105, and the parallel light is further split into two directions by the beam splitter 106. One of the branched lights is focused on a photodetector 108, for example, a photodiode via a lens 107. The other light is incident on the Fabry-Bellows resonator. The Fabry-Perot resonator 111 has reflection films 109 and 110 and is made of two kinds of optical materials. The light transmitted through the Fabry-Perot resonator 111 is focused on the photodetector 113 via the lens 112.
第 2図は第 1図におけるフアブリペロー共振器 1 1 1の構成図である。 1種類 の光学材料で形成されたフアブリペロー共振器の温度係数 γは式 （1 ) であらわ される。 ここで、 ηは光学材料の屈折率、 αは光線方向の線膨張率である。 FIG. 2 is a configuration diagram of the Fabry-Perot resonator 111 in FIG. The temperature coefficient γ of a Fabry-Perot resonator made of one type of optical material is expressed by equation (1). Here, η is the refractive index of the optical material, and α is the linear expansion coefficient in the light ray direction.
γγ
Figure imgf000003_0001
の温度係数 T/がゼロになれば、 フアブリペロー共振器 1 1 1の共振器長は温 度に応じて変化せず、 半導体レーザ 101から出射され、 フアブリペロー共振器 1 1 1を透過した光強度の波長依存性も変化しないので、 共振器 111の温度に 関係無く正確に波長をモニタすることができる。 この温度係数 γをゼロにするた めに、 フアブリペロー共振器 111は、 温度係数 γの符号が互いに異なる2種類 の光学材料で構成される。 フアブリペロー共振器 111全体の温度係数をゼロに するためには、 式 （2) を満たす必要がある。
Figure imgf000003_0001
If the temperature coefficient T / becomes zero, the Fabry-Perot resonator length becomes Because the wavelength dependence of the light intensity emitted from the semiconductor laser 101 and transmitted through the Fabry-Perot resonator 111 does not change depending on the temperature, the wavelength is accurately monitored irrespective of the temperature of the resonator 111. Can be. In order to make the temperature coefficient γ zero, the Fabry-Perot resonator 111 is composed of two kinds of optical materials having different signs of the temperature coefficient γ. In order to make the temperature coefficient of the entire Fabry-Perot resonator 111 zero, it is necessary to satisfy Expression (2).
Γΐη 01 ^01 + Γ2η 02 ^02 = 0 (2) ここで、 n。い 101はそれぞれ第 1の光学材料の屈折率および物理長、 r xは 第 1の光学材料の式 （ 1 ) による温度係数である。 また、 n。 2， 102はそれぞ れ第 2の光学材料の屈折率および物理長、 r 2は第 2の光学材料の温度係数であ る。 フアブリペロー共振器 1 1 1を実際に構成するのに、 温度係数^正の値を持 つ光学材料として、 石英を用い、 温度係数が負の値を持つ光学材料としてルチル を用いた場合、 それぞれの C軸 （光学軸） が光軸と同じ方向を向いているとする と、 ルチルの温度係数の絶対値が石英の温度係数の絶対値の 2. 7倍となること から、 |n011。J:|n021。2| = 2. 7 : 1という関係を満たす。 Γ η η 01 ^ 01 + Γ 2 η 02 ^ 02 = 0 (2) where n. 101 is the refractive index and physical length of the first optical material, respectively, and r x is the temperature coefficient of the first optical material according to the equation (1). Also n. 2, 1 02 the refractive index and physical length of the second optical material, respectively it, r 2 is Ru temperature coefficient der of the second optical material. In order to actually construct the Fabry-Perot resonator 111, when quartz is used as the optical material having a temperature coefficient ^ positive value and rutile is used as the optical material having a negative temperature coefficient, When the C-axis (optical axis) and are oriented in the same direction as the optical axis, since the absolute value of the temperature coefficient of the rutile is 2.7 times the absolute value of the temperature coefficient of the quartz, | n 01 1. J: | n 02 1. 2 | = 2. 7 : 1
ここで、 n。い 101は水晶の屈折率おょぴ物理長、 n。2， 1。2はルチルの屈 折率および物理長である。 式 （2) を満たすようにそれぞれの物理長を調整する ことにより、 共振器長 L = n01101 + n021。2の変化しないフアブリペロー共 振器を構成することが可能である。 Where n. There 1 01 is the refractive index of your Yopi physical length of the crystal, n. Two , one. 2 is the refractive index and physical length of rutile. By adjusting the respective physical lengths to satisfy equation (2), the resonator length L = n 01 1 01 + n 02 1. It is possible to configure two unchanged Fabry-Perot resonators.
上記従来技術では、 温度係数の符号が異なる 2個の光学材料を用いて、 温度に 対して共振器長が変化しなレ、ようなフアブリべ口一共振器を構成しているため、 2個の光学材料を張り合わせる必要がある。 2個の光学材料を張り合わせる際に は、 それぞれの材料の屈折率差による接合面での反射および、 接着剤と光学材料 の屈折率差による接合面における反射を考慮に入れる必要があり、 光学材料もし くは接着剤の組み合わせについて検討を行う必要があり、 各種の面倒な調整作業 を行う必要がある。 In the above prior art, two optical materials having different signs of the temperature coefficient are used to form a Fabry-Bore-One resonator in which the resonator length does not change with temperature. It is necessary to laminate optical materials. When bonding two optical materials, it is necessary to take into account reflection at the joint surface due to the refractive index difference between the two materials and reflection at the joint surface due to the refractive index difference between the adhesive and the optical material. It is necessary to consider the combination of materials and adhesives, and various complicated adjustments are required. Need to do.
この発明は、 上記に鑑みてなされたもので、 一材料の一軸性複屈折結晶を用い て、 温度変化に応じて共振器長の変化しないフアブリペロー共振器を構成し、 こ れにより構成が単純化され、 大量生産を実現することができるフアブリペロー共 振器を用いた波長モニタ装置を得ることを目的とする。  The present invention has been made in view of the above, and comprises a Fabry-Perot resonator whose resonator length does not change in response to a temperature change, using a uniaxial birefringent crystal of one material, thereby simplifying the configuration. It is an object of the present invention to obtain a wavelength monitor using a Fabry-Perot resonator that can realize mass production.
発明の開示 Disclosure of the invention
この発明では、 半導体レーザから出力されるレーザ光の波長をモニタする波長 モニタ 置において、 前記レーザ光の光軸に垂直な面に対して光学軸が所定角度 傾くように切り出された一材料の一軸性複屈折結晶から成り、 前記レーザ光が入 射する面と出射する面とに光を反射する光反射膜を有し、 上記レーザ光の波長に 応じて異なる透過強度を有する透過光を出力するフアブリペロー共振器と、 前記 フアブリペロー共振器の透過光に基づきレーザ光の発振波長を測定する波長検出 手段とを備えたことを特徴とする。  According to the present invention, in a wavelength monitor device for monitoring the wavelength of laser light output from a semiconductor laser, one axis of one material cut out so that an optical axis is inclined at a predetermined angle with respect to a plane perpendicular to the optical axis of the laser light. A light reflecting film that reflects light on a surface on which the laser light enters and a surface on which the laser light exits, and outputs transmitted light having different transmission intensities according to the wavelength of the laser light. A Fabry-Perot resonator; and wavelength detecting means for measuring an oscillation wavelength of laser light based on light transmitted through the Fabry-Perot resonator.
この発明によれば、 一材料の一軸性複屈折結晶を用いて、 温度変化に応じて共 振器長の変化しないファプリぺロ一共振器を構成することができるので、 構成が 単純化され、 波長モニタとしての信頼性が向上するとともに、 生産時に面倒な調 整作業 行わなくてもよくなり、 大量生産を実現することができる。  According to the present invention, it is possible to configure a Fabry-Perot resonator in which the resonator length does not change in response to a temperature change by using a uniaxial birefringent crystal of one material, so that the configuration is simplified, The reliability as a wavelength monitor is improved, and troublesome adjustment work is not required during production, and mass production can be realized.
つぎの発明は、 上記の発明において、 前記半導体レーザから出力されるレーザ 光は、 一方向に偏光されたものであり、 上記フアプリペロー共振器を構成する一 軸性複屈折結晶は、 前記レーザ光の光軸と偏光方向とで作られる平面に対し平行 な面内に光学軸があり、 この光学軸がレーザ光の光軸に対し所定の角度傾いてい ることを特徴とする。  In the following invention, in the above invention, the laser light output from the semiconductor laser is polarized in one direction, and the uniaxial birefringent crystal constituting the Floupe Perot resonator is The optical axis is in a plane parallel to a plane formed by the optical axis and the polarization direction, and the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser beam.
この発明によれば、 異常光軸にレーザ光の偏光を揃えており、 一材料の一軸性 複屈折結晶を用いて、 温度補償機能を持つフアブリペロー共振器を持つ波長モニ タを実現することができる。  According to the present invention, the wavelength of the laser beam is aligned with the extraordinary optical axis, and a wavelength monitor having a Fabry-Perot resonator having a temperature compensation function can be realized using a uniaxial birefringent crystal of one material. .
つぎの発明は、 上記の発明において、 前記半導体レーザから出力されるレーザ 光は、 一方向に偏光されたものであり、 上記フアブリペロー共振器を構成する一 軸性複屈折結晶は、 前記レーザ光の光軸と偏光方向とで作られる平面に対し垂直 な面内に光学軸があり、 この光学軸がレーザ光の光軸に対し所定の角度傾いてい ることを特徴とする。 The following invention is the above invention, wherein the laser output from the semiconductor laser is The light is polarized in one direction, and the uniaxial birefringent crystal constituting the Fabry-Perot resonator has an optical axis in a plane perpendicular to a plane formed by the optical axis and the polarization direction of the laser light. The optical axis is inclined at a predetermined angle with respect to the optical axis of the laser beam.
この発明によれば、 常光軸にレーザ光の偏光を揃えており、 一材料の一軸性複 屈折結晶を用いて、 温度捕償機能を持つフアブリペロー共振器を持つ波長モニタ を実現することができる。  According to the present invention, it is possible to realize a wavelength monitor having a Fabry-Perot resonator having a temperature compensation function by using a uniaxial birefringent crystal of one material in which the polarization of laser light is aligned with the ordinary optical axis.
つぎの発明は、 上記の発明において、 前記フアブリペロー共振器を構成する一 軸性複展折結晶は、 一軸性複屈折結晶の屈折率、 光軸方向の線膨張係数および熱 光学係数に基づき、 光学軸の光軸に対-する角度が設定されていることを特徴とす る。  In the following invention, in the above invention, the uniaxial birefringent crystal constituting the Fabry-Perot resonator is based on a refractive index of the uniaxial birefringent crystal, a linear expansion coefficient in an optical axis direction, and a thermo-optic coefficient. An angle of the axis with respect to the optical axis is set.
この発明によれば、 その屈折率、 光軸方向の線膨張係数および熱光学係数に基 づき、 光学軸の光軸に対する角度が設定された一軸性複屈折結晶を用いているの で、 一材料の一軸性複屈折結晶を用いて、 温度補償機能を持つフアブリペロー共 振器を持つ信頼性の高レ、波長モニタを実現することができる。  According to the present invention, a uniaxial birefringent crystal in which the angle of the optical axis with respect to the optical axis is set based on the refractive index, the coefficient of linear expansion in the optical axis direction, and the thermo-optic coefficient is used. Using a uniaxial birefringent crystal, a highly reliable wavelength monitor with a Fabry-Perot resonator having a temperature compensation function can be realized.
つぎの発明は、 上記の異常光軸にレーザ光の偏光を揃える発明の場合において、 上記ファプリペロー共振器を構成する一軸性複屈折結晶は、 一軸性複屈折結晶の 屈折率ど光軸方向の線膨張係数との積と、 熱光学係数との和が零に一致するよう に光学軸の光軸に対する角度が設定されていることを特徴とする。  In the next invention, in the case of the invention in which the polarization of the laser light is aligned with the above-mentioned extraordinary optical axis, the uniaxial birefringent crystal constituting the Fabry-Perot resonator has a line in the optical axis direction such as the refractive index of the uniaxial birefringent crystal. The angle of the optical axis with respect to the optical axis is set so that the sum of the product of the expansion coefficient and the thermo-optic coefficient coincides with zero.
この発明によれば、 異常光軸にレーザ光の偏光を揃える場合、 屈折率と光軸方 向の線膨張係数との積と、 熱光学係数との和が零に一致するように光学軸の光軸 に対する角度が設定されている一軸性複屈折結晶を用いているので、 高精度の温 度補償機能を持つファブリぺ口一共振器を持つ波長モニタを実現することができ る。  According to the present invention, when aligning the polarization of the laser light with the extraordinary optical axis, the optical axis is adjusted so that the sum of the product of the refractive index and the linear expansion coefficient in the optical axis direction and the thermo-optic coefficient becomes zero. Since a uniaxial birefringent crystal whose angle to the optical axis is set is used, it is possible to realize a wavelength monitor having a Fabry-Earth single resonator having a highly accurate temperature compensation function.
つぎの発明は、 上記の常光軸にレーザ光の偏光を揃える発明の場合において、 上記ファブリペロー共振器を構成する一軸性複屈折結晶は、 一軸性複屈折結晶の 屈折率と光軸方向の線膨張係数との積と、 熱光学係数との和が零に一致するよう に光学軸の光軸に対する角度が設定されていることを特徴とする。 In the next invention, the uniaxial birefringent crystal constituting the Fabry-Perot resonator has a refractive index of the uniaxial birefringent crystal and a line extending in the optical axis direction. The sum of the product of the expansion coefficient and the thermo-optic coefficient must be equal to zero. The angle of the optical axis with respect to the optical axis is set.
この発明によれば、 常光軸にレーザ光の偏光を揃える場合、 屈折率と光軸方向 の線膨張係数との積と、 熱光学係数との和が零に一致するように光学軸の光軸に 対する角度が設定されている一軸性複屈折結晶を用いているので、 高精度の温度 補償機能を持つフアブリぺロ一共 ¾器を持つ波長モニタを実現することができる。 つぎの発明は、 上記の異常光軸にレーザ光の偏光を揃える発明の場合において、 前記フアブリペロー共振器を構成する一軸性複屈折結晶を、 α— ΒΒΟ、 β - BO、 L i I 03のいずれかとし、 α— ΒΒΟの場合は、 光学軸の光軸に対する 角度を 4. 3 5度とし、 /3— ΒΒΟの場合は、 光学軸の光軸に対する角度を 6 4. 75度とし、 L i 103の場合は、 光学軸の光軸に対する角度を 22. 70度 とすることを特敷とする。 According to the present invention, when aligning the polarization of the laser light with the ordinary optical axis, the optical axis of the optical axis is adjusted so that the sum of the product of the refractive index and the linear expansion coefficient in the optical axis direction and the thermo-optic coefficient coincides with zero. Since a uniaxial birefringent crystal having an angle with respect to is used, it is possible to realize a wavelength monitor having a fabricator having a high-precision temperature compensation function. In the next invention, in the case of the invention in which the polarization of the laser light is aligned with the above-mentioned extraordinary optical axis, the uniaxial birefringent crystal constituting the Fabry-Perot resonator is formed of α-ΒΒΟ, β-BO, and L i I 0 3 . In the case of α-ΒΒΟ, the angle of the optical axis with respect to the optical axis is 4.35 degrees, and in the case of / 3-—, the angle of the optical axis with respect to the optical axis is 6 4.75 degrees, L for the i 10 3, and Tokushiki that the angle 22.70 degrees with respect to the optical axis of the optical axes.
この発明によれば、 異常光軸にレーザ光の偏光を揃え、 また、 一軸性複屈折結 晶として、 α— BBO、 j3 _BBO、 L i I 03のいずれかを用いた場合におい て、 高精度の温度補償機能を持つフアブリペロー共振器を持つ波長モニタを実現 することができる。 According to the present invention, aligns the polarization of the laser beam to the extraordinary optical axis, and as a uniaxial birefringent crystal, α- BBO, j3 _BBO, when using any of L i I 0 3 Te odor, high A wavelength monitor having a Fabry-Perot resonator with an accurate temperature compensation function can be realized.
つぎの発明は、 上記の常光軸にレーザ光の偏光を揃える発明の場合において、 前記フアブリペロー共振器を構成する一軸性複屈折結晶を、 α— ΒΒΟ、 β-Β BO、 L i Ι 03、 C a C03のいずれかとし、 α— BBOの場合は、 光学軸の 光軸に対する角度を 76. 9 5度とし、 j8— BBOの場合は、 光学軸の光軸に対 する角度を 5 7. 05度とし、 L i I O 3の場合は、 光学軸の光軸に対する角度 を 1 8. 6 5度とし、 C a CO 3の場合は、 光学軸の光軸に対する角度を 6 7 · 5 度とすることを特徴とする。 Next invention, in the case of the invention for aligning the polarization of the laser beam to the normal light axis, a uniaxial birefringent crystal constituting the Fuaburipero resonator, α- ΒΒΟ, β-Β BO , L i Ι 0 3, and C a C0 3 either, alpha-case of BBO, and angle 76.9 5 degrees with respect to the optical axis of the optical axis, J8- for BBO, angle 5 7 against the optical axis of the optical axis . and 05 degrees, in the case of L i IO 3, and the angle a 1 8.6 5 degrees with respect to the optical axis of the optical axis, in the case of C a CO 3, the angle with respect to the optical axis of the optical axis 6 7.5 ° It is characterized by the following.
この発明によれば、 常光軸にレーザ光の偏光を揃え、 また、 一軸性複屈折結晶 として、 α— ΒΒΟ、 /3— BBO、 L i I 03、 C a C O 3のいずれかを用いた 場合において、 高精度の温度補償機能を持つフアブリペロー共振器を持つ波長モ ニタを実現することができる。 According to the present invention, aligns the polarization of the laser beam on the ordinary axis and as uniaxial birefringent crystal, alpha - used ΒΒΟ, / 3- BBO, one of L i I 0 3, C a CO 3 In this case, a wavelength monitor having a Fabry-Perot resonator having a high-precision temperature compensation function can be realized.
つぎの発明は、 上記の発明において、 前記フアブリペロー共振器を構成する一 軸性複屈折結晶は、 光学軸の光軸に対する設定角度を維持しつつ、 その光軸方向 の厚みを変化させることで、 温度補償条件を満足させてかつ波長弁別領域を調節 可能であることを特徴とする。 The following invention is the above-mentioned invention, wherein one component constituting the Fabry-Perot resonator is Axial birefringent crystals can satisfy the temperature compensation condition and adjust the wavelength discrimination region by changing the thickness in the direction of the optical axis while maintaining the set angle of the optical axis with respect to the optical axis. Features.
この発明 よれば、 温度補償条件が一軸性複屈折結晶の厚みに依存しないので、 温度調整条件を満たす任意の波長弁別領域を有するフアブリぺロ一共振器を得る ことが可能である。  According to the present invention, since the temperature compensation condition does not depend on the thickness of the uniaxial birefringent crystal, it is possible to obtain a Fabry-Perot resonator having an arbitrary wavelength discrimination region satisfying the temperature adjustment condition.
つぎの発明は、 上記の発明において、 前記半導体レーザから出射されるレーザ 光のビームサイズを調節し、 調節された光信号を上記フ了ブリペロー共振器に出 力する^ンズを備えることを特徴とする。  The next invention is characterized in that in the above invention, there is provided a lens for adjusting a beam size of a laser beam emitted from the semiconductor laser, and outputting the adjusted optical signal to the Fry-Bri-Perot resonator. I do.
この発明によれば、 レーザ光のビームサイズを調節してフアブリペロー共振器 に入射することが可能となる。  According to the present invention, it is possible to adjust the beam size of the laser beam and make it incident on the Fabry-Perot resonator.
つぎの発明は、 上記の発明において、 前記波長検出手段は、 前記フアブリぺロ 一共振器の透過光を検出する第 1の光検出器と、 前記半導体レーザから出力され るレーザ光を直接検出する第 2の光検出器と、 上記第 1および第 2の光検出器の 検出信号の比を用いて前記レーザ光の発振波長を検出する波長検出部とを備える ことを特 ί敷とする。  In the following invention, in the above invention, the wavelength detecting means directly detects a laser beam output from the semiconductor laser, and a first photodetector for detecting light transmitted through the Fabry-Perot resonator. It is characterized by comprising a second photodetector, and a wavelength detection unit that detects the oscillation wavelength of the laser light using the ratio of the detection signals of the first and second photodetectors.
この発明によれば、 第 1および第 2の光検出器の検出信号の比を用いて前記レ 一ザ光の—発振波長を検出するようにしているので、 半導体レーザの出力強度変化 に影響されることなく発振波長を正確に検出することができる。  According to the present invention, since the oscillation wavelength of the laser light is detected using the ratio of the detection signals of the first and second photodetectors, it is affected by the change in the output intensity of the semiconductor laser. It is possible to accurately detect the oscillation wavelength without the need.
つぎの発明は、 上記の発明において、 前記半導体レーザおよびフアブリペロー 共振器を載置するとともに、 前記第 2の光検出器が第 1の光検出器より上方に位 置するように前記第 1および第 2の光検出器を設置するベースキヤリァを更に備 え、 前記ベースキャリァ上に載置されたフアプリぺロ一共振器を透過したレーザ 光が前記第 2の光検出器で受光されないようにフアブリべ口一共振器の高さを調 節していることを特徴とする。  In the following invention, in the above invention, the semiconductor laser and the Fabry-Perot resonator are mounted, and the first and the second light detectors are positioned so that the second photodetector is located above the first photodetector. A base carrier on which the second photodetector is installed; and a fiber port for preventing the laser light transmitted through the ferromagnetic resonator mounted on the base carrier from being received by the second photodetector. The height of one resonator is adjusted.
この発明によれば、 フアブリべ口一共振器を透過したレーザ光が第 2の光検出 器で受光されることがなくなり、 発振波長を正確に検出することができる。 つぎの発明は、 上記の発明において、 前記半導体レーザおょぴフアブリペロー 共振器を載置するとともに、 前記第 2の光検出器が第 1の光検出器より上方に位 置するように前記第 1および第 2の光検出器を設置するベースキヤリァを更に備 え、 前記ベースキヤリァ上に載置されたフアブリべ口一共振器を透過したレーザ 光が前記第 2の光検出器で受光されることがないように前記第 2の光検出器を第 1の光検出器よりもフアブリべ口一共振器側に接近させて配置していることを特 徴とする。 According to the present invention, the laser light transmitted through the Fabry-Bale-One resonator is not received by the second photodetector, and the oscillation wavelength can be accurately detected. The next invention is the above invention, wherein the semiconductor laser and the Fabry-Perot resonator are mounted, and the first photodetector is positioned above the first photodetector. And a base carrier on which a second photodetector is installed, wherein the laser light transmitted through the Fabry-Body resonator mounted on the base carrier is not received by the second photodetector. As described above, the second photodetector is characterized in that it is disposed closer to the one side of the fabric port than the first photodetector.
この発明によれば、 フアブリペロー共振器を透過したレーザ光が第 2の光検出 器で受ぅ されることがなくなり、 発振波長を正確に検出することができる。  According to the present invention, the laser light transmitted through the Fabry-Perot resonator is not received by the second photodetector, and the oscillation wavelength can be accurately detected.
つぎの発明は、 半導体レーザから出力されるレーザ光の波長をモニタする波長 モニタ装置にぉレ、て、 前記レーザ光の光軸に垂直な面に対して光学軸が所定角度 傾くように切り出された一軸性複屈折結晶から成り、 前記レーザ光が入射する面 と出射する面とに光を反射する光反射膜を有し、 上記レーザ光の波長に応じて異 なる透過強度を有する透過光を出力する狭帯域用の第 1のフアブリペロー共振器 と、 前記第 1のフアブリペロー共振器に並設され、 前記レーザ光の光軸に垂直な 面に対して光学軸が所定角度傾くように切り出された一軸性複屈折結晶から成り、 前記レーザ光が入射する面と出射する面とに光を反射する光反射膜を有し、 上記 レーザ光の波長に応じて異なる透過強度を有する透過光を出力する広帯域用の第 2のフアブリペロー共振器と、 前記第 1およぴ第 2のフアブリペロー共振器の透 過光に基づきレーザ光の発振波長を測定する波長検出手段とを備えたことを特徴 とする。  The next invention is directed to a wavelength monitoring device that monitors the wavelength of laser light output from a semiconductor laser, and is cut out so that the optical axis is inclined at a predetermined angle with respect to a plane perpendicular to the optical axis of the laser light. And a light reflecting film that reflects light on a surface on which the laser light is incident and a surface on which the laser light is emitted, and transmits transmitted light having a different transmission intensity according to the wavelength of the laser light. A first Fabry-Perot resonator for a narrow band to be output, and a first Fabry-Perot resonator arranged in parallel with the first Fabry-Perot resonator, wherein the optical axis is cut out at a predetermined angle with respect to a plane perpendicular to the optical axis of the laser beam. It is made of a uniaxial birefringent crystal, has a light reflection film that reflects light on a surface on which the laser light is incident and on a surface on which the laser light is emitted, and outputs transmitted light having different transmission intensity according to the wavelength of the laser light Second broadband And Perot resonator, characterized in that a wavelength detection means for measuring the oscillation wavelength of the first Oyopi laser beam based on transparently light of the second Fuaburipero resonator.
この発明によれば、 一材料の一軸性複屈折結晶を用いて、 温度変化に応じて共 振器長の変化しないフアブリペロー共振器を構成することができるので、 構成が 単純ィ匕され、 波長モニタとしての信頼性が向上するとともに、 生産時に面倒な調 整作業を行わなくてもよくなり、 大量生産を実現することができる。 さらに、 こ の発明では、 狭帯域用およぴ広帯域用の 2つのフアブリぺロ一共振器を用レ、てレ 一ザ光の発振波長のモニタリングを行っているので、 極めて正確に発振波長を検 出することが可能となる。 According to the present invention, a Fabry-Perot resonator whose resonator length does not change in response to a temperature change can be configured by using a uniaxial birefringent crystal of one material, so that the configuration is simplified and a wavelength monitor is provided. As a result, it is possible to realize mass production without having to perform troublesome adjustment work during production. Furthermore, in the present invention, the laser wavelength is monitored using two fiber resonators for the narrow band and the wide band, so that the oscillation wavelength can be extremely accurately determined. Inspection Can be issued.
つぎの発明は、 上記の発明において、 前記半導体レーザから出力されるレーザ 光は、 一方向に偏光されたものであり、 上記第 1およぴ第 2のフアブリペロー共 振器を構成する一軸性複屈折結晶は、 前記レーザ光の光軸と偏光方向とで作られ る平面に対し平行な面内に光学軸があり、 この光学軸がレーザ光の光軸に対し所 定の角度傾いていることを特徴とする。  In the following invention, in the above invention, the laser beam output from the semiconductor laser is polarized in one direction, and the uniaxial laser constituting the first and second Fabry-Perot resonators is provided. The refractive crystal has an optical axis in a plane parallel to a plane formed by the optical axis of the laser light and the polarization direction, and the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser light. It is characterized by.
この発明によれば、 異常光軸にレーザ光の偏光を揃えており、 一お-料の一軸性 複屈折結晶を用いて、 温度補償機能を持つ 2つのフアブリぺロ一共振器を持つ波 長モニ を実現することができる。  According to the present invention, the polarization of the laser light is aligned with the extraordinary optical axis, and a wavelength having two Fabry-Perot resonators having a temperature compensation function using a uniaxial birefringent crystal is provided. Monies can be realized.
つぎの発明は、 上記の発明において、 前記半導体レーザから出力されるレーザ 光は、 一方向に偏光されたものであり、 上記フアブリペロー共振器を構成する一 軸性複屈折結晶は、 前記レーザ光の光軸と偏光方向とで作られる平面に対し垂直 な面内に光学軸があり、 この光学軸がレーザ光の光軸に対し所定の角度傾いてい ることを特徴とする。  In the following invention, in the above invention, the laser light output from the semiconductor laser is polarized in one direction, and the uniaxial birefringent crystal forming the Fabry-Perot resonator is The optical axis is in a plane perpendicular to a plane formed by the optical axis and the polarization direction, and the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser beam.
この発明によれば、 常光軸にレーザ光の偏光を揃えており、 一材料の一軸性複 ia折結晶を用いて、 温度補償機能を持つ 2つのフアブリペロー共振器を持つ波長 モニタを実現することができる。  According to the present invention, it is possible to realize a wavelength monitor having two Fabry-Perot resonators having a temperature compensating function by using a uniaxial biaxially-folded crystal of one material in which the polarization of laser light is aligned with the ordinary optical axis. it can.
つぎの—発明は、 上記の発明において、 広帯域用の第 2のフアブリペロー共振器 の波長弁別領域が半導体レーザの波長可変領域より大きく、 狭帯域用の第 1のフ アブリべ口一共振器の波長弁別領域が第 1のフアブリべ口一共振器の波長可変領 域に比べて十分小さくなるように、 第 1および第 2のフアブリペロー共振器を構 成する一軸性複屈折結晶の光軸方向の厚みを設定することを特徴とする。  The following invention is the invention according to the above invention, wherein the wavelength discrimination region of the second Fabry-Perot resonator for a wide band is larger than the wavelength variable region of the semiconductor laser, and the wavelength of the first Fabry-Perot resonator for a narrow band is The thickness in the optical axis direction of the uniaxial birefringent crystal constituting the first and second Fabry-Perot resonators so that the discrimination area is sufficiently smaller than the wavelength variable area of the first Fabry-Perot resonator. Is set.
この発明によれば、 一軸性複屈折結晶の光軸方向の厚み設定により狭帯域用お よぴ広帯域用の 2つのフアブリペロー共振器を構成するようにしており、 簡便に 狭帯域用おょぴ広帯域用の 2つのフアブリペロー共振器を実現することが可能と なる。  According to the present invention, by setting the thickness of the uniaxial birefringent crystal in the optical axis direction, two Fabry-Perot resonators for a narrow band and for a wide band are configured, so that a narrow band for a narrow band is easily provided. Two Fabry-Perot resonators can be realized.
つぎの発明は、 上記の発明において、 前記波長検出手段は、 前記第 1のフアブ リペロー共振器の透過光を検出する第 1の光検出器と、 前記半導体レーザから出 力されるレーザ光を直接検出する第 2の光検出器と、 前記第 2のフアブリペロー 共振器の透過光を検出する第 3の光検出器と、 上記第 1およぴ第 2の光検出器の 検出信号の比おょぴ前記第 3および第 2の光検出器の検出信号の比を用いて前記 レーザ光の発振波長を検出する波長検出部とを備えることを特徴とする。 In the following invention, in the above invention, the wavelength detecting means is a first fiber. A first photodetector for detecting the transmitted light of the Reperot resonator, a second photodetector for directly detecting the laser light output from the semiconductor laser, and a transmitted light of the second Fabry-Perot resonator. A third photodetector to be detected, and a ratio of detection signals of the first and second photodetectors, and a ratio of the detection signals of the third and second photodetectors to the laser. A wavelength detector for detecting an oscillation wavelength of light.
この発明によれば、 第 1およぴ第 2の光検出器の検出信号の比と、 第 3および 第 2の光検出器の検出信号の比とを用いて前記レーザ光の発振波長を検出するよ うにしているので、 半導体レーザの出力強度変化に影響されることなく発振波長 を極めで正確に検出することができる。  According to this invention, the oscillation wavelength of the laser light is detected using the ratio of the detection signals of the first and second photodetectors and the ratio of the detection signals of the third and second photodetectors. As a result, the oscillation wavelength can be extremely accurately detected without being affected by a change in the output intensity of the semiconductor laser.
つぎの発明は、 上記の発明において、 前記半導体レーザおょぴフアブリペロー 共振器を載置するとともに、 前記第 2および第 3の光検出器が第 1の光検出器よ り上方に位置するように前記第 1〜第 3の光検出器を設置するベースキヤリアを 更に備え、 前記ベースキャリア上に載置されたフアプリペロー共振器を透過した レーザ光が前記第 2およぴ第 3の光検出器で受光されないように前記第 2および 第 3の光検出器を第 1の光検出器よりもフアブリペロー共振器側に接近させて配 置していることを特徴とする。  The next invention is the above invention, in which the semiconductor laser and the Fabry-Perot resonator are mounted, and the second and third photodetectors are positioned above the first photodetector. A base carrier on which the first to third photodetectors are installed, wherein the laser light transmitted through the resonator of the resonator mounted on the base carrier is received by the second and third photodetectors; The second and third photodetectors are arranged closer to the Fabry-Perot resonator side than the first photodetector so as not to be performed.
この発明によれば、 フアブリべ口一共振器を透過したレーザ光が第 2およぴ第 3の光検出器で受光されることがなくなり、 発振波長を正確に検出することがで さる。 図面の簡単な説明  According to this invention, the laser light transmitted through the Fabry-Bale-One resonator is not received by the second and third photodetectors, and the oscillation wavelength can be accurately detected. BRIEF DESCRIPTION OF THE FIGURES
第 1図は従来の波長モニタ装置の構成図であり、 第 2図は従来のファブリぺ ロー共振器を示す斜視図であり、 第 3図は実施の形態 1における波長モニタ装置 の構成図であり、 第 4図はフアブリペロー共振器の波長に対する透過率の変化を 示すグラフであり、 第 5図は一軸性複屈折結晶を用いたフアブリペロー共振器を 表す構成図であり、 第 6図は 3 - B B〇結晶の物性値を示す図であり、 第 7図は /3 -B B O結晶の d ii / d T + a nの温度 Tに対する依存性を示すグラフであり - 第 8図は |8 _B B O結晶の線膨張率 aの C軸-光軸間角度 φ cに対する依存性を示 すグラフであり、 第 9図は J3 - B B O結晶の異常光屈折率 ηの C軸-光軸間角度 φ cに対する依存性を示すグラフであり、 第 1 0図は /3 - Β Β〇結晶の異常光屈折 率の温度に対する変化 d n/ d Τの C軸-光軸間角度 <i> cに対する依存性を示すグ ラフであり、 第 1 1図は L i I 0 3結晶の d n / d T+ a nの温度 Tに対する依存 性を示すグラフであり、 第 1 2図は実施の形態 1における波長制御装置を表す構 成図であり、 第 1 3図は実施の形態 1の波長モニタ装置の変更態様を示す構成図 であり、 第 1 4図は実施の形態 2 iこおける波長モニタ装置の構成図であり、 第 1 5図は 施の形態 2における波長制御装置の構成図であり、 第 1 6図は、 狭帯域 用のフアブリぺロ一共振器および広帯域用のフアブリぺロ一共振器のそれぞれの 波長透過特性を示すグラフであり、 第 1 7図は実施の形態 2の波長モニタ装置の 変更態様を表す構成図である。 発明を実施するための最良の形態 FIG. 1 is a configuration diagram of a conventional wavelength monitoring device, FIG. 2 is a perspective view showing a conventional Fabry-Perot resonator, and FIG. 3 is a configuration diagram of a wavelength monitoring device in the first embodiment. FIG. 4 is a graph showing a change in transmittance with respect to wavelength of a Fabry-Perot resonator, FIG. 5 is a configuration diagram showing a Fabry-Perot resonator using a uniaxial birefringent crystal, and FIG. 6 is a diagram showing a 3-BB FIG. 7 is a graph showing the physical property values of the crystal, and FIG. 7 is a graph showing the dependence of d ii / d T + an on the temperature T of the / 3-BBO crystal. Figure 8 is a graph showing the dependence of the linear expansion coefficient a of the | 8 _B BO crystal on the angle c between the C-axis and the optical axis. Figure 9 shows the C3 of the extraordinary light refractive index η of the J3-BBO crystal. Fig. 10 shows the dependence of the extraordinary refractive index of the crystal on the temperature dn / d Τ between the C-axis and the optical axis. a graph showing the dependency on <i> c, the first 1 Figure is a graph showing the dependence on the temperature T of the L i I 0 3 crystals of dn / d T + an, first Fig. 2 embodiment FIG. 13 is a configuration diagram illustrating a wavelength control device according to Embodiment 1, FIG. 13 is a configuration diagram illustrating a modification of the wavelength monitor device according to Embodiment 1, and FIG. 14 is a wavelength diagram according to Embodiment 2 i. FIG. 15 is a configuration diagram of a monitor device, FIG. 15 is a configuration diagram of a wavelength control device according to the second embodiment, and FIG. 16 is a configuration diagram of a narrow-band Fabry-Perot resonator and a broadband filter. Ripero is a graph showing the respective wavelength transmission characteristics one resonator, the first FIG. 7 is a block diagram showing a modification of the wavelength monitor device according to the second embodiment. BEST MODE FOR CARRYING OUT THE INVENTION
以下に添付図面を参照して、 この発明にかかる波長モニタ装置の好適な実施の 形態を詳細に説明する。  Hereinafter, preferred embodiments of a wavelength monitor device according to the present invention will be described in detail with reference to the accompanying drawings.
実施の形態 1 . Embodiment 1
第 3図はこの発明の実施の形態 1による波長モニタ装置 （あるいは波長安定化 光源） を示す構成図である。 半導体レーザ 1は一方向に偏光したレーザ光 （以下 光信号と称する） を出射する。 半導体レーザ 1としては、 例えば、 活性層中に回 折格子を有する分布帰還型 (DFB)レーザ、 注入電流または温度によって波長を変 えることができる波長可変レーザダイォード、 または電界吸収素子とレーザダイ オードとを直列に配置した複合型 (EA/LD)モジュールなどを採用する。 また、 半 導体レーザ 1は、 第 1 2図に示されている波長制御装置から入力される制御信号 T 1によって注入電流または温度等が変化し、 波長が制御される。  FIG. 3 is a configuration diagram showing a wavelength monitor (or a wavelength stabilized light source) according to Embodiment 1 of the present invention. The semiconductor laser 1 emits laser light (hereinafter referred to as an optical signal) polarized in one direction. Examples of the semiconductor laser 1 include a distributed feedback (DFB) laser having a diffraction grating in an active layer, a tunable laser diode whose wavelength can be changed by injection current or temperature, or an electroabsorption element and a laser diode. And a compound type (EA / LD) module in which the components are arranged in series. Further, the injection current or the temperature of the semiconductor laser 1 is changed by the control signal T1 input from the wavelength control device shown in FIG. 12, and the wavelength is controlled.
半導体レーザ 1から出射される光信号は、 レンズ 2によって集光され、 平行光 として出力される。 このレンズ 2によって、 光信号のビームサイズを調整して フアプリペロー共振器 3に入射する。 半導体レーザ 1の出射面中心とレンズ 2の 中心とを結ぶ軸が光軸となる。 本実施の形態 1および後述する実施の形態 2では、 光信号の進行方向（光軸方向）を空間座標において Z軸の方向と定め、 空間におけ る上方向を Y軸の方向と定め、 Z軸および Y軸に直交する方向（第 3図において 紙面に垂直で、 手前に向かう方向）を X軸と定める。 半導体レーザ 1から出射さ れる光信号は X軸方向に振動する偏光成分を有するものとする。 An optical signal emitted from the semiconductor laser 1 is condensed by the lens 2 and output as parallel light. This lens 2 adjusts the beam size of the optical signal The incident light enters the resonator 3. The axis connecting the center of the emission surface of the semiconductor laser 1 and the center of the lens 2 is the optical axis. In Embodiment 1 and Embodiment 2 to be described later, the traveling direction (optical axis direction) of an optical signal is defined as the Z-axis direction in space coordinates, and the upward direction in space is defined as the Y-axis direction. The direction perpendicular to the axis and the Y axis (in Fig. 3, perpendicular to the plane of the paper and facing forward) is defined as the X axis. It is assumed that the optical signal emitted from the semiconductor laser 1 has a polarization component that vibrates in the X-axis direction.
フアプリべ口一共振器 3は、 半導体レーザ 1からの光信号が入射する入射面と 出射する出射面とに光を反射する反射膜 7および 8を有し、 その材料としては、 —種類 一材料） の一軸性複屈折結晶のみ (例えば、 ]3 - B B O結晶、 α - B B O 結晶、 L i I 0 3結晶、 C a C〇3結晶などのいずれ力 で形成されている。 ファ ブリペロー共振器 3の材料として用いられる一軸性複屈折結晶の結晶切り出し面 は光軸に直交する XY面に平行になるように配置され、 一軸性複屈折結晶の光学 軸（以下、 C軸と称する） は、 レーザ光の光軸に垂直な X Y面に対して所定角度 傾斜されている。 The resonator 3 has reflecting films 7 and 8 for reflecting light on an incident surface on which an optical signal from the semiconductor laser 1 is incident and on an emitting surface on which the optical signal is emitted. uniaxial birefringent crystal only) (e.g.,] 3 - BBO crystal, alpha -. BBO crystal, L i I 0 3 crystal, C a C_〇 3 are formed by any force such as crystalline files Buripero resonator 3 The cut-out plane of the uniaxial birefringent crystal used as the material for the crystal is arranged so as to be parallel to the XY plane orthogonal to the optical axis, and the optical axis of the uniaxial birefringent crystal (hereinafter referred to as the C axis) is a laser. It is inclined at a predetermined angle with respect to the XY plane perpendicular to the optical axis of light.
第 1のフォトダイオード （主光検出器） 4は、 フアブリペロー共振器 3を透過 した光信号を受光しその強度 (光電流値）を検出し、 光強度モニタ信号 S 1を出力 する。  The first photodiode (main photodetector) 4 receives the optical signal transmitted through the Fabry-Perot resonator 3, detects its intensity (photocurrent value), and outputs a light intensity monitor signal S1.
第 2の—フォトダイォード （副光検出器） 5は、 第 1のフォトダイオード 4の上 方に配置され、 フアブリべ口一共振器 3を透過せず半導体レーザ 1から出射され る光信号を直接に受光しその強度 (光電流値)を検出し、 光強度モニタ信号 S 2を 出力する。  The second—photodiode (sub-photodetector) 5 is disposed above the first photodiode 4, and converts an optical signal emitted from the semiconductor laser 1 without passing through the cavity 3 and the resonator 3. It directly receives light, detects its intensity (photocurrent value), and outputs a light intensity monitor signal S2.
これら半導体レーザ 1、 レンズ 2、 フアブリペロー共振器 3、 第 1のフォトダ ィオード 4およぴ第 2のフォトダイオード 5は、 ベースキャリア 6上に設置され ている。 なお、 フアブリペロー共振器 3を透過した光信号が第 2のフォトダイォ ード 5で受光されることがないように、 フアブリペロー共振器 3の高さ、 あるい は第 2のフォトダイォード 5の設置高さが調整されている。  These semiconductor laser 1, lens 2, Fabry-Perot resonator 3, first photodiode 4, and second photodiode 5 are mounted on base carrier 6. The height of the Fabry-Perot resonator 3 or the height of the second photodiode 5 is set so that the optical signal transmitted through the Fabry-Perot resonator 3 is not received by the second photodiode 5. Has been adjusted.
ここで、 フアブリペロー共振器 3を透過した光信号の波長に対する透過特性は、 温度変化に関係なく一定に保たれる。 つまり、 フアプリペロー共振器 3は温度補 償機能を有する。 次に、 フアブリペロー共振器 3の温度補償条件を説明する。 第 3図に示す波長モニタ装置においては、 長方形状のフアブリべ口一共振器 3 の入射面に光信号が垂直に入射している。 フアプリペロー共振器 3は入射および 出射面に反射膜 7および 8を有し、 その強度反射率を Rとすると、 フアブリぺロ 一共振器 3を透過した光信号強度の波長に対する依存性は式 （ 3 ) および第 4図 で表される。 TR (λ) は透過率である。 Here, the transmission characteristics with respect to the wavelength of the optical signal transmitted through the Fabry-Perot resonator 3 are as follows: It is kept constant regardless of temperature changes. In other words, the Flipper Perot resonator 3 has a temperature compensation function. Next, the temperature compensation condition of the Fabry-Perot resonator 3 will be described. In the wavelength monitor device shown in FIG. 3, an optical signal is vertically incident on the incident surface of a rectangular Fabry-Bore-One resonator 3. Assuming that the intensity reflectance is R, the dependence of the intensity of the optical signal transmitted through the Fabry-Perot resonator 3 on the wavelength with respect to the wavelength is given by: ) And Figure 4. TR (λ) is the transmittance.
(1-R) (1-R)
(3)  (3)
兀 riJL、  Vat riJL,
(1-R)' +4Rsin' (^- ^  (1-R) '+ 4Rsin' (^-^
λ この場合、 フアブリペロー共振器 3を透過した光信号の強度は光信号の周波数 に対して周期的な変化を示す。 この 1周期分に対応する周波数間隔を、 フアブリ ペロー共振器 3を透過した光信号の波長に対するフリースぺク トルレンジ (以下 FSRと称する、 自由スペク トル間隔） という。 FSRは、 光軸方向の共振器長、 第 3図の場合にぉレ、ては一軸性複屈折結晶 3の Ζ軸方向の長さ Lおよぴ屈折率 η に依存し、 次の式 （4) で表される。 cは光速である。  λ In this case, the intensity of the optical signal transmitted through the Fabry-Perot resonator 3 changes periodically with respect to the frequency of the optical signal. The frequency interval corresponding to one cycle is called a free spectral range (hereinafter, referred to as FSR, free spectral interval) with respect to the wavelength of the optical signal transmitted through the Fabry-Perot resonator 3. The FSR depends on the length of the resonator in the direction of the optical axis, the length in the case of FIG. 3, and the length L and the refractive index η of the uniaxial birefringent crystal 3 in the Ζ-axis direction. 4) c is the speed of light.
FSR: (4) FSR: (4)
2nL フアブリペロー共振器 3を透過した光信号強度の波長に対する依存性が温度に よつて変化しないということが、 フアブリべ口一共振器に対する温度捕償条件で ある。 したがって、 温度補償を可能にするためには、 式 （4) で表される FSR が温度に依存しないことが必要である。 F SRが温度 Tに対して一定であるため には、 式 （4) において共振器長 n Lが温度 Tに対して一定の値を持つというこ とが必要である。 この関係を表したものが式 （5) である。 W The temperature compensating condition for a Fabry-Perot single resonator is that the dependence of the intensity of the optical signal transmitted through the 2nL Fabry-Perot resonator 3 on the wavelength does not change with temperature. Therefore, to enable temperature compensation, it is necessary that the FSR expressed by equation (4) does not depend on temperature. In order for FSR to be constant with respect to temperature T, it is necessary in equation (4) that the resonator length n L has a constant value with respect to temperature T. Equation (5) expresses this relationship. W
13 13
9 - T dn T 5L 9- T dn T 5L
— (nL) =— L + n—： 0 (5)  — (NL) = — L + n—: 0 (5)
5T δΤ フアブリぺロ一共振器 3の光軸方向（第 3図における Z方向）の線膨張率を と すると、 フアブリペロー共振器 3の物理長 Lは式 （6 ) で表される。  Assuming that the linear expansion coefficient in the optical axis direction (Z direction in FIG. 3) of the 5T δΤ Fabry-Perot resonator 3 is, the physical length L of the Fabry-Perot resonator 3 is expressed by the following equation (6).
L = L0 OL + a; T) · · -(6) ここで、 L。は 0 °Cにおけるフアブリべ口一共振器の Z軸方向の物理長である。 式 （5 ) を式 （6 ) に代入すると、 フアブリペロー共振器 3の温度捕償条件は式 ( 7 ) となる。 L = L 0 OL + a; T) · ·-(6) where L. Is the physical length in the Z-axis direction of the Fabry-Berke-One resonator at 0 ° C. Substituting equation (5) into equation (6), the temperature compensation condition of the Fabry-Perot resonator 3 becomes equation (7).
— + n a = 0 · · · (7) — + N a = 0 · · · (7)
5T ' フアブリペロー共振器 3の材料として、 一つの C軸を有する一軸性複屈折結晶 を用レ、た場合における入射した光信号の光軸と C軸との位置関係と、 フアブリべ ロー共振器 3の線膨張率および屈折率について説明する。- なお、 レーザ光の偏光方向 （この場合 X方向） を一軸性複屈折結晶の異常光軸 あるいは常光軸に揃えた場合でも、 温度補償条件を満足させることができるが、 以下の説明では、 レーザ光の偏光方向を一軸性複屈折結晶の異常光軸に揃えた場 合について説明する。  5T ′ A uniaxial birefringent crystal having one C-axis is used as the material of the Fabry-Perot resonator 3, and the positional relationship between the optical axis of the incident optical signal and the C-axis when the Fabry-Perot resonator 3 is used. The linear expansion coefficient and the refractive index will be described. -The temperature compensation condition can be satisfied even when the polarization direction of the laser beam (in this case, the X direction) is aligned with the extraordinary or ordinary optical axis of the uniaxial birefringent crystal. A case where the polarization direction of light is aligned with the extraordinary optical axis of a uniaxial birefringent crystal will be described.
第 5図において、 フアブリぺロ一共振器の材料である一軸性複屈折結晶の C軸 は X Z平面内にあり、 光軸は Z軸に対して平行であり、 C軸は光軸に対して一定 の角度 Φ c傾いている。 またフアブリペロー共振器 3に入射する光信号の偏光は フアプリペロー共振器 3に対して p偏光であり、 第 3図においては X方向に対応 している。 異常光線は、 C軸と光軸方向によって作られる面と同じ振動面をもつ ので、 この場合、 入射した光信号はフアブリぺロ一共振器 3内を異常光線として 伝播することがわる。 異常光線に対 "る屈折率 nは、 光軸と C軸とのなす角 に依存し、 neおよび noは温度 Tに依存することから、 n(^c， T)で表し、 式 (8) のようになる。 In FIG. 5, the C axis of the uniaxial birefringent crystal, which is the material of the Fabry-Perot resonator, is in the XZ plane, the optical axis is parallel to the Z axis, and the C axis is relative to the optical axis. A certain angle Φ c is inclined. The polarization of the optical signal incident on the Fabry-Perot resonator 3 is p-polarized with respect to the Fabry-Perot resonator 3 , and corresponds to the X direction in FIG. The extraordinary ray has the same oscillating plane as the plane created by the C axis and the optical axis direction Therefore, in this case, the incident optical signal propagates as an extraordinary ray in the Fabry-Perot resonator 3. The refractive index n for an extraordinary ray depends on the angle between the optical axis and the C axis, and ne and no depend on the temperature T. Therefore, they are expressed as n (^ c, T). become that way.
η(φο,Τ) · - - (8)η (φο, Τ)---(8)
Figure imgf000016_0001
ここで、 ne は C軸と平行な方向の偏光成分に対する屈折率 （異常光屈折率） であり、 no は C軸と垂直な方向の偏光成分に対する屈折率 （常光屈折率） であ る。 また η (φο， Τ)は、 一軸性複屈折結晶を材料とするフアブリペロー共振器 に入射する光信号に対する屈折率である。
Figure imgf000016_0001
Here, ne is the refractive index for the polarized light component in the direction parallel to the C axis (the extraordinary light refractive index), and no is the refractive index for the polarized light component in the direction perpendicular to the C axis (the ordinary light refractive index). Η (φο, Τ) is the refractive index for an optical signal incident on a Fabry-Perot resonator made of a uniaxial birefringent crystal.
—軸性複屈折結晶の光軸方向における線膨張率 αは式 （9) のように表される。 ac は C軸に平行な方向の線膨張係数、 aa は C軸に垂直な方向の線膨張係数で ある。  —The linear expansion coefficient α of the axially birefringent crystal in the direction of the optical axis is expressed by equation (9). ac is the coefficient of linear expansion in the direction parallel to the C axis, and aa is the coefficient of linear expansion in the direction perpendicular to the C axis.
- a = c cos φε + αΛ sin— 0 · · · (9) 本出願における発明者たちは、 フアブリペロー共振器の材料として検討を行つ た一軸性複屈折結晶について、 C軸の光軸に対する傾き φ cの値を変化させるこ とにより、 式 （7) を満たす一軸性複屈折結晶およびその場合の φ cの値を調べ た。 その結果、 J3- BBO(B a Β204)結晶、 α— ΒΒΟ結晶、 L i I 03、 C a C〇3などが式 （7) を満たすことを見出した。 これらの結晶は、 レーザ光の 波長変換素子として用いられている。 -a = c cos φ ε + α Λ sin — 0 · · · (9) The inventors of the present application have proposed a uniaxial birefringent crystal studied as a material for Fabry-Perot resonators, with the C-axis optical axis. By changing the value of the inclination φc with respect to, the uniaxial birefringent crystal satisfying the equation (7) and the value of φc in that case were investigated. As a result, J3- BBO (B a Β 2 0 4) crystals, such as alpha-Betabetaomikuron crystal, L i I 0 3, C a C_〇 3 is found to satisfy the equation (7). These crystals are used as wavelength conversion elements for laser light.
第6図に ]3— BBO結晶の諸特性を示す。 すなわち、 /3—BBOの異常光屈折 率 ne は 1. 53 1 1で、 常光屈折率 no は 1. 646 7で、 熱光学係数 d no/ dTは一 16. 8 X 10— 6/Kで、 熱光学係数 d ne/dTは _ 8. 8 X 10— 6/ で、 線膨張係数 ac は 33. 3X 10— 6/Kで、 線膨張係数 a a は 0 · 5 X 1 0一6/ Kである。 Fig. 6 shows the characteristics of] 3-BBO crystal. That is, the extraordinary refractive index ne of / 3—BBO is 1.531, the ordinary refractive index no is 1.6467, and the thermo-optic coefficient d no / dT in one 16. 8 X 10- 6 / K, the thermal-optic coefficient d ne / dT is _ 8. 8 X 10- 6 / a, coefficient of linear expansion ac is 33. 3X 10- 6 / K, the linear expansion The coefficient aa is 0 · 5 X 10 16 / K.
また、 第 7図に、 /3— BBOからなる一軸性複屈折結晶をフアブリペロー共振 器 3として用い、 力 レーザ光の偏光方向を異常光軸に揃えた場合における式 （ 7) に示した 3 η/3 Τ+η αと、 光軸と C軸となす角 ψ cとの関係を示すグラフ を示す。 第 8図は 一 BBO結晶での線膨張係数ひの角度 φ cに対する依存性を 示すグラフであり、 第 9図は 0— BBOの結晶での屈折率 nの角度 φ cに対する 依存性お示すダラフであり、 第 10図は j3— BBOの結日曰曰での d n / d Tの角度 φ cに対する依存性を示すグラフである。 すなわち、 第 8図の線膨張係数 αと角 度 cとの関係と、 第 9図の屈折率 ηと角度 φ cとの関係と、 第 10図の d n/ dTと角度 φ cとの関係とを用いて、 第 7図に示す 311/3 T+n aと角度 ψ cと の関係が得られる。  Also, FIG. 7 shows the case where a uniaxial birefringent crystal composed of / 3-BBO is used as the Fabry-Perot resonator 3 and the polarization direction of the force laser beam is aligned with the extraordinary optical axis, and 3η shown in equation (7). 3 is a graph showing the relationship between Τ + ηα and the angle ψc between the optical axis and the C axis. Fig. 8 is a graph showing the dependence of the coefficient of linear expansion on the angle φc in one BBO crystal. Fig. 9 is the graph showing the dependence of the refractive index n on the angle φc in a 0-BBO crystal. Fig. 10 is a graph showing the dependence of dn / dT on the angle φc as stated by j3- BBO. That is, the relationship between the linear expansion coefficient α and the angle c in FIG. 8, the relationship between the refractive index η and the angle φc in FIG. 9, the relationship between dn / dT and the angle φc in FIG. Is used to obtain the relationship between 311/3 T + na and the angle ψc shown in FIG.
第 7図で示したように、 一軸性複屈折結晶 BBOを用いた場合、 光軸と C 軸とのなす角 φ cを 64. 75度にすると、 3 η/3Τ+η α = 0となり、 温度補 償条件式 （7) が満足される。 例えば、 実施の形態 1に用いられている狭帯域用 の波長モニタ装置において、 FSRを、 レーザ光の波長変動幅 0. 8 nmに対応 する 10:0 GHz (1. 0 X 10 "Hz) と設定したいときには、 式 （4) お ょぴ式 (8) を用いて、 一軸性複屈折結晶 ]3- BBOの Z軸方向の厚み L=970 μ mを得る。 この厚み L = 970 mは十分実用的なサイズである。  As shown in Fig. 7, when the uniaxial birefringent crystal BBO is used, if the angle φc between the optical axis and the C axis is 64.75 degrees, then 3η / 3Τ + ηα = 0, The temperature compensation condition (7) is satisfied. For example, in the wavelength monitor for a narrow band used in the first embodiment, the FSR is set to 10: 0 GHz (1.0 × 10 "Hz) corresponding to a wavelength fluctuation width of 0.8 nm of laser light. When it is desired to set, using Equation (4) and Equation (8), the thickness L of the uniaxial birefringent crystal] 3-BBO in the Z-axis direction L = 970 μm is obtained. It is a practical size.
すなわち、 第 7図に示す 3 η/3Τ+η αと角度 ψ όとの関係から、 式 （7) を 満足する角度 φ ο:を求め、 この求めた角度 ψ cを用いて式 （8) に基づき屈折率 nを求め、 さらに求められた角度 φ cおよび屈折率 nを用いて式 （4) に基づき、 一軸性複屈折結晶 3の Z軸方向の長さ Lを調整して、 所望の F S Rを得るように する。 That is, from the relationship between 3 η / 3Τ + η α and the angle ψ 示 す shown in FIG. 7, an angle φ ο: that satisfies the equation (7) is obtained. The refractive index n is calculated based on the following formula, and the length L of the uniaxial birefringent crystal 3 in the Z-axis direction is adjusted based on the equation (4) using the obtained angle φ c and the refractive index n to obtain a desired value. Try to get FSR.
なお、 温度補償条件式 （7) は、 一軸性複屈折結晶をフアブリペロー共振器 3 として用いた場合、 一軸性複屈折結晶の Z軸方向の長さ Lには依存しないので. 式 （4 ) より温度補償条件を満たす任意の F S Rを持つフアブリペロー共振器を 作ることができる。 Note that the temperature compensation condition (7) does not depend on the length L of the uniaxial birefringent crystal in the Z-axis direction when the uniaxial birefringent crystal is used as the Fabry-Perot resonator 3. Equation (4) shows that a Fabry-Perot resonator with an arbitrary FSR that satisfies the temperature compensation condition can be made.
次に第 3図の波長モニタ装置の動作について説明する。 半導体レーザ 1から出 射された光信号はレンズ 2におレ、て集光される。 この集光された光信号の上方部 分は直接に第 2のフォトダイォード 5で受光される。 第 2のフォトダイォード 5 は受光した光信号の強度を検出しモニタする。 この強度モニタ信号 S 2と予め設 定された光信号強度との差に基づき出力制御回路 (図示省略)は、 半導体レーザ 1 の光出力を一定に制御する。  Next, the operation of the wavelength monitor of FIG. 3 will be described. The optical signal emitted from the semiconductor laser 1 is focused on the lens 2. The upper part of the collected optical signal is directly received by the second photodiode 5. The second photodiode 5 detects and monitors the intensity of the received optical signal. An output control circuit (not shown) controls the optical output of the semiconductor laser 1 to be constant based on the difference between the intensity monitor signal S2 and a preset optical signal intensity.
また、 レンズ 2において集光された光信号の下方部分は、 p偏光成分すなわち X軸方向へ振動している光信号であり、 光信号は )8— B B Oからなるフアブリべ ロー共振器 3を、 C軸と角度 ψ c = 6 4 . 7 5度をもって透過する。 - B B O等 の一屈折結晶を材料とするフアブリペロー共振器 3を透過する光信号の偏光方向 は、 一軸性複屈折結晶の異常光軸と平行であるため、 フアブリペロー共振器 3を 透過する際、 光信号の偏光は変わらず p偏光のまま保たれる。 フアブリペロー共 振器 3より出射した光信号の強度は式 （3.) のような波長弁別特性を持ち、 その 特性は結晶の温度変化に関係なく一定に保たれるので、 このフアブリペロー共振 器 3は温度補償機能を持つ。  The lower part of the optical signal condensed by the lens 2 is a p-polarized component, that is, an optical signal oscillating in the X-axis direction, and the optical signal is a Fabry-Bellows resonator 3 composed of) 8-BBO. Transmission with C axis and angle ψ c = 64.75 degrees. -Since the polarization direction of the optical signal passing through the Fabry-Perot resonator 3 made of a unirefringent crystal such as BBO is parallel to the extraordinary optical axis of the uniaxial birefringent crystal, The polarization of the signal remains p-polarized. The intensity of the optical signal emitted from the Fabry-Perot resonator 3 has a wavelength discrimination characteristic as shown in Equation (3.), and the characteristic is kept constant irrespective of the temperature change of the crystal. Has temperature compensation function.
第 1の オトダイォード 4はフアブリペロー共振器 3を通過した光信号の強度 を検出し、 光強度モニタ信号 S 1を出力する。 一方、 第 2のフォトダイオード 5 は、 前述したように、 半導体レーザ 1から出射される光信号強度を直接検出し、 光強度モニタ信号 S 2を出力する。 これら光強度モニタ信号 S 1、 S 2は第 1 2 図に示される波長制御装置 5 0へ送られる。 波長制御装置 5 0は、 光信号の波長 を検出し、 この検出波長があらかじめ設定された波長（たとえば第 4図における 基準波長え 0 )に一致するように、 半導体レーザ 1を制御する。  The first photodiode 4 detects the intensity of the optical signal passing through the Fabry-Perot resonator 3, and outputs an optical intensity monitor signal S1. On the other hand, the second photodiode 5 directly detects the optical signal intensity emitted from the semiconductor laser 1 and outputs the optical intensity monitor signal S2, as described above. These light intensity monitor signals S 1 and S 2 are sent to the wavelength controller 50 shown in FIG. The wavelength controller 50 detects the wavelength of the optical signal, and controls the semiconductor laser 1 such that the detected wavelength matches a preset wavelength (for example, the reference wavelength 0 in FIG. 4).
波長制御装置 5 0について説明する。 第 1 2図は波長制御装置 5 0の構成図で ある。 波長制御装置 5 0は、 波長検出部 5 1とレーザ制御部 5 2力 ら構成される。 波長検出部 5 1には、 第 1および第 2のフォトダイオードからの光強度モニタ信 号 S 1、 S 2と、 予め設定された基準波長; L 0が入力される。 波長検出部 5 1は、 光強度モニタ信号 S 1、 S 2によって半導体レーザ 1より出射されている光信号 の発振波長を求め、 この発振波長と基準波長 I 0との差を求める。 レーザ制御部 5 2には、 波長検出部 5 1から基準波長; L 0と半導体レーザ 1から出射された発 振波長との差が入力される。 レーザ制御部 5 2は、 その差に応じて発振波長が基 準波長 λ 0に一致するように半導体レーザ 1の温度や注入電流等を制御するため の制御信号 Τ 1を求め、 この制御信号 Τ 1を半導体レーザ 1に出力する。 The wavelength controller 50 will be described. FIG. 12 is a configuration diagram of the wavelength control device 50. The wavelength controller 50 includes a wavelength detector 51 and a laser controller 52. The wavelength detector 51 receives light intensity monitor signals from the first and second photodiodes. Signals S 1 and S 2 and a preset reference wavelength; L 0 are input. The wavelength detector 51 obtains the oscillation wavelength of the optical signal emitted from the semiconductor laser 1 based on the light intensity monitor signals S1 and S2, and obtains the difference between the oscillation wavelength and the reference wavelength I0. The difference between the reference wavelength; L 0 from the wavelength detector 51 and the oscillation wavelength emitted from the semiconductor laser 1 is input to the laser controller 52. The laser control unit 52 obtains a control signal Τ1 for controlling the temperature, injection current, and the like of the semiconductor laser 1 so that the oscillation wavelength coincides with the reference wavelength λ0 according to the difference. 1 is output to the semiconductor laser 1.
次に波長検出部 5 1の動作について詳細説明する。 フアブリペロー共振器 3の 波長に *Η "る透過率の関係が第 4図のように表されている。 第 4図における基準 波長; L 0に発振波長を合わせる場合について説明する。 第 4図によれば、 基準波 長え 0の近傍の波長領域で見ると、 第 1のフォトダイオード 4により検出される 光強度モニタ信号 S 1の値は、 光信号の波長が長波長側にずれると小さくなり、 短波長側にずれると大きくなるということが分かる。 この波長の変化に伴う光強 度モニタ信号 S 1の変化をモニタし、 基準波長; I 0からのずれを算出する。  Next, the operation of the wavelength detector 51 will be described in detail. The relationship between the transmittance and the wavelength of the Fabry-Perot resonator 3 is shown in Fig. 4. The case where the oscillation wavelength is adjusted to the reference wavelength; L0 in Fig. 4 will be described. According to this, when viewed in the wavelength region near the reference wavelength 0, the value of the light intensity monitor signal S 1 detected by the first photodiode 4 becomes smaller as the wavelength of the optical signal shifts to the longer wavelength side. It can be seen that the shift to the short wavelength side increases, and the change in the light intensity monitor signal S1 accompanying the change in the wavelength is monitored, and the shift from the reference wavelength;
次に、 基準波長; L 0からのずれを算出する方法について説明する。 半導体レー ザ 1より出射された光信号を直接に検出している光強度モニタ信号 S 2およびフ アブリペロー共 ϋ器 3を透過した光信号を検出している光強度モニタ信号 S 1は、 半導体レーザ 1より出射される光信号の強度に比例して変化する。 基準波長; L 0 力 らのずれを検出するために、 信号強度比 S 1 / S 2を算出する。 光強度モニタ 信号 S 1、 S 2は、 半導体レーザ 1より出射される光強度信号の大きさに依存す るので、 これらの信号強度比 S 1 / S 2は、 フアブリペロー共振器 3の透過率の みに依存した値となる。  Next, a method of calculating a deviation from the reference wavelength; L0 will be described. The light intensity monitor signal S2 that directly detects the optical signal emitted from the semiconductor laser 1 and the light intensity monitor signal S1 that detects the optical signal transmitted through the Fabry-Perot resonator 3 are the semiconductor laser It changes in proportion to the intensity of the optical signal emitted from 1. Calculate the signal intensity ratio S 1 / S 2 to detect the deviation from the reference wavelength; L 0 force. Since the light intensity monitor signals S 1 and S 2 depend on the magnitude of the light intensity signal emitted from the semiconductor laser 1, the signal intensity ratio S 1 / S 2 is the ratio of the transmittance of the Fabry-Perot resonator 3. It depends on the value.
フアブリペロー共振器 3の透過率は基準波長え 0を含むス口ープ内においては、 波長に対して一意に定まるので、 半導体レーザ 1より出射された光信号の波長が λ 0を含むス口ープ内にあれば、 信号強度比 S 1 / S 2の値が光信号の波長を表 すことになる。 特に、 F S Rの 1 / 2が半導体レーザ 1の波長可変領域よりも十 分大きく、 波長可変領域が; L 0を含む 1つのスロープ内に含まれていれば、 ファ ブリペロー共振器 3を絶対波長モニタとして利用することができる。 基準波長え 0での信号強度比 S 1 / S 2を予め求め、 この基準波長 λ 0での信号強度比 S 1 / S 2を波長検出部 5 1に記憶しておく。 波長検出部 5 1では、 記憶している基準 波長; I 0での信号強度比 S 1 / S 2と、 第 1、 第 2のフォトダイオード 4、 5か らの光強度モニタ信号 S 1、 S 2に基づき求めた信号強度比 S 1 / S 2との差を 求めることにより、 発振波長と基準波長; L 0とのずれ （偏差） を算出する。 この 算出された偏差信号は、 レーザ制御部 5 2に入力される。 Since the transmittance of the Fabry-Perot resonator 3 is uniquely determined with respect to the wavelength in the mouth including the reference wavelength 0, the wavelength of the optical signal emitted from the semiconductor laser 1 includes the wavelength λ 0. If it is within the range, the value of the signal intensity ratio S1 / S2 indicates the wavelength of the optical signal. In particular, if the half of the FSR is sufficiently larger than the wavelength tunable region of the semiconductor laser 1 and the wavelength tunable region is included in one slope including L0, The Brillouin resonator 3 can be used as an absolute wavelength monitor. The signal intensity ratio S 1 / S 2 at the reference wavelength 0 is obtained in advance, and the signal intensity ratio S 1 / S 2 at the reference wavelength λ 0 is stored in the wavelength detector 51. In the wavelength detector 51, the stored reference wavelength; the signal intensity ratio S 1 / S 2 at I 0, and the light intensity monitor signals S 1, S S from the first and second photodiodes 4 and 5 The difference (deviation) between the oscillation wavelength and the reference wavelength; L 0 is calculated by calculating the difference between the signal intensity ratio S 1 / S 2 obtained based on Step 2. The calculated deviation signal is input to the laser control unit 52.
次にレーザ制御部 5 2の動作について説明する。 レーザ制御部 5 2では、 波長 検出部 1から入力される偏差信号を用いて、 温度もしくは注入電流等の値を変 化させる制御信号 Τ 1を半導体レーザ 1に出力することにより、 半導体レーザ 1 の波長を制御する。  Next, the operation of the laser control unit 52 will be described. The laser controller 52 uses the deviation signal input from the wavelength detector 1 to output a control signal Τ1 for changing the value of the temperature, the injection current, or the like to the semiconductor laser 1, thereby controlling the semiconductor laser 1. Control the wavelength.
半導体レーザ 1の注入電流を変化させることにより波長を制御する場合、 一般 的に注入電流を増加し半導体レーザ 1の出力を高くすると、 半導体レーザ 1の発 振波長は長くなる。 この場合、 レーザ制御部 5 2では、 波長検出部 5 1からの偏 差信号を受けたとき、 発振波長が基準波長よりも長波長側にずれていれば、 半導 体レーザ 1への注入電流を減少させ、 発振波長が基準波長よりも短波長側にずれ ていれば、 半導体レーザ 1への注入電流を増加させるような制御信号 Τ 1を半導 体レーザ 1に送る。 - 半導体レーザ 1の温度を変化させることにより波長を制御する場合、 一般的に 温度を高くすると、 半導体レーザ 1の発振波長は長くなる。 この場合、 レーザ制 御部 5 2では、 波長検出部 5 1から偏差信号を受けたとき、 発振波長が基準波長 よりも長波長側にずれていれば、 半導体レーザ 1の温度を高くし、 発振波長が基 準波長よりも短波長側にずれていれば、 半導体レーザ 1の温度を低くするような 制御信号 Τ 1を半導体レーザ 1に送る。  When the wavelength is controlled by changing the injection current of the semiconductor laser 1, generally, when the injection current is increased and the output of the semiconductor laser 1 is increased, the oscillation wavelength of the semiconductor laser 1 becomes longer. In this case, when the laser control unit 52 receives the deviation signal from the wavelength detection unit 51 and the oscillation wavelength is shifted to a longer wavelength side than the reference wavelength, the injection current into the semiconductor laser 1 is increased. If the oscillation wavelength is shifted to a shorter wavelength side than the reference wavelength, a control signal Τ 1 for increasing the injection current to the semiconductor laser 1 is sent to the semiconductor laser 1. -When controlling the wavelength by changing the temperature of the semiconductor laser 1, generally, the higher the temperature is, the longer the oscillation wavelength of the semiconductor laser 1 is. In this case, when the laser control section 52 receives the deviation signal from the wavelength detection section 51, if the oscillation wavelength is shifted to a longer wavelength side than the reference wavelength, the temperature of the semiconductor laser 1 is increased, and If the wavelength is shifted to a shorter wavelength side than the reference wavelength, a control signal # 1 for lowering the temperature of the semiconductor laser 1 is sent to the semiconductor laser 1.
なお、 上記の説明では、 レーザ光の偏光方向を ρ偏光としたが、 s偏光のレー ザ光、 つまり C軸と光軸によって作られた平面に対して垂直な方向に偏光方向を もつレーザ光を一軸性複屈折結晶に入射するようにしても、 式 （7 ) の温度補償 条件を満足させることができる。 すなわち、 上記式 （7) は常光軸および異常光 軸の両方について満足する。 このように、 常光軸にレーザ光の偏光方向を揃えた 場合、 別言すれば、 レーザ光の光軸と偏光方向とで作られる平面に対して垂直な 面内に C軸があるようにした場合は、 光軸と C軸とのなす角度 φ cは 57. 05 度となる。 なお、 常光軸を用いた場合の屈折率 nおよび dn/d tは角度 φ cに 依存せず、 常に一定値をとる。 そして、 この場合は、 式 （7) 中の線膨張率 の みが角度 Φ cによって変化する。 In the above description, the polarization direction of the laser light is ρ polarization. However, s-polarized laser light, that is, laser light having a polarization direction perpendicular to the plane formed by the C axis and the optical axis. Is applied to the uniaxial birefringent crystal, the temperature compensation of equation ( 7) The condition can be satisfied. That is, the above equation (7) is satisfied for both the ordinary optical axis and the extraordinary optical axis. In this way, when the polarization direction of the laser light is aligned with the ordinary optical axis, in other words, the C axis is set in a plane perpendicular to the plane formed by the optical axis and the polarization direction of the laser light. In this case, the angle φ c between the optical axis and the C axis is 57.05 degrees. Note that the refractive index n and dn / dt when the ordinary optical axis is used do not depend on the angle φc and always take a constant value. Then, in this case, only the coefficient of linear expansion in equation (7) changes with the angle Φ c.
以上で明らかなように、 この実施の形態 1によれば、 フアブリべ口一共振器 3 を構成 るー軸性複屈折結晶 （例えば — BBO (B a-B204) ) を、 C軸が レーザ光の光軸と偏光方向とで作られる平面内にあるいは該平面に垂直な面内に にあり、 力 この C軸が光軸に対して一定の傾きを持つように配置するように構 成したので、 このフアプリペロー共振器 3は温度補償機能 （フアプリペロー共振 器 3から出射した信号光の強度がその温度に依存しない機能） を有することがで き、 光信号の波長にのみ依存する光強度モニタ信号 S 1を検出しモニタすること ができる。 また、 検出した光強度モニタ信号 S 1に基づき半導体レーザ 1から出 射される光信号の波長を所望の基準波長 λ 0に制御することができる。 さらに、 一材料の一軸性複屈折結晶のみを用いたので、 半導体レーザ装置の構成は簡略化 でき、 ff成が簡略ィ匕されているので、 波長モニタとしての信頼 を向上させるこ とが可能となる。 As can be seen from the above description, according to the first embodiment, constitute a Fabry base mouth one resonator 3 Lou Jikusei birefringent crystal (e.g. - BBO (B aB 2 0 4 )) , and the laser beam C axis In the plane formed by the optical axis and the direction of polarization of the optical axis, and in the plane perpendicular to the plane, the force is arranged so that the C axis has a constant inclination with respect to the optical axis. However, the resonator 3 can have a temperature compensation function (a function in which the intensity of the signal light emitted from the resonator 3 does not depend on the temperature), and the light intensity monitor signal S depends only on the wavelength of the optical signal. 1 can be detected and monitored. Further, the wavelength of the optical signal emitted from the semiconductor laser 1 can be controlled to a desired reference wavelength λ 0 based on the detected light intensity monitor signal S 1. Furthermore, since only a uniaxial birefringent crystal of one material is used, the configuration of the semiconductor laser device can be simplified, and since the configuration is simplified, the reliability as a wavelength monitor can be improved. Become.
上記実施の形態 1では、 フアブリぺロ一共振器 3の材料として — B B O結晶 を用いたが、 その材料として a— BBO(B a Β204)結晶を用いた場合におい ても温度補償条件式 （7) を満たすことができる。 In the first embodiment, as the material of the Fabry Perot one resonator 3 - was used BBO crystal, a- BBO (B a Β 2 0 4) Temperature compensation condition even odor when using the crystals as the material Equation (7) can be satisfied.
すなわち、 α— BBO結晶の場合、 異常光軸にレーザ光の偏光を揃えたときに は、 φ (2 = 64. 35度となり、 常光軸にレーザ光の偏光を揃えたときには、 φ c = 76. 95度となる。  That is, in the case of α-BBO crystal, φ (2 = 64.35 degrees) when the polarization of the laser beam is aligned with the extraordinary optical axis, and φ c = 76 when the polarization of the laser beam is aligned with the ordinary optical axis. 95 degrees.
なお、 このとき、 α— BBOの物性定数は、 異常光屈折率 ne が 1. 5300 3で、 常光屈折率 noが 1. 6502で、 熱光学係数 d no/d Tがー 9. 3 X 1 0一6/ Kで、 熱光学係数 d ne/dTが 1 6. 6 X 10— 6/Kで、 線膨張係数 は 36. 0 X 10_6/Kで、 線膨張係数 は 4. 0X 10— 6/Kである。 At this time, the physical constants of α-BBO are: extraordinary refractive index ne is 1.53003, ordinary refractive index no is 1.6650, and thermo-optic coefficient d no / d T is -9.3 X 1 0 one 6 / K, a thermal optical coefficient d ne / dT is 1 6. 6 X 10- 6 / K , the linear expansion coefficient in 36. 0 X 10_ 6 / K, the linear expansion coefficient 4. 0X 10- 6 / K.
また、 第 3図におけるフアブリペロー共振器 3の材料に L i I O 3の結晶を用 レ、た場合においても温度補償条件式 （7) を満たすことができる。 第 11図は、 異常光軸にレーザ光の偏光を揃えたときの、 L i 103結晶の式 （7) を示す d n/dT+αη の角度 ψ cに対する依存性を示すグラフである。 この第 1 1図によ れば、 L i I 03結晶を用い、 異常光軸にレーザ光の偏光を揃えた場合には、 温 度補償条件 d n/dT+an=0を満たす角度 φ cを 22. 70度と決定すること ができ なお、 L i I 03結晶を用い、 常光軸にレーザ光の偏光を揃えた場合 には、 温度補償条件 dn/dT+an-Oを満たす角度 ψ cは 18. 65度である。 さらに、 一軸性複屈折結晶として、 C a C〇3結晶を用いることもできる。 C a C03結晶の場合は、 常光軸方向のみ温度補償条件を満足し、'そのときの dn /dT+an=0を満たす角度 φ cは 67. 5度となる。 In addition, the temperature compensation conditional expression (7) can be satisfied even when a crystal of Li IO 3 is used as the material of the Fabry-Perot resonator 3 in FIG. FIG. 11 is abnormal to the optical axis of the laser light when aligned in polarization is a graph showing the dependence on the angle [psi c of dn / dT + αη showing the expression (7) of the L i 10 3 crystals. The first 1 by the FIG lever, L i I 0 3 with crystal, when aligned polarization of the laser beam on the extraordinary optical axis, the angle that satisfies the temperature compensation condition dn / dT + a n = 0 φ c Can be determined to be 22.70 degrees. In the case where the L i I 0 3 crystal is used and the polarization of the laser beam is aligned with the ordinary optical axis, the angle satisfying the temperature compensation condition dn / dT + an-O ψ c is 18.65 degrees. Furthermore, a C a C 3 crystal can be used as the uniaxial birefringent crystal. For C a C0 3 crystal satisfies the ordinary axial only temperature compensation condition, 'the angle phi c satisfying dn / dT + an = 0 at this time becomes 67.5 degrees.
この他にも、 フアブリペロー共振器の温度補償条件式 （7) を満たす材料であ れば、 他の任意の一軸性複屈折結晶を用いても良い。 また、 第 3図に示された波 長モニタ装置と第 12図に示された波長制御装置を組み合わせることにより、 波 長安定化光源を構成することが可能である。  In addition, any other uniaxial birefringent crystal may be used as long as the material satisfies the temperature compensation conditional expression (7) for the Fabry-Perot resonator. Further, by combining the wavelength monitoring device shown in FIG. 12 with the wavelength monitoring device shown in FIG. 3, it is possible to configure a wavelength stabilized light source.
第 13掘は、 この発明の実施の形態 1の変更態様による波長モニタ装置を示す 構成図である。 第 13図に示す波長モニタ装置においては、 フアブリペロー共振 器 3の上方に位置する第 2のフォトダイオード 5を、 レンズ 2との間隔を狭める ように第 1のフォトダイオード 4よりも前方に配置する。 すなわち、 この場合は、 ベースキャリア 6の第 2のフォトダイオード 5を設置する箇所を、 半導体レーザ 1のほうにせり出すように構成しており、 ベースキャリア 6の第 1のフォトダイ ォード 4を設置する箇所とベースキャリア 6の第 2のフォトダイオード 5を設置 する箇所との間には、 段差部を形成している。  The thirteenth excavation is a configuration diagram showing a wavelength monitor according to a modification of the first embodiment of the present invention. In the wavelength monitoring device shown in FIG. 13, the second photodiode 5 located above the Fabry-Perot resonator 3 is arranged ahead of the first photodiode 4 so as to reduce the distance from the lens 2. That is, in this case, the location where the second photodiode 5 of the base carrier 6 is installed is protruded toward the semiconductor laser 1, and the location where the first photodiode 4 of the base carrier 6 is installed is A step is formed between the base carrier 6 and the position where the second photodiode 5 is installed.
このようにこの第 13図の構成によれば、 第 2のフォトダイオード 5を、 第 1 のフォトダイオード 4よりも前方に配置しているので、 たとえ光信号がフアブリ ぺ口一共振器 3に入射された後、 ベースキャリア 6の底面で散乱しても、 散乱光 がフアブリペロー共振器 3を透過した後、 第 2のフォトダイオード 5で受光され ることがなくなる。 As described above, according to the configuration of FIG. 13, since the second photodiode 5 is arranged ahead of the first photodiode 4, even if the optical signal is (4) Even if the light is scattered on the bottom surface of the base carrier 6 after being incident on the single-cavity 3, the scattered light is not received by the second photodiode 5 after passing through the Fabry-Perot resonator 3.
実施の形態 2 . Embodiment 2
実施の形態 1においては、 光信号を受光するフォトダイォードが 2個設置され、 それぞれのフォトダイオードにおいて、 光信号の波長および強度のモニタをおこ なっていた。 これに対し、 実施の形態 2においては、 フォトダイオードを 3個酉己 置し、 2個のフアブリペロー共振器を上下に並列に配置することにより、 3個配 置されたニフォトダイォードのうちの 2個のフォトダイォードを用いて、 広帯域お ょぴ狭帯域における光信号の波長をモニタし、 1個のフォトダイオードを用いて 光強度信号のモニタを行うようにしている。  In the first embodiment, two photodiodes for receiving an optical signal are provided, and each photodiode monitors the wavelength and the intensity of the optical signal. On the other hand, in the second embodiment, three photodiodes are arranged independently, and two Fabry-Perot resonators are vertically arranged in parallel, so that the three photodiodes arranged in three are arranged. Two photodiodes are used to monitor the wavelength of an optical signal in a wide band or a narrow band, and one photodiode is used to monitor an optical intensity signal.
第 1 4図はこの発明の実施の形態 2による波長モ二タ装置を示す構成図である。 なお、 この実施の形態 2の構成要素のうち、 実施の形態 1の波長モニタ装置の構 成要素と共通するものについては同一符号を付し、 その部分の説明を省略する。 半導体レーザ 1は第 1 5図に示されている波長制御装置 6 0力 ら送られる制御 信号 T 1により、 温度および注入電流等が調節され、 波長が制御される。 フアブ リベロ一共振器 2 1はフアブリべ口一共振器 3と同じく、 実施の形態 1において 示された温度補償機能を持つように切り出された一軸性複屈折結晶 (例えば - B Β〇）を材料とし、 その入射面および出射面に反射膜 2 3および 2 4を有する。 この場合、 下側に配置されるフアブリペロー共振器 3の Ζ方向の厚みを、 上側 に配置されるフアブリペロー共振器 2 1の厚みよりも大きくし、 これによりファ プリペロー共振器 3を狭帯域高精度モニタ用とし、 フアブリペロー共振器 2 1を 広帯域モニタ用としている。 第 3のフォトダイオード 2 2はフアブリペロー共振 器 2 1を透過した光信号強度を検出するものであり、 第 1のフォトダイオード 4 と第 2のフォトダイォード 5の中間に配置される。 FIG. 14 is a configuration diagram showing a wavelength monitor device according to Embodiment 2 of the present invention. Note that, of the components of the second embodiment, the same components as those of the wavelength monitoring device of the first embodiment are denoted by the same reference numerals, and the description of those portions will be omitted. The temperature and injection current of the semiconductor laser 1 are controlled by the control signal T1 sent from the wavelength control device 60 shown in FIG. 15 to control the wavelength. Like the Fabry-Bay resonator 3, the Fabry-Bellow resonator 21 is made of a uniaxial birefringent crystal (eg, -B-) cut out to have the temperature compensation function shown in the first embodiment. It has reflection films 23 and 24 on its entrance surface and exit surface. In this case, the Ζ direction of thickness of Fuaburipero resonator 3 disposed on the lower side, and larger than Fuaburipero resonator 2 1 of thickness disposed above, thereby narrow band high-precision monitoring file Puripero resonator 3 and use, and the Fuaburipero resonator 2 1 and a broadband monitor. The third photodiode 22 detects the intensity of the optical signal transmitted through the Fabry-Perot resonator 21, and is arranged between the first photodiode 4 and the second photodiode 5.
次に第 1 4図の波長モニタ装置の動作の説明を行う。 半導体レーザ丄を出射し た光信号はレンズ 2で集光され平行光に変換される。 第 1のフォ.トダイォード 4 においては、 フアブリペロー共振器 （狭帯域用） 3を透過した光信号強度が検出 され、 第 3のフォトダイオード 22においてはフアブリペロー共振器 （広帯域用 ) 21を透過した光信号強度が検出される。 第 1のフォトダイオード 4で検出さ れた光強度モニタ信号を S 1とし、 第 3のフイトダイオード 22で検出された光 強度モニタ信号を S 3とし、 第 2のフォトダイオード 5で検出された光強度モニ タ信号を S 2とする。 光強度モニタ信号 S l、 S 2および S 3は、 第 15図に示 される波長制御装置 60に送られる。 波長制御装置 60は、 これらの信号 S 1、 S.2および S 3を用いて発振波長を検出し、 この検出波長に基づき半導体レーザ 1より 射される光信号の波長を制御するための制御信号 T 1を形成し、 この制 御信号 τ 1を半導体レーザ 1に出力する。 Next, the operation of the wavelength monitor shown in FIG. 14 will be described. The optical signal emitted from the semiconductor laser 集 光 is condensed by the lens 2 and converted into parallel light. First Photo Diode 4 In, the intensity of the optical signal transmitted through the Fabry-Perot resonator (for narrow band) 3 is detected, and the intensity of the optical signal transmitted through the Fabry-Perot resonator (for wide band) 21 is detected in the third photodiode 22. The light intensity monitor signal detected by the first photodiode 4 is S1, the light intensity monitor signal detected by the third photodiode 22 is S3, and the light intensity monitor signal is detected by the second photodiode 5. The light intensity monitor signal is S2. The light intensity monitor signals S1, S2 and S3 are sent to the wavelength control device 60 shown in FIG. The wavelength control device 60 detects the oscillation wavelength using these signals S1, S.2, and S3, and controls the control signal for controlling the wavelength of the optical signal emitted from the semiconductor laser 1 based on the detected wavelength. T 1 is formed, and this control signal τ 1 is output to the semiconductor laser 1.
第 16図は、 狭帯域用のフアブリぺロ一共振器 3およぴ広帯域用のフアブリぺ ロー共振器 21のそれぞれの波長透過特性を示すものである。  FIG. 16 shows the wavelength transmission characteristics of the narrow-band Fabry-roll resonator 3 and the wide-band Fabry-low resonator 21.
第 16図に示すように、 狭帯域用のフアブリペロー共振器 3の FSRは、 広帯 域用のフアブリぺロ一共振器 21の F S Rに比べて非常に小さくなるように、 そ れらの共振器長を設定する。 また、 広帯域用のフアブリペロー共振器 21の FS Rの半分すなわち波長弁別領域は、 半導体レーザ 1の波長可変範囲よりも大きく、 半導体レーザ 1の波長可変範囲がフアブリペロー共振器 21の FSR内の 1つの スローブ内に収まっているとする。 例えば、 狭帯域用のフアブリペロー共振器 3 の FSRが 20THz、 反射膜の強度反射率は 30。/。であり、 広帯域用のフアブ リペロー共振器 21の FSRが 100GHz、 反射膜の強度反射率は 30 %であ るとする。  As shown in FIG. 16, the FSR of the Fabry-Perot resonator 3 for the narrow band is very small compared to the FSR of the Fabry-Perot resonator 21 for the wide band so that Set the length. Further, half of the FSR of the Fabry-Perot resonator 21 for a wide band, that is, the wavelength discrimination region is larger than the wavelength tunable range of the semiconductor laser 1, and the wavelength tunable range of the semiconductor laser 1 is one slope in the FSR of the Fabry-Perot resonator 21. Suppose it is inside. For example, the Fabry-Perot resonator 3 for narrow band has an FSR of 20 THz, and the intensity reflectance of the reflective film is 30. /. It is assumed that the FSR of the broadband Fabry-Perot resonator 21 is 100 GHz and the intensity reflectance of the reflection film is 30%.
次に、 第 15図に示す波長制御装置 60の構成について説明する。 波長制御装 置 60は、 波長検出部 61およびレーザ制御部 52により構成される。 波長検出 部 61には、 第 1〜第 3のフォトダイオード 4， 5， 22からの光強度モニタ信 号 S 1、 S 2、 S 3と、 基準波長 λ 0が入力される。 波長検出部 61は、 光強度 モニタ信号 S l、 S 2、 S 3によって半導体レーザ 1より出射されている光信号 の発振波長を求め、 この発振波長と基準波長 λ 0との差を求める。 レーザ制御部 5 2には、 波長検出部 6 1力 ら基準波長 λ 0と半導体レーザ 1から出射された発 振波長との差が入力され、 レーザ制御部 5 2は、 その差に応じて発振波長が基準 波長; L 0に一致するように半導体レーザ 1の温度や注入電流等を制御するための 制御信号 Τ 1·を求め、 この制御信号 Τ 1を半導体レーザ 1に出力する。 Next, the configuration of the wavelength control device 60 shown in FIG. 15 will be described. The wavelength control device 60 includes a wavelength detection unit 61 and a laser control unit 52. The wavelength detector 61 receives light intensity monitor signals S 1, S 2, S 3 from the first to third photodiodes 4, 5, and 22 and a reference wavelength λ 0. The wavelength detecting unit 61 obtains the oscillation wavelength of the optical signal emitted from the semiconductor laser 1 based on the light intensity monitor signals S1, S2, and S3, and obtains the difference between this oscillation wavelength and the reference wavelength λ0. Laser controller The difference between the reference wavelength λ0 from the wavelength detector 61 and the oscillation wavelength emitted from the semiconductor laser 1 is input to 52, and the laser controller 52 sets the oscillation wavelength as a reference according to the difference. A control signal Τ 1 · for controlling the temperature, injection current, and the like of the semiconductor laser 1 is determined so as to match the wavelength; L 0, and the control signal Τ 1 is output to the semiconductor laser 1.
波長検出部 6 1の動作について詳細に説明する。 はじめに、 波長検出部 6 1は、 広帯域用のフアブリペロー共振器 2 1を透過した光強度モニタ信号 S 3を用いて 基準波長； L 0とのずれを検出する。 すなわち、 俞述したように、 波長検出部 6 1 は、 広帯域用のフアブリペロー共振器 2 1の波長透過特性を用いて予め求めてお いた基準波長； I 0での信号強度比 S 1 / S 2と、 第2および第 3のフォトダイォ ード 5、 2 2からの光強度モニタ信号 S 2、 S 3に基づき求めた信号強度比 S 3 / S 2との差を求めることにより、 発振波長と基準波長; L 0とのずれ （偏差） を 算出する。 The operation of the wavelength detector 61 will be described in detail. First, the wavelength detector 61 detects a deviation from the reference wavelength; L0 using the light intensity monitor signal S3 transmitted through the Fabry-Perot resonator 21 for a wide band. That is, as described above, the wavelength detection unit 61 is configured to calculate the signal intensity ratio S 1 / S 2 at the reference wavelength previously obtained using the wavelength transmission characteristics of the Fabry-Perot resonator 21 for a wide band. And the signal intensity ratio S 3 / S 2 obtained based on the light intensity monitor signals S 2, S 3 from the second and third photodiodes 5, 22 to obtain the oscillation wavelength and the reference Calculate the deviation (deviation) from the wavelength; L 0.
このずれ量が狭帯域用のフアブリべ口一共振器 3のスロープ幅よりも大きけれ ば、 この値がそのままレーザ制御部 5 2へ送られる。 し力 し、 光強度モニタ信号 S 3、 S 2を用いて算出した基準波長; I 0からのずれ量が、 狭帯域用のフアブリ ぺ口一共振器 3のスロープ幅よりも小さければ、 狭帯域用のフアブリぺロ一共振 器 3のスロープ特性を用いて、 基準波長; I 0からのずれ量を再度計算することに より、 よ—り高精度に発振波長を検出する。 すなわち、 狭帯域用のフアブリペロー 共振器 3の波長透過特性を用いて予め算出した基準波長; L 0での信号強度比 S 1 / S 2と、 第 1およぴ第 2のフォトダイオード 4、 5からの光強度モニタ信号 S 1、 S 2に基づき求めた信号強度比 S 3 / S 2との差を求めることにより、 発振 波長と基準波長 λ 0とのずれ （偏差） を算出する。 このようにして求められたず れ量 （偏差信号） がレーザ制御部 5 2へ送られる。  If this deviation amount is larger than the slope width of the narrow-band Fabry-Bore-One resonator 3, this value is sent to the laser control unit 52 as it is. The reference wavelength calculated using the light intensity monitor signals S3 and S2; if the deviation from I0 is smaller than the slope width of the narrow-band fiber-optic resonator 3, narrow band The oscillation wavelength is detected with higher accuracy by calculating again the amount of deviation from the reference wavelength; I0 using the slope characteristic of the fiber optic resonator 3 for use. That is, a reference wavelength calculated in advance using the wavelength transmission characteristics of the Fabry-Perot resonator 3 for the narrow band; the signal intensity ratio S 1 / S 2 at L 0, and the first and second photodiodes 4 and 5 The difference (deviation) between the oscillation wavelength and the reference wavelength λ 0 is calculated by calculating the difference between the signal intensity ratio S 3 / S 2 obtained based on the light intensity monitor signals S 1 and S 2 from. The deviation amount (deviation signal) thus obtained is sent to the laser control unit 52.
レーザ制御部 5 2は、 先の実施の形態 1と同様に動作する。 すなわち、 レーザ 制御部 5 2では、 波長検出部 6 1から入力される偏差信号を用いて、 温度もしく は注入電流等の値を変化させる制御信号 Τ 1を半導体レーザ 1に出力することに より、 半導体レーザ 1の波長を制御する。 広帯域用のフアブリペロー共振器 2 1の F S R内にある 1つのスロープは半導 ' 体レーザ 1の波長可変領域よりも大きいため、 広帯域にわたり絶対波長をモニタ することができる。 し力 し、 広帯域用のフアブリペロー共振器 2 1の波長透過特 性は、 第 1 6図にも示すように、 狭帯域用のフアブリペロー共振器 3の波長透過 特性よりも、 波長変化に対する信号強度変ィヒが小さい。 すなわち、 光強度モニタ 信号 S 3は、 光強度モニタ信号 S 1に比べ、 波長変化に対する信号強度変化が小 さレ、。 Laser control unit 52 operates in the same manner as in the first embodiment. That is, the laser control unit 52 outputs a control signal Τ1 for changing the value of the temperature or the injection current to the semiconductor laser 1 using the deviation signal input from the wavelength detection unit 61. The wavelength of the semiconductor laser 1 is controlled. Since one slope in the FSR of the Fabry-Perot resonator 21 for a wide band is larger than the wavelength tunable region of the semiconductor laser 1, the absolute wavelength can be monitored over a wide band. However, as shown in FIG. 16, the wavelength transmission characteristic of the Fabry-Perot resonator 21 for a wide band is more variable than the wavelength transmission characteristic of the Fabry-Perot resonator 3 for a narrow band. Eich is small. That is, the light intensity monitor signal S3 has a smaller signal intensity change with respect to the wavelength change than the light intensity monitor signal S1.
そのため、 S 3 / S 2の値が設定された値からずれた場合、 S 1 / S 2が同じ値 だけず;^た場合に比べて波長が大きくずれてしまうことになる。 そこで、 狭帯域 用の波長モニタであるフアブリペロー共振器 3を透過した光信号強度 S 1を用い ることにより、 半導体レーザ 1より出射された光信号の波長をより精度良く固定 することができる。  Therefore, when the value of S 3 / S 2 deviates from the set value, the wavelength is largely shifted as compared with the case where S 1 / S 2 does not have the same value; Therefore, the wavelength of the optical signal emitted from the semiconductor laser 1 can be fixed more accurately by using the optical signal intensity S1 transmitted through the Fabry-Perot resonator 3, which is a wavelength monitor for a narrow band.
なお、 下側に配置するフアプリペロー共振器 3を広帯域用の波長モニタとして 用い、 上側に配置するフアブリペロー共振器 2 1を狭帯域用の波長モニタとして 用いるように各共振器 3， 2 1の共振器長を調整するようにしてもよい。  The resonators of the resonators 3 and 21 are arranged such that the lower Fabry-Perot resonator 3 is used as a wavelength monitor for a wide band and the upper Fabry-Perot resonator 21 is used as a wavelength monitor for a narrow band. The length may be adjusted.
このようにこの実施の形態 2によれば、 半導体レーザ 1から出射される光信号 の絶対波長を広帯域にわたり高精度に制御することができる。 なお、 第 1 4図に 示された波長モニタ装置と第 1 5図に示された波長制御装置を組み合わせること により、 波長安定化光源を構成することが可能である。  As described above, according to the second embodiment, the absolute wavelength of the optical signal emitted from the semiconductor laser 1 can be controlled with high accuracy over a wide band. A wavelength stabilized light source can be configured by combining the wavelength monitor shown in FIG. 15 with the wavelength monitor shown in FIG.
第 1 7図は、 この発明の実施の形態 2の変更態様による波長モニタ装置を示す 構成図である。 第 1 7図に示す波長モニタ装置においては、 フアブリペロー共振 器 3の上方に位置する第 2およぴ第 3のフォトダイオード 5、 2 2を、 レンズ 2 との間隔を狭めるように第 1のフォトダイオード 4よりも前方に配置する。 この 場合は、 ベースキヤリア 6の第 2およぴ第 3のフォトダイオード 5、 2 2を設置 する箇所を、 半導体レーザ 1のほうにせり出すように構成しており、 ベースキヤ リア 6の第 1のフォトダイオード 4を設置する箇所とベースキャリア 6の第 2お よび第 3のフォトダイオード 5、 2 2を設置する箇所との間には、 段差部を形成 している。 FIG. 17 is a configuration diagram showing a wavelength monitor according to a modification of the second embodiment of the present invention. In the wavelength monitor device shown in FIG. 17, the second and third photodiodes 5, 22 located above the Fabry-Perot resonator 3 are connected to the first photodiode so as to reduce the distance from the lens 2. It is arranged before diode 4. In this case, the location where the second and third photodiodes 5 and 22 of the base carrier 6 are installed is configured to protrude toward the semiconductor laser 1, and the first photodiode of the base carrier 6 is formed. A step is formed between the place where the diode 4 is installed and the place where the second and third photodiodes 5 and 22 of the base carrier 6 are installed. are doing.
このようにこの第 1 7図の構成によれば、 第 2およぴ第 3のフォトダイオード 5、 2 2を、 第 1のフォトダイオード 4よりも前方に配置しているので、 光信号 がフアブリぺロ一共振器 3に入射された後、 ベースキャリア 6の底面で散乱して も、 散乱光がフアブリペロー共振器 3を透過した後、 第 2および第 3のフォトダ ィオード 5、 2 2で受光されることがなくなる。 産業上の利用可能性  As described above, according to the configuration of FIG. 17, since the second and third photodiodes 5, 22 are arranged ahead of the first photodiode 4, the optical signal is not allowed. Even if the light enters the resonator 3 and scatters on the bottom surface of the base carrier 6, the scattered light passes through the Fabry-Perot resonator 3 and is received by the second and third photodiodes 5, 22 Disappears. Industrial applicability
この 明は、 光ファイバ一を利用した波長分割多重 （WDM) 通信、 高密度波 長分割多重 (DWDM) 通信に用いられる光源としての半導体レーザの波長モニ タ装置として用いて好適である。 また、 温度変動の影響を受けることなくレーザ 光の波長を高精度にモニタすることが要求され、 また構造、 組み立ての簡単化が 要求されるシステムに適している。  This invention is suitable for use as a wavelength monitor device of a semiconductor laser as a light source used in wavelength division multiplexing (WDM) communication using an optical fiber and high-density wavelength division multiplexing (DWDM) communication. In addition, it is required to monitor the wavelength of laser light with high accuracy without being affected by temperature fluctuations, and is suitable for systems that require simplification of structure and assembly.

Claims

• 請 求 の 範 囲 • The scope of the claims
1 . . 半導体レーザから出力されるレーザ光の波長をモニタする波長モニタ装置 において、 1.. In a wavelength monitoring device that monitors the wavelength of laser light output from a semiconductor laser,
前記レーザ光の光軸に垂直な面に対して光学軸が所定角度^ Sくように切り出さ れたー材料の一軸性複屈折結晶から成り、 前記レーザ光が入射する面と出射する 面とに光を反射する光反射膜を有し、 上記レーザ光の波長に応じて異なる透過強 度を有する透過光を出力するフアブリペロー共振器と、  The optical axis is cut out so as to have a predetermined angle ^ S with respect to a plane perpendicular to the optical axis of the laser light. The material is made of a uniaxial birefringent crystal. A Fabry-Perot resonator that has a light reflecting film that reflects light, and outputs transmitted light having different transmission intensities according to the wavelength of the laser light;
前記 ァブリペロー共振器の透過光に基づきレーザ光の発振波長を測定する波 長検出手段と、  Wavelength detection means for measuring an oscillation wavelength of laser light based on light transmitted through the Fabry-Perot resonator;
を備えたことを特徴とする波長モニタ装置。  A wavelength monitor device comprising:
2 . 前記半導体レーザから出力されるレーザ光は、 一方向に偏光されたもので あり、 2. The laser light output from the semiconductor laser is polarized in one direction,
上記ファブリペロー共振器を構成する一軸性複屈折結晶は、 前記レーザ光の光 軸と偏光方向とで作られる平面に対し平行な面內に光学軸があり、 この光学軸が レーザ光の光軸に対し所定の角度傾いていることを特徴とする請求の範囲第 1項 に記載の波長モニタ装置。 - The uniaxial birefringent crystal constituting the Fabry-Perot resonator has an optical axis on a plane parallel to a plane formed by the optical axis and the polarization direction of the laser light, and this optical axis is the optical axis of the laser light. The wavelength monitor device according to claim 1, wherein the wavelength monitor device is inclined at a predetermined angle with respect to. -
3 . 前記半導体レーザから出力されるレーザ光は、 一方向に偏光されたもので あり、 3. The laser light output from the semiconductor laser is polarized in one direction,
上記ファブリペロー共振器を構成する一軸性複屈折結晶は、 前記レーザ光の光 軸と偏光方向とで作られる平面に対し垂直な面内に光学軸があり、 この光学軸が レーザ光の光軸に対し所定の角度傾いていることを特徴とする請求の範囲第 1項 に記載の波長モニタ装置。  The uniaxial birefringent crystal constituting the Fabry-Perot resonator has an optical axis in a plane perpendicular to a plane formed by the optical axis and the polarization direction of the laser light, and the optical axis is the optical axis of the laser light. The wavelength monitor device according to claim 1, wherein the wavelength monitor device is inclined at a predetermined angle with respect to.
4 . 前記フアブリペロー共振器を構成する一軸性複屈折結晶は、 一軸性複屈折 結晶の屈折率、 光軸方向の線膨張係数および熱光学係数に基づき、 光学軸の光軸 に対する角度が設定されていることを特徴とする請求の範囲第 1項に記載の波長 モニタ装置。 4. The uniaxial birefringent crystal constituting the Fabry-Perot resonator has a uniaxial birefringence. 2. The wavelength monitor according to claim 1, wherein the angle of the optical axis with respect to the optical axis is set based on the refractive index of the crystal, the coefficient of linear expansion in the optical axis direction, and the thermo-optic coefficient.
5. 上記ファプリペロー共振器を構成する一軸性複屈折結晶は、 一軸性複屈折 結晶の屈折率と光軸方向の線膨張係数との積と、 熱光学係数との和が零に一致す るように光学軸の光軸に対する角度が設定されていることを特徴とする請求の範 囲第 2項に記載の波長モニタ装置。 5. The uniaxial birefringent crystal constituting the above-mentioned Fabry-Perot resonator should be such that the sum of the product of the refractive index of the uniaxial birefringent crystal and the coefficient of linear expansion in the optical axis direction and the thermo-optic coefficient is zero. 3. The wavelength monitor according to claim 2, wherein an angle of the optical axis with respect to the optical axis is set.
6. 上記フアブリペロー共振器を構成する一軸性複屈折結晶は、 一軸性複屈折 結晶の屈折率と光軸方向の線膨張係数との積と、 熱光学係数との和が零に一致す るように光学軸の光軸に対する角度が設定されていることを特徴とする請求の範 囲第 3項に記載の波長モニタ装置。 '6. The uniaxial birefringent crystal constituting the Fabry-Perot resonator must be such that the sum of the product of the refractive index of the uniaxial birefringent crystal and the linear expansion coefficient in the optical axis direction and the thermo-optic coefficient are equal to zero. 4. The wavelength monitor according to claim 3, wherein an angle of the optical axis with respect to the optical axis is set. '
7. 前記フアブリペロー共振器を構成する一軸性複屈折結晶を、 α— BBO、 β - ΒΟ, L i I〇3のいずれかとし、 α— BBOの場合は、 光学軸の光軸に 対する角度を 64. 3 5度とし、 ]3— BBOの場合は、 光学軸の光軸に対する角 度を 64—. 75度とし、 L i I O 3の場合は、 光学軸の光軸に対する角度を 22. 70度とすることを特徴とする請求の範囲第 5項に記載の波長モニタ装置。 7. uniaxial birefringent crystal constituting the Fuaburipero resonator, α - BBO, β - ΒΟ , either as L i I_〇 3, in the case of alpha-BBO, an angle against the optical axis of the optical axis 64. 3 5 degrees,] 3—In the case of BBO, the angle of the optical axis to the optical axis is 64—.75 degrees, and in the case of Li IO 3 , the angle of the optical axis to the optical axis is 22.70. 6. The wavelength monitor according to claim 5, wherein the wavelength is measured in degrees.
8. 前記フアプリペロー共振器を構成する一軸性複屈折結晶を、 α—ΒΒΟ、 /3— BBO、 L i l〇3、 C a C〇3のいずれかとし、 a— B BOの場合は、 光 学軸の光軸に対する角度を 76. 9 5度とし、 — BBOの場合は、 光学軸の光 軸に対する角度を5 7. 05度とし、 L i I O 3の場合は、 光学軸の光軸に対す る角度を 1 8. 6 5度とし、 C a C03の場合は、 光学軸の光軸に対する角度を 6 7. 5度とすることを特徴とする請求の範囲第 6項に記載の波長モニタ装置。 8. uniaxial birefringent crystal constituting the Fuapuripero resonator, α -ΒΒΟ, / 3- BBO, either as L Il_〇 3, C a C_〇 3, in the case of a- B BO, light Science the angle to the optical axis of the shaft and 76.9 5 degrees, - in the case of BBO, its angle to the optical axis of the optical axis is 5 7.05 degrees, in the case of L i IO 3, against the optical axis of the optical axis that angle is 1 8.6 5 degrees, in the case of C a C0 3, wavelength monitor according to the range 6 preceding claims, characterized in that the angle 6 7.5 degrees with respect to the optical axis of the optical axis apparatus.
9 . 前記フアブリペロー共振器を構成する一軸性複屈折結晶は、 光学軸の光軸 に対する設定角度を維持しつつ、 その光軸方向の厚みを変化させることで、 温度 補償条件を満足させてかつ波長弁別領域を調節可能であることを特徴とする請求 の範囲第 1項に記載の波長モニタ装置。 9. The uniaxial birefringent crystal constituting the Fabry-Perot resonator satisfies the temperature compensation condition and the wavelength by changing the thickness in the optical axis direction while maintaining the set angle of the optical axis with respect to the optical axis. 2. The wavelength monitor according to claim 1, wherein a discrimination area is adjustable.
1 0 . 前記半導体レーザから出射されるレーザ光のビームサイズを調節し、 調 節されたレーザ光を上記ファブリペロー共振器に出力するレンズを備えることを 特徴とする請求の範囲第 1項に記載の波長モニタ装置。 10. The lens according to claim 1, further comprising a lens that adjusts a beam size of laser light emitted from the semiconductor laser and outputs the adjusted laser light to the Fabry-Perot resonator. Wavelength monitor device.
1 1 . 前記波長検出手段は、 1 1. The wavelength detecting means,
前記フアブリペロー共振器の透過光を検出する第 1の光検出器と、  A first photodetector for detecting transmitted light of the Fabry-Perot resonator,
前記半導体レーザから出力されるレーザ光を直接検出する第 2の光検出器と、 上記第 1およぴ第 2の光検出器の検出信号の比を用いて前記レーザ光の発振波 長を検出する波長検出部と、  A second photodetector for directly detecting laser light output from the semiconductor laser, and detecting an oscillation wavelength of the laser light using a ratio of detection signals of the first and second photodetectors. A wavelength detector to perform
を備えることを特徴とする請求の範囲第 1項に記載の波長モニタ装置。  2. The wavelength monitor according to claim 1, comprising:
1 2. 前記半導体レーザおょぴフアブリペロー共振器を載置するとともに、 前 記第 2の—光検出器が第 1の光検出器より上方に位置するように前記第 1および第 2の光検出器を設置するベースキヤリァを更に備え、 1 2. The semiconductor laser and the Fabry-Perot resonator are mounted, and the first and second light detectors are arranged such that the second photodetector is located above the first photodetector. Further equipped with a base carrier for installing the vessel,
前記ベースキャリア上に載置されたフアブリペロー共振器を透過したレーザ光 が前記第 2の光;！食出器で受光されないようにフアブリべ口一共振器の高さを調節 していることを特徴とする請求の範囲第 1 1項に記載の波長モニタ装置。  The laser light transmitted through the Fabry-Perot resonator mounted on the base carrier is the second light; 12. The wavelength monitor according to claim 11, wherein the height of the Fabry-Bore-One resonator is adjusted so as not to be received by the food extraction device.
1 3 . 前記半導体レーザおょぴフアブリペロー共振器を載置するとともに、 前 記第 2の光検出器が第 1の光検出器より上方に位置するように前記第 1およぴ第 2の光検出器を設置するベースキヤリァを更に備え、 13. The semiconductor laser and the Fabry-Perot cavity are mounted, and the first and second light beams are arranged such that the second photodetector is positioned above the first photodetector. It further includes a base carrier for installing the detector,
前記ベースキヤリァ上に載置されたフアブリペロー共振器を透過したレーザ光 が前記第 2の光検出器で受光されることがないように前記第 2の光検出器を第 1 の光検出器よりもフアブリペロー共振器側に接近させて配置していることを特徴 とする請求の範囲第 1 1項に記載の波長モニタ装置。 Laser light transmitted through a Fabry-Perot resonator mounted on the base carrier Is arranged closer to the Fabry-Perot resonator side than the first photodetector so that the second photodetector is not received by the second photodetector. The wavelength monitor according to claim 11.
5 1 4 . 半導体レーザから出力されるレーザ光の波長をモニタする波長モニタ装5 1 4. A wavelength monitor that monitors the wavelength of the laser light output from the semiconductor laser.
¾J - レヽ飞、 ¾J-Ray,
前記レーザ光の光軸に垂直な面に対して光学軸が所定角度傾くように切り出さ れたー材料の一軸性複屈折結晶から成り、 前記レーザ光が入射する面と出射する 面とに光ニを反射する光反射膜を有し、 上記レーザ光の波長に応じて異なる透過強 The material is cut out so that the optical axis is inclined at a predetermined angle with respect to the plane perpendicular to the optical axis of the laser light. The material is made of a uniaxial birefringent crystal. Having a light reflection film for reflecting light, and having different transmission intensities according to the wavelength of the laser light.
10 度を有する透過光を出力する狭帯域用の第 1のフアブリべ口一共振器と、 A first Fabry-Cavity resonator for a narrow band that outputs transmitted light having 10 degrees,
前記第 1のフアプリペロー共振器に並設され、 前記レーザ光の光軸に垂直な面 に対して光学軸が所定角度傾くように切り出された一材料の一軸性複屈折結晶か ら成り、 前記レーザ光が入射する面と出射する面とに光を反射する光反射膜を有 • し、 上記レーザ光の波長に応じて異なる透過強度を有する透過光を出力する広帯 The laser comprises a uniaxial birefringent crystal of one material cut in such a manner that the optical axis is inclined at a predetermined angle with respect to a plane perpendicular to the optical axis of the laser light, the laser being arranged side by side with the first flywheel resonator. A light-reflecting film that reflects light on the surface where light is incident and on the surface from which light is emitted, and a wide band that outputs transmitted light having different transmission intensity according to the wavelength of the laser light.
15 域用の第 2のフアブリペロー共振器と、 A second Fabry-Perot resonator for region 15;
前記第 1および第 2のフアブリべ口一共振器の透過光に基づきレーザ光の発振 波長を測定する波長検出手段と、  Wavelength detection means for measuring the oscillation wavelength of the laser light based on the transmitted light of the first and second Fabry-Cavity resonators,
を備え-たことを特徴とする波長モニタ装置。 -  A wavelength monitor device comprising: -
20 1 5 . 前記半導体レーザから出力されるレーザ光は、 一方向に偏光されたもの であり、 20 15. The laser beam output from the semiconductor laser is polarized in one direction,
上記第 1および第 2のフアプリぺロ一共振器を構成する一軸性複屈折結晶は、 前記レーザ光の光軸と偏光方向とで作られる平面に対し平行な面内に光学軸があ り、 この光学軸がレーザ光の光軸に対し所定の角度傾いていることを特徴とする 25 .請求の範囲第 1 4項に記載の波長モニタ装置。  The uniaxial birefringent crystal constituting the first and second ferromagnetic resonators has an optical axis in a plane parallel to a plane formed by the optical axis and the polarization direction of the laser light, 25. The wavelength monitor according to claim 14, wherein the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser beam.
1 6 . 前記半導体レ^"ザから出力されるレーザ光は、 一方向に偏光されたもの であり、 16. The laser beam output from the semiconductor laser is polarized in one direction And
上記ファブリペロー共振器を構成する一軸性複屈折結晶は、 前記レーザ光の光 軸と偏光方向とで作られる平面に対し垂直な面内に光学軸があり、 この光学軸が レーザ光の光軸に対し所定の角度傾いていることを特徴とする請求の範囲第 1 4 項に記載の波長モ二タ装置。  The uniaxial birefringent crystal constituting the Fabry-Perot resonator has an optical axis in a plane perpendicular to a plane formed by the optical axis and the polarization direction of the laser light, and the optical axis is the optical axis of the laser light. 15. The wavelength monitor device according to claim 14, wherein the wavelength monitor device is inclined at a predetermined angle with respect to the wavelength monitor.
1 7. 広帯域用の第 2のフアブリペロー共振器の波長弁別領域が半導体レーザ の波長可変領域より大きく、 狭帯域用の第 1のフアブリペロー共振器の波長弁別 領域が繁 1のフアプリべ口一共振器の波長可変領域に比べて十分小さくなるよう に、 第 1および第 2のフアブリべ口一共振器を構成する一軸性複屈折結晶の光軸 方向の厚みを設定することを特徴とする請求の範囲第 1 4項に記載の波長モニタ 1 7. The wavelength discrimination region of the second Fabry-Perot cavity for the broadband is larger than the wavelength variable region of the semiconductor laser, and the wavelength discrimination region of the first Fabry-Perot resonator for the narrow band is more than one. The thickness of the uniaxial birefringent crystal constituting the first and second Fabry-Bay single resonators in the optical axis direction is set so as to be sufficiently smaller than the wavelength tunable region. Wavelength monitor as described in Section 14
1 8 . 前記波長検出手段は、 前記第 1のフアブリペロー共振器の透過光を検出 する第 1の光;!食出器と、 18. The wavelength detecting means includes: a first light for detecting light transmitted through the first Fabry-Perot resonator;
前記半導体レーザから出力されるレーザ光を直接検出する第 2の光検出器と、 前記第 2のフアブリペロー共振器の透過光を検出する第 3の光検出器と、 上記第- 1および第 2の光検出器の検出信号の比および前記第 3および第 2の光 検出器の検出信号の比を用いて前記レーザ光の発振波長を検出する波長検出部と、 を備えることを特徴とする請求の範囲第 1 4項に記載の波長モニタ装置。  A second photodetector that directly detects laser light output from the semiconductor laser, a third photodetector that detects light transmitted through the second Fabry-Perot resonator, and the first and second optical detectors. A wavelength detector that detects an oscillation wavelength of the laser light using a ratio of a detection signal of a photodetector and a ratio of the detection signals of the third and second photodetectors. A wavelength monitor according to item 14 above.
1 9. 前記半導体レーザおょぴフアブリペロー共振器を載置するとともに、 前 記第 2および第 3の光検出器が第 1の光検出器より上方に位置するように前記第 1〜第 3の光検出器を設置するベースキヤリァを更に備え、 1 9. The semiconductor laser and the Fabry-Perot cavity are mounted, and the first and third optical detectors are arranged such that the second and third photodetectors are located above the first photodetector. It further includes a base carrier for installing a photodetector,
前記ベースキヤリァ上に載置されたフアブリペロー共振器を透過したレーザ光 が前記第 2および第 3の光検出器で受光されないように前記第 2および第 3の光 検出器を第 1の光検出器よりもフアブリペロー共振器側に接近させて配置してい ることを特徴とする請求の範囲第 1 4項に記載の波長モニタ装置。 The second and third photodetectors are moved from the first photodetector so that the laser light transmitted through the Fabry-Perot resonator mounted on the base carrier is not received by the second and third photodetectors. Are also located close to the Fabry-Perot resonator side. 15. The wavelength monitor according to claim 14, wherein:
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