WO2005081050A1 - 変調器集積化光源およびその製造方法 - Google Patents
変調器集積化光源およびその製造方法 Download PDFInfo
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- WO2005081050A1 WO2005081050A1 PCT/JP2005/002318 JP2005002318W WO2005081050A1 WO 2005081050 A1 WO2005081050 A1 WO 2005081050A1 JP 2005002318 W JP2005002318 W JP 2005002318W WO 2005081050 A1 WO2005081050 A1 WO 2005081050A1
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction
- G02F1/017—Structures with periodic or quasi periodic potential variation, e.g. superlattices, quantum wells
- G02F1/01708—Structures with periodic or quasi periodic potential variation, e.g. superlattices, quantum wells in an optical wavequide structure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction
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- 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
- H01S5/02—Structural details or components not essential to laser action
- H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
- H01S5/0265—Intensity modulators
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- 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
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction
- G02F1/0155—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction modulating the optical absorption
-
- 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
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/1003—Waveguide having a modified shape along the axis, e.g. branched, curved, tapered, voids
- H01S5/1014—Tapered waveguide, e.g. spotsize converter
-
- 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
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/1003—Waveguide having a modified shape along the axis, e.g. branched, curved, tapered, voids
- H01S5/1017—Waveguide having a void for insertion of materials to change optical properties
-
- 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
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/2205—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers
-
- 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
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/227—Buried mesa structure ; Striped active layer
Definitions
- the present invention relates to a modulator integrated light source in which a semiconductor laser and an electroabsorption modulator are integrated on the same substrate, and in particular, a 1.3 m band or 1.55 m used in optical fiber communication. Modulator integrated light source operating in low voltage and wide temperature range in the band. Background art
- DFB-LDs and Electro-absorption Modulators are integrated on the same semiconductor substrate, and practical use of a modulator integrated light source is progressing.
- This modulator integrated light source is mainly used as a communication light source for medium to long distance large capacity optical fibers because the wavelength fluctuation at the time of modulation is small.
- Modulator-integrated light source usually uses an EA modulator with a multi quantum well (MQW) structure.
- MQW EA modulator when a reverse bias voltage is applied, the absorption edge of the exciton (exciton) shifts to the long wavelength side (low energy side) due to the Quantum Confined Stark Effect.
- CW Continuous Wave
- CW Continuous Wave
- FIG. 1 schematically shows a standard structural example of a conventional modulator integrated light source.
- the modulator integrated light source is formed by forming the laser part and the modulator part on the same n-InP substrate 31.
- a waveguide layer 5 and an n-InP cladding layer 7 are formed on an n-InP substrate 31 along the waveguide direction, a high reflection coating 16 on one end face and a low reflection coating on the other end face 17. Each is formed.
- the diffraction grating 3 having the ⁇ Z4 phase shift structure 4 is provided.
- the active layer (quantum well) 6 of the laser section formed adjacent to the waveguide direction and the active layer (quantum well) 11 of the modulator section 11 Have.
- a P electrode 9 is formed via a cap layer 8 and a P electrode 14 is formed via a cap layer 13.
- the Yap layer 8 and the P electrode 9 constitute a laser part, and the cap layer 13 and the P electrode 14 constitute a modulation part, which are separated by an electrode separation part 15.
- An n electrode 32 facing the p electrodes 9 and 14 is formed on the back surface of the n InP substrate 31.
- the modulator section is an EA modulator applying an electroabsorption effect generated by a change in absorption coefficient due to an electric field
- a laser section is a distributed feedback semiconductor laser. It is.
- the modulator section when a reverse bias voltage is applied between the P electrode 14 and the N electrode 32, the CW light from the distributed feedback semiconductor laser is absorbed (quenched) by the above-described quantum confined Stark effect. Light modulation is performed using this absorption operation.
- the main factor limiting the modulation rate is the capacitance of the active layer and electrode pad in the modulator section. Therefore, for example, when realizing a modulation speed of lOGbZs (gigabit Z seconds) or 40 GbZs, in order to reduce the capacitance of the active layer as much as possible, usually, the modulator length L is shortened to reduce the area of the modulator. To be done. Specifically, for 10 GbZs, the modulator length L is 160 m, and for 40 Gb Zs, the modulator length L is 40 / z m, which is its 1Z4. When the modulator length is shortened, it is necessary to apply a large voltage to the modulator in order to obtain a sufficient extinction ratio (O NZOFF ratio), and a driver circuit is essential as a configuration therefor.
- O NZOFF ratio a driver circuit is essential as a configuration therefor.
- a second document (Japanese Patent No. 2540964, page 5 and FIG. 2) describes an integrated light modulator whose capacitance is further reduced.
- a high resistance substrate is used instead of the usual N or P type conductive substrate, and the structure is such that the pads of the P electrode and the N electrode do not face each other.
- the capacitance of the electrode pad portion can be reduced, the residual capacitance is only the active layer portion. Therefore, the capacitance is greatly reduced, and the modulation bandwidth determined by the CR time constant is dramatically improved.
- an extinction ratio is important as well as the modulation speed.
- the modulator is configured to absorb at a certain electric field where no absorption occurs when the applied voltage is OV, and in order to obtain good absorption, the modulator of the absorption layer (M QW) is used.
- the first document 1 discloses the relationship between the detuning amount ⁇ and the light absorption spectrum.
- the detuning amount is set to 50 to 70 nm, and it is known that the extinction ratio is the highest at this setting. The higher the extinction ratio, the higher the degree of modulation of the light to the modulation voltage. This means that it is suitable for low voltage drive.
- the drive voltage amplitude of the modulator it is necessary to set the drive voltage amplitude of the modulator to 2V-3V. Therefore, the voltage amplitude of the peripheral logic circuit (IV You need a driver to amplify
- the assumed operating temperature of the modulator integrated light source is also important.
- the absorption peak wavelength of the modulator approaches the oscillation wavelength of the distributed feedback semiconductor laser. Since the amount of detuning decreases as the operating temperature rises in this way, usually, a constant amount of detuning is maintained by maintaining the temperature constant using a Peltier device or the like so that the extinction ratio always becomes maximum. It is.
- the detuning amount may be described by the difference between the wavelength difference (nm) and the energy conversion value (meV).
- the wavelength difference force also converts the energy difference into
- the energy conversion value is 27 to 38 meV as a detuning amount at which the extinction ratio is maximized.
- the energy conversion value ( me V) When described in terms of energy conversion value ( me V), it can be expressed as a universal value depending on the wavelength band. However, in different wavelength bands, the energy conversion values are different even if the detuning amount (nm) of the same wavelength difference is obtained. For example, in the 1.55 / zm band, the detuning amount of 50 nm is 27 meV in energy difference, and the detuning amount of 50 nm in wavelength difference is 38 me in energy difference. It becomes V. Physically, if the detuning amount is equal in energy conversion value, the wavelength The characteristics are equal regardless of the band. In the following description, for convenience, all detuning amounts are described as energy conversion values.
- the third document (Milind R. Gokhale “Uncooled, lOGbZ s 1310 nm Electroabsorption Modulated Laser” (Optical Fiber Communication 2003), March 2003, Post Deadline Paper, PD — 42 (page 1, FIG. 3)) describes a modulator integrated light source that achieves non-thermal operation.
- This modulator integrated light source maintains the extinction characteristic by changing the offset voltage of the optical modulator accordingly even if the detuning amount changes with temperature.
- the Offset voltage is a central voltage of the modulation voltage signal applied to the modulator, and in general, is often defined by an applied voltage when light of 3 dB is absorbed by the modulator. According to the structure described in the third document, the amount of detuning becomes large particularly on the low temperature side, and the offset voltage of the modulator necessary for the extinction becomes as high as 4 V or more. Disclosure of the invention
- the operating voltage of the modulator is high, an amplifier (dry circuit) for obtaining the operating voltage is required.
- the voltage applied to the modulator is 2 V or more, and the peak value is 2 V or more
- the operating voltage can be reduced by increasing the modulator length, in this case, since the capacitance C of the active layer portion of the modulator becomes large, high speed operation can not be performed.
- the modulator integrated light source disclosed in the third document since the operating voltage of the modulator is high, it is disadvantageous in terms of cost and miniaturization as described above.
- the semiconductor embedded structure is a ridge structure which can not sufficiently confine light in the modulator absorption layer, the light-emitting device also has poor extinction characteristics with low absorption efficiency.
- an extinction ratio of 10 dB or more is required for the modulator integrated light source
- the extinction ratio of the modulator is as low as 6 dB and the extinction ratio of 10 dB or more. It is difficult to realize.
- An object of the present invention is to solve the above problems, eliminate the need for an amplifier (driver) and a temperature control mechanism, and obtain a sufficient extinction ratio of 10 dB or more for optical communication applications.
- a modulator integrated light source of the present invention is a modulator integrated light source in which a semiconductor laser and an electroabsorption modulator are integrated on a high resistance semiconductor substrate,
- the electroabsorption modulator includes a pair of electrodes disposed on one side of the high resistance semiconductor substrate and to which a predetermined bias voltage is applied, and the electroabsorption modulator.
- the electroabsorption modulator when the electroabsorption modulator is integrated on the high resistance semiconductor substrate, and the pair of electrodes (P electrode and N electrode) are both positioned on the same substrate surface side. Since the capacitance of the electro-absorption modulator can be regarded as the capacitance of its active layer only, the modulation speed B (Gb / s) and the modulator length L ( ⁇ m) are in inverse proportion to each other. become. In such a structure, in order to increase the modulation rate, the modulator length L is usually shortened, but in the present invention, the modulator length L is increased, and so on. .
- the modulator length L is conventionally set to less than 200 m, but in the present invention, the modulator length L is set to 200 / z m or more. In this manner, by increasing the modulator length L, more light passing through the modulator can be absorbed, so that an extinction ratio of 10 dB or more can be obtained, and an amplifier (a circuit that does not require a drain) can be obtained. That is, low voltage operation with an operating voltage of IV or less is possible.
- the above-described structure of the present invention is generally used. It is an unthinkable structure. For example, in the structures of the first and second documents, it is not suggested to increase the modulator length since the improvement of the modulation band is a problem. Thus, the present invention is a structure that can not be easily conceived conventionally.
- the oscillation wavelength and the absorption peak are at room temperature where the absorption peak wavelength of the electroabsorption modulator is shorter than the oscillation wavelength of the semiconductor laser.
- a method of manufacturing a modulator integrated light source according to the present invention is a method of manufacturing a modulator integrated light source in which a semiconductor laser and an electro-absorption type optical modulator are integrated on a high resistance semiconductor substrate.
- the active layers of the semiconductor laser and the electroabsorption modulator can be formed in separate steps, the composition, the number of quantum wells, and the band gap of each active layer can be determined. The optimization can be made and the above-mentioned modulator integrated light source of the present invention can be easily formed.
- a configuration can be realized that has an extinction ratio of 10 dB or more and does not require an amplifier (driver). Low cost can be achieved.
- the temperature control control mechanism is not required to expand the operating temperature range (for example, 0 ° C. to 85 ° C.) compared to the conventional one, power consumption is reduced accordingly. It is possible to reduce the size and cost as well as to
- FIG. 1 is a diagram showing a standard structural example of a conventional modulator integrated light source.
- FIG. 2C is a cross-sectional view taken along line BB in FIG. 2A.
- FIG. 3 is a diagram showing the relationship between the modulator length and the offset bias voltage when the modulation speed is lOGbZs.
- FIG. 5B is a cross-sectional view taken along the line AA of FIG. 5A.
- FIG. 6 is a cross-sectional view of a modulator integrated light source according to another embodiment of the present invention.
- FIG. 2A is a top view of a modulator integrated light source according to a first embodiment of the present invention
- FIG. 2B is a cross-sectional view taken along line AA of FIG. 2A
- FIG. 2C is line BB of FIG. FIG.
- the diffraction grating 3 having the ⁇ Z4 phase shift structure 4 is provided.
- the ⁇ 4 phase shift structure 4 may be symmetrical or asymmetric in phase shift position. In addition, such a ⁇ 4 phase shift structure 4 may not be provided.
- a cap layer 8 is formed in the region of the distributed feedback laser portion la on the n-InP cladding layer 7, and a cap layer 13 is formed in the region of the optical modulator portion 1b.
- the cap layers 8 and 13 are covered with a SiO 2 film 24.
- a contact is formed in the center of the region of the SiO film 24 on the cap layer 8
- a window 26 is formed, and a P electrode 9 is formed to cover the contact window 26. Similarly, a contact window 27 is formed near the center of the region of the SiO film 24 on the cap layer 13.
- the P electrode 14 is formed to cover the contact window 27.
- the P electrode 9 and the P electrode 14 are separated by an electrode separation unit 15.
- a pad 25 for the light modulator electrode wire is formed on a part of the P electrode 14.
- the portions of the active layers 6 and 11, the n-InP cladding layer 7 and the cap layers 8 and 13 formed on the n + -InP buffer layer 18 have a mesa shape.
- current blocking structures 20 and 21 are provided.
- the end of the mesa is SiO film 24
- a window 28 is formed, and an N electrode 32 is formed to cover the contact window 28.
- N The pole 32 and the P electrode 9 and the P electrode 14 are both formed on the same element surface, and are arranged not to face each other.
- a metallized layer 2 facing the P electrodes 9 and 14 and the N electrode 32 is formed on the back surface of the n-InP substrate 31.
- the P electrode 14 and the N electrode 32 are located on the same element surface side, and the high resistance semiconductor substrate 1 is used as a substrate.
- the capacitance of the modulator can be regarded as only the capacitance of the active layer 11, the modulation speed 8 (01) 73) and the modulator length 111 are in inverse proportion to each other. Become.
- the modulator length is shortened, but in the present embodiment, more light passing through the modulator can be absorbed.
- the offset voltage never falls below IV.
- the offset voltage is IV or less. That is, if the modulator length is 200 m or more, low voltage operation below IV can be achieved, and an amplifier (a configuration that does not require a drain can be realized.
- Low voltage operation is realized by setting the modulator length to 200 m or more Specifically, considering that the relationship between the modulator length L and the modulation frequency B is in inverse proportion,
- the offset voltage is always less than IV, so no amplifier is required.
- the CR limit is 25 picoseconds, that is, 40 Gb Zs. It can be seen that the upper limit of “2000 111 4001) 73” exists as the upper limit of “Shi: 6”. Therefore, considering this upper limit,
- the electrostatic capacity increases due to the lengthening of the modulator, that is, band deterioration occurs.
- a high resistance semiconductor substrate is used. In this way, it is a structure that suppresses such band degradation.
- the voltage amplitude for the modulation operation is defined, for example, by the voltage required to extinguish (off) to the intensity of 1Z10 or 1Z20 to turn off the light.
- the modulator length is increased to reduce the offset voltage, the voltage for turning off the light will also be reduced. Therefore, the decreasing tendency tends to decrease with respect to the modulator length, similarly to the offset voltage in FIG.
- the absorption peak wavelength of the modulator is emitted by the distributed feedback semiconductor laser.
- the extinction ratio is degraded due to a large shift to the shorter wavelength side than the oscillation wavelength. In this case, it is necessary to apply a large bias voltage in order to obtain good quenching.
- the absorption peak wavelength of the modulator approaches the oscillation wavelength of the distributed feedback semiconductor laser, and the absorption of the modulator portion in the absence of an electric field increases to degrade the extinction ratio.
- the modulator length is set in advance according to the above equation 1 so that a large noise voltage is not required at low temperatures.
- the detuning amount (energy conversion value) at room temperature is set in advance so that the absorption of the modulator does not increase at high temperatures.
- the modulator can operate only at around room temperature.
- the detuning amount (me V) at room temperature is set to 40 meV or more.
- the detuning amount at room temperature 20 ° C. is set to 43 meV, which is larger than the conventional 30 meV.
- the amount of detuning is about 30 meV. This detuning of about 30 meV is optimal for the operation of the modulator.
- the detuning amount is 50 meV. In this case, good extinction can be obtained by increasing the offset voltage. If the modulator length is set so that the value of the increased noise voltage at this low temperature becomes IV or less, the above-mentioned low voltage operation is not impaired.
- the diffraction grating 3 including the ⁇ / 4 phase shift structure 4 is formed on the high resistance semiconductor substrate 1 by a known photolithography method using an interference exposure method, an electron beam exposure method or the like.
- the region for forming the diffraction grating 3 is only the region operating as a distributed feedback laser.
- the waveguide layer 5 made of InGaAsP and the 18 + ⁇ ⁇ + buffer layer 18 are sequentially formed on the entire surface, and then the active layer 6 made of InGaAsPZlnGaAsP quantum well and the activity made of InGa AsPZlnGaAsP quantum well are formed thereon.
- Form layer 11 Here, InGaAlAs can be used instead of InGaAsP.
- the active layers 6 and 11 are simultaneously formed to have mutually different band gap sizes by a known selective growth method. According to the selective growth method, it is different in the substrate plane by adjusting the amount of growth loss achieved using the SiO mask.
- the active layer can be formed to have different band gap wavelengths in the distributed feedback laser portion la and the modulator portion 1b.
- the active layers 6 and 11 are formed such that their electrical conductivity is undoped (high resistance).
- the P—InP cladding layer 7 and the cap layers 8 and 13 made of P InGaAs are sequentially grown on the entire surface. Thereafter, the vicinity of the active layers 6 and 11 is etched by a known wet etching method or dry etching method to expose a part of the n + -InP buffer layer 18.
- a SiO film 24 is deposited on the entire surface, and contact windows 26-28 are formed by etching.
- the back surface of the high-resistance semiconductor substrate 1 is polished to make the thickness of the element about 100 m, and metal is deposited on the polished surface to form the metallized layer 2.
- the active layers 6 and 11 are formed by the selective growth method in the above manufacturing process, the present invention is not limited to this.
- the active layers 6 and 11 can also be formed by the butt joint method.
- the knot joint method first, an active layer having a first band gap is grown on the entire surface (including the regions of the active layers 6 and 11). Thereafter, the active layer 6 is obtained by removing a portion of the region of the active layer 11 by a known wet etching method or dry etching method. Next, an active layer having a second band gap different from the first band gap is grown only on the removed portion to obtain an active layer 11.
- the composition, the number of quantum wells, and the band gap of each of the active layers 6 and 11 can be set independently. It can be easily optimized.
- the active layer structure of the distributed feedback laser unit la and the modulator unit lb can be controlled independently, so the type ⁇ structure is applied to the quantum well of the modulator. be able to.
- a brief description of the Type II structure follows.
- the type I quantum well has a structure higher than the energy level of the conduction band of the well and the energy level of the conduction band of the barrier and lower than the energy level of the power of the valence band of the well and lower than the energy of the valence band of the barrier. Usually, both electrons and holes are confined in the well.
- the type II quantum well has the same energy level relationship of the conduction band as the structure of type I. The energy level of the valence band of the power well. Higher than the energy level of the zonules.
- the type II quantum well can be easily formed by using a composition in which the energy level of the valence band is high.
- a type II quantum well including an InP barrier in a well made of InAlAs as described in Patent 3001365 can be used.
- the electrode of the light modulator may be a traveling wave electrode structure.
- a modulator integrated light source having such a traveling wave electrode structure will be described.
- FIG. 5A is a top view of a modulator integrated light source according to a second embodiment of the present invention
- FIG. 5B is a cross-sectional view taken along line AA of FIG. 5A.
- the same components as those shown in FIGS. 2A to 2C are denoted by the same reference numerals.
- only the features will be described in order to avoid duplication of explanation.
- the modulator integrated light source of the present embodiment replaces the P electrode 14 of the modulator section lb with the traveling wave electrode 22 and An undoped InP layer 23 is provided on the active layers 6 and 11. Also in the present embodiment, by satisfying the conditions of the above-described Equation 1 (or Equation 2) and Equation 3 respectively, the amplifier and the temperature control mechanism are not required.
- the traveling wave electrode 22 is configured such that the supplied modulated electrical signal travels from the first end on the electrode separation unit 15 side to the second end located on the opposite side. Electrode structure There is. A pad 29 for the traveling wave electrode wire is formed on the first end side of the traveling wave electrode 22, and a pad 30 for the traveling wave electrode wire is formed on the second end side. According to this electrode structure, since the modulated electrical signal travels in the same direction as the light traveling direction, the modulator signal acts more effectively on the light without depending on the capacity of the active layer 11. It is possible to improve the modulation efficiency.
- the modulator is extinguished by applying a reverse bias voltage to the pn diode.
- the reverse bias voltage causes an electric field to be applied to the active layer of the modulator section which is an AND-type (high resistance), but the larger the electric field, the more the light can be quenched.
- the traveling wave electrode 22 is ideally considered to advance without changing the electric field strength as the electromagnetic wave for modulation travels through the electrode, but in reality, the traveling wave electrode 22 and the transmission line up to that point Because of the impedance mismatch between them, as the modulated electromagnetic wave travels the traveling electrode, the electric field strength of the modulated electromagnetic wave is attenuated. For this reason, the deterioration of the extinction characteristic is larger in the second half than in the first half of the modulator. In order to reduce the deterioration of the extinction characteristics in the latter half, it is necessary to make sure that the electric field strength applied to the active layer of the modulator does not attenuate even if the voltage of the electromagnetic wave decreases.
- E is an electric field applied to the undoped InP layer 23
- V is a voltage of an electromagnetic wave
- d is a thickness of the undoped InP layer 23.
- the thickness of the undoped InP layer 23 in the modulator section is gradually reduced in the traveling direction of the oscillation light. .
- the structure in which the thickness of the undoped InP layer 23 in the modulator section is changed can be realized by adjusting the diffusion amount of zinc as a p-type dopant in the waveguide direction.
- a semiconductor or dielectric which is different from the ridge waveguide structure as described in the above third document is used.
- the active layer may be formed in a buried structure.
- the embedded structure may be an undoped layer (high resistance layer). Such an embedded structure can be realized by selective growth.
- Al has a synergistic effect of improving the temperature characteristics of the distributed Bragg reflector semiconductor laser, and the operating temperature can be raised to a higher temperature.
- a window structure 33 may be provided between the active layer 11 of the light modulator section lb and the low reflection coating 17 so that they do not contact with each other. According to this structure, since the light emitted from the end of the active layer 11 is diffused in the window structure 33, the amount of light reflected by the low reflection coating 17 and returned back into the active layer 11 is significantly increased. It can be reduced.
- the window structure shown in FIG. 6 is an example applied to the structure of the first embodiment, but can be applied to the structure of the second embodiment.
- the present invention can be applied to medium-long distance light sources used for trunk systems, access systems, etc., as well as modulator integrated light sources used for data comb systems and end user terminals.
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- General Physics & Mathematics (AREA)
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- Engineering & Computer Science (AREA)
- Nanotechnology (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Electromagnetism (AREA)
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- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
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Abstract
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JP2006510204A JPWO2005081050A1 (ja) | 2004-02-20 | 2005-02-16 | 変調器集積化光源およびその製造方法 |
US10/590,029 US20070189344A1 (en) | 2004-02-20 | 2005-02-16 | Modulator-integrated light source and its manufacturing method |
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JP2007279406A (ja) * | 2006-04-07 | 2007-10-25 | Opnext Japan Inc | 半導体光変調装置 |
JP2012002929A (ja) * | 2010-06-15 | 2012-01-05 | Opnext Japan Inc | 半導体光素子の製造方法、レーザモジュール、光伝送装置 |
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CN115224584A (zh) * | 2021-04-20 | 2022-10-21 | 华为技术有限公司 | 电吸收调制激光器、光发射组件和光终端 |
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JPH07218880A (ja) * | 1994-01-31 | 1995-08-18 | Nec Corp | 光半導体素子及び光通信装置 |
JPH09133902A (ja) * | 1995-11-10 | 1997-05-20 | Nippon Telegr & Teleph Corp <Ntt> | 導波路型半導体光素子およびその製造方法 |
JP2001024289A (ja) * | 1999-07-06 | 2001-01-26 | Nippon Telegr & Teleph Corp <Ntt> | 半導体光素子 |
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US5889898A (en) * | 1997-02-10 | 1999-03-30 | Lucent Technologies Inc. | Crosstalk-reduced integrated digital optical switch |
US7075954B2 (en) * | 2001-05-29 | 2006-07-11 | Nl Nanosemiconductor Gmbh | Intelligent wavelength division multiplexing systems based on arrays of wavelength tunable lasers and wavelength tunable resonant photodetectors |
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2005
- 2005-02-16 WO PCT/JP2005/002318 patent/WO2005081050A1/ja active Application Filing
- 2005-02-16 US US10/590,029 patent/US20070189344A1/en not_active Abandoned
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JPH07218880A (ja) * | 1994-01-31 | 1995-08-18 | Nec Corp | 光半導体素子及び光通信装置 |
JPH09133902A (ja) * | 1995-11-10 | 1997-05-20 | Nippon Telegr & Teleph Corp <Ntt> | 導波路型半導体光素子およびその製造方法 |
JP2001024289A (ja) * | 1999-07-06 | 2001-01-26 | Nippon Telegr & Teleph Corp <Ntt> | 半導体光素子 |
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GOKHALE M. ET AL: "Uncooled,10Gb/s 1310 nm Electroabsorption Modulated Laser.", OFC, 2003, pages 42 - 43, XP010680622 * |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2007279406A (ja) * | 2006-04-07 | 2007-10-25 | Opnext Japan Inc | 半導体光変調装置 |
JP2012002929A (ja) * | 2010-06-15 | 2012-01-05 | Opnext Japan Inc | 半導体光素子の製造方法、レーザモジュール、光伝送装置 |
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JPWO2005081050A1 (ja) | 2008-01-10 |
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