CN108321669B - A kind of frequency multiplication light path module and the double-frequency laser system including the module - Google Patents
A kind of frequency multiplication light path module and the double-frequency laser system including the module Download PDFInfo
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- CN108321669B CN108321669B CN201810306395.6A CN201810306395A CN108321669B CN 108321669 B CN108321669 B CN 108321669B CN 201810306395 A CN201810306395 A CN 201810306395A CN 108321669 B CN108321669 B CN 108321669B
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
- H01S3/0813—Configuration of resonator
- H01S3/0816—Configuration of resonator having 4 reflectors, e.g. Z-shaped resonators
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
- H01S3/06712—Polarising fibre; Polariser
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
- H01S3/06716—Fibre compositions or doping with active elements
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06754—Fibre amplifiers
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
- H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
- H01S3/109—Frequency multiplication, e.g. harmonic generation
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- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention discloses a kind of frequency multiplication light path module and the double-frequency laser system including the module, including the second optical fiber, collimator lens FC, set the thin metal gasket of thickness, first hysteroscope CM1, second hysteroscope CM2, third hysteroscope CM3, 4th hysteroscope CM4, periodic polarized crystal under set temperature environment, the first hysteroscope CM1, second hysteroscope CM2, third hysteroscope CM3, 4th hysteroscope CM4 forms the dish-like chamber that optical path is transmitted in hysteroscope medial surface, the periodic polarized crystal is arranged in the optical path between third hysteroscope CM3 and the 4th hysteroscope CM4, on the end face for the output end that the thin metal gasket one side is attached to the second optical fiber.The advantages of invention is: the setting for setting the thin metal gasket of thickness can replace lens group and dish-like chamber progress pattern match, and the device used in this way is few, is easily integrated.
Description
Technical field
The present invention relates to laser technology, nonlinear optical physical technology field and Atomic Physics technical fields, especially a kind of
Frequency multiplication light path module and double-frequency laser system including the module.
Background technique
In double-frequency laser system, through being realized frequently with various optical path components and electronic component to frequency multiplication and optical path
Adjustment.For example, improvement product is so that product minimizes as far as possible, and often product improvement is chased after under the premise of assurance function
The target asked.
Reduce components be product miniaturization pass through frequently with technical solution because reduction components one side not only may be used
So that structure is more simple and compact, and cost can also be further reduced.Therefore, how on the basis of reducing components
Realize that preferable technical functionality becomes those skilled in the art's technical problem urgently to be resolved.
Summary of the invention
In order to overcome the above-mentioned prior art, for this purpose, the present invention provides a kind of frequency multiplication light path module and times including the module
Frequency laser system.
To achieve the above object, the invention adopts the following technical scheme:
A kind of frequency multiplication light path module, including the second optical fiber, collimator lens FC, the thin metal gasket for setting thickness, first
Periodic polarized crystal under hysteroscope CM1, the second hysteroscope CM2, third hysteroscope CM3, the 4th hysteroscope CM4, set temperature environment, institute
It states the first hysteroscope CM1, the second hysteroscope CM2, third hysteroscope CM3, the 4th hysteroscope CM4 and forms the dish that optical path is transmitted in hysteroscope medial surface
Type chamber, the periodic polarized crystal are arranged in the optical path between third hysteroscope CM3 and the 4th hysteroscope CM4；The thin metal
Gasket one side is attached on the end face of the output end of the second optical fiber, the spacing between opposite another side and collimator lens FC
For focusing distance f, the center of the first hysteroscope CM1 and the second hysteroscope CM2 line and collimator lens FC spacing are L12, described
Second optical fiber transmission optical path successively after excessively thin metal gasket and collimator lens FC from the first hysteroscope CM1 backwards to dish-like chamber
Face passes through the first hysteroscope CM1, then in turn through the second hysteroscope CM2 towards the medial surface back reflection in the middle part of dish-like chamber to third chamber
Mirror CM3 is towards the medial surface in the middle part of dish-like chamber and then is reflected into the 4th hysteroscope CM4 towards the medial surface in the middle part of dish-like chamber, frequency multiplication
Light beam passes through the 4th hysteroscope CM4 and exports from from the lateral surface in the middle part of dish-like chamber.
Optimization, in the optical path between the collimator lens FC and the first hysteroscope CM1 along the optical path direction of the launch also according to
Secondary the first reflecting mirror M1 and the second reflecting mirror M2 being provided with for adjusting optical path.
Optimization, the 4th hysteroscope CM4 is provided with dichroic mirror DM on output light path at the lateral surface in the middle part of dish-like chamber.
Optimization, second optical fiber is polarization maintaining optical fibre PMF.
Optimization, the periodic polarized crystal is PPLN.
Optimization, the periodic polarized crystal is arranged in temperature controlling stove, and the temperature range of the temperature controlling stove is 15-120
℃。
Optimization, the first hysteroscope CM1 and the second hysteroscope CM2 are average chamber, the third hysteroscope CM3 and the 4th hysteroscope
It is the flat-concave cavity of concave surface that CM4, which is towards the medial surface in the middle part of dish-like chamber,；Outside of the first hysteroscope CM1 in the middle part of dish-like chamber
Face is coated with the anti-reflection film of setting wavelength, the reflectance coating that it is T to the transmissivity of the wavelength that medial surface, which is coated with,；Second hysteroscope CM2 towards
Medial surface in the middle part of dish-like chamber is coated with the film that is all-trans of the wavelength；The third hysteroscope CM3 and the 4th concave surface hysteroscope CM4 are that setting is bent
Rate, third hysteroscope CM3 are coated with the film that is all-trans of the wavelength in curved surface towards the medial surface in the middle part of dish-like chamber, the 4th hysteroscope CM4 towards
Medial surface in the middle part of dish-like chamber is coated with the film that the wavelength is all-trans, half-wave grows tall, and the lateral surface in the middle part of dish-like chamber is coated with half
The anti-reflection film of wavelength；Periodic polarized crystal outer surface is coated with double anti-reflection films of the wavelength and half-wavelength, dish-like chamber it is best
The coefficient of coup isWherein PcIt is dish-like cavity circulation power, L is other than inputting dish-like chamber
Intracavitary linear impairments；Γ is non-linear transfer coefficient, wherein Γ=ENL+Eabs；ENLIt is the frequency multiplication in the case of once-through
Coefficient, EabsFor non-linear conversion absorption coefficient.
In various element；
The q parameter of second fiber-optic output endface is q0=iZ0=i π w02/λ；First hysteroscope CM1 and the second hysteroscope CM2
Q parameter be q1=iZ1=i π w12/λ；W0 is the core diameter of the second fiber end face, and w1 is dish-like the first intracavitary hysteroscope CM1 and the
Waist radius size between two hysteroscope CM2, i are imaginary unit, and λ is the setting wavelength of frequency multiplication, Z0And Z1For Ruili distance；
The center of first hysteroscope CM1 and the second hysteroscope CM2 line to collimator lens FC be set distance L12, L12Meet
Formula
It can be expressed as in one week total matrix of cavity circulationR is third hysteroscope CM3's and the 4th hysteroscope CM4 in formula
Radius of curvature, LcFor the length of crystal, l1For the distance of third hysteroscope CM3 and the 4th hysteroscope CM4, remaining chamber distance between mirrors is l,
Distance l is equal to one week total length of cavity circulation and subtracts the distance between third hysteroscope CM3 and the 4th hysteroscope CM4, and n is periodical pole
Change the refractive index of crystal, A2、B2、C2、D2For the various element in propogator matrix；Meeting condition | A2+D2| < 2, third hysteroscope CM3
And the 4th waist radius size between hysteroscope CM4 is
A kind of double-frequency laser system including above-mentioned frequency multiplication light path module further includes laser, the first optical fiber, optical fiber electricity
Optical modulator EOM, EDFA Erbium-Doped Fiber Amplifier EDFA, servo circuit, quick coupling PD, piezoelectric ceramics PZT, the laser pass through
First optical fiber is connect with the input terminal of fiber electro-optic modulator EOM, and the fiber electro-optic modulator EOM includes connecting with servo circuit
The first output end connect and the second output terminal being connect with EDFA Erbium-Doped Fiber Amplifier EDFA input terminal, the EDFA Erbium-Doped Fiber Amplifier
The output end of EDFA is connect with the input terminal of the second optical fiber, and lateral surface of the first hysteroscope CM1 in the middle part of dish-like chamber passes through
The connection of one input terminal of quick coupling PD and servo circuit, the output end of the servo circuit is connect with piezoelectric ceramics PZT, described
Piezoelectric ceramics is arranged on the lateral surface of the second hysteroscope CM2.
Optimization, the servo circuit includes local oscillator LO, frequency mixer M, the low-pass filter LP set gradually, ratio
Example integral-derivative controller PID, high-voltage amplifier HV, the first output end and local oscillator LO of fiber electro-optic modulator EOM
Connection, the local oscillator LO and quick coupling PD are connect with the input terminal of frequency mixer M respectively, and the low-pass filter LP is set
Set the output end in frequency mixer M.
The present invention has the advantages that
(1) in the invention, the setting for setting the thin metal gasket of thickness can replace other lens group and dish-like chamber
Pattern match is carried out, the device used in this way is few, is easily integrated.
(2) for the alignment of optical path, the directly angle of adjustment collimator lens FC when, the angle for rotating very little may be inclined
Difference is larger, and the setting of the first reflecting mirror M1 and the second reflecting mirror M2 can reduce collimator lens FC and dish-like the first intracavitary chamber
The difficulty of the optical path adjusting of mirror CM1.
(3) dichroic mirror DM is set at the lens combination light path output of dish-like chamber, so that the fundamental frequency light of double-frequency laser and leakage
Separation.
(4) powerful narrow linewidth laser is generated there are mainly two types of mode at present, and one is swashed using cavity semiconductor
Light pipe adds taper image intensifer, and this structure can produce the laser of high-power narrow line width, however semiconductor laser radiation
Facular model poor quality out, if coupling efficiency only up to reach near 60%, therefore with Single-Mode Fiber Coupling
It needs first to carry out shaping to mode in Atomic Physics experiment and nonlinear optics experiment just use.This just brings very to experiment
Big is not convenient.When using single mode optical fiber, need that four for controlling phase are added in the subsequent optical path of collimator lens FC
/ mono- wave plate QWP and half-wave plate HWP, and the present invention uses polarization maintaining optical fibre PWF, can save quarter-wave plate QWP and half
Wave plate HWP, this also reduces the numbers of components.Make the pumping laser quality of output remote by the mode that polarization maintaining optical fibre exports
Higher than the quality of the pump light exported by semiconductor TA amplifier, so that the pattern match efficiency exports laser than semiconductor TA
Pattern match efficiency it is much higher.
(5) optical axis of the periodic polarized PPLN crystal beam along crystal, the light come out without walk-off effect, frequency multiplication
Beam, mould field quality are high.The once-through frequency-doubling conversion efficiency of periodic polarized crystal is high simultaneously, reaches needed for best shg efficiency
The pump power wanted can be lower, greatly reduces the requirement to pump laser power.
(6) since the frequency-doubled wavelength of periodic polarized PPLN crystal has a certain range of tunable characteristic, work as pumping wave
It, can be under new wavelength in fact by the phase-matching temperatures that temperature controlling stove changes periodic polarized PPLN crystal when length changes
Existing optimal frequency multiplication output, the tuning range of pumping wavelength is generally in 10nm or so, when needing larger range of adjustable range,
The crystal with other polarization cycles can be replaced, chirp polarized crystal can also be used to realize that large-scale tunable wave length is special
Property.
(7) present invention by the filming parameter of each hysteroscope meets impedance matching, by adjusting between component distance or portion
Part attribute meets pattern match, to realize the Best Coupling coefficient of entire light path module, realizes stable frequency multiplication output.
(8) this system realizes the locking of dish-like chamber by PDH lock-in techniques, and this lock chamber robustness is good, dynamic range
Greatly, dish-like chamber is locked on the formant of pump light.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of double-frequency laser system in the present invention；
Fig. 2 is that the present invention utilizes thin metal gasket and the quasi- finger cooperation matched frequency multiplication light path module of implementation pattern of optical fiber
Schematic illustration；
Fig. 3 is the servo circuit schematic illustration in double-frequency laser system of the present invention；
Fig. 4 is frequency-doubling crystal temperature curve schematic diagram in the embodiment of the present invention；
Fig. 5 is the reflection schematic diagram of dish-like chamber in the embodiment of the present invention；
Fig. 6 is frequency multiplication optical power in the embodiment of the present invention with the schematic diagram of the variation of pump power.
The meaning of label symbol is as follows in figure:
The thin metal gasket 5- temperature controlling stove of 1- laser 2- the first optical fiber the second optical fiber of 3- 4-
6- periodic polarized crystal 7- servo circuit
Specific embodiment
To make the object, technical solutions and advantages of the present invention clearer, the present invention is made into one below in conjunction with attached drawing
Step ground detailed description.Obviously, described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.
This programme is by taking wavelength X is the frequency multiplication light path module of 780nm as an example.
As shown in Figs. 1-2, a kind of frequency multiplication light path module including the second optical fiber 3, collimator lens FC, sets the thin of thickness
Week under metal gasket 4, the first hysteroscope CM1, the second hysteroscope CM2, third hysteroscope CM3, the 4th hysteroscope CM4, set temperature environment
Phase property polarized crystal 6, the periodic polarized crystal 6 are arranged in temperature controlling stove 5, and the temperature range of the temperature controlling stove 5 is 15-
120 DEG C, temperature-controlled precision 2mK.Second optical fiber 3 is polarization maintaining optical fibre PMF.The periodic polarized crystal 6 is PPLN.Described
One hysteroscope CM1, the second hysteroscope CM2, third hysteroscope CM3, the 4th hysteroscope CM4 formation optical path are transmitted dish-like in hysteroscope medial surface
Chamber, the periodic polarized crystal 6 are arranged in the optical path between third hysteroscope CM3 and the 4th hysteroscope CM4.The thin metal gasket
4 one side of piece is attached on the end face of the output end of the second optical fiber 3, the spacing between opposite another side and collimator lens FC
For focusing distance f, the center of the first hysteroscope CM1 and the second hysteroscope CM2 line to collimator lens FC spacing is L12, described
Second optical fiber 3 transmission optical path successively after excessively thin metal gasket 4 and collimator lens FC from the first hysteroscope CM1 backwards to dish-like chamber
Face pass through the first hysteroscope CM1, then in turn through the second hysteroscope CM2 towards the medial surface back reflection in the middle part of dish-like chamber to third
Hysteroscope CM3 is towards the medial surface in the middle part of dish-like chamber and then is reflected into the 4th hysteroscope CM4 towards the medial surface in the middle part of dish-like chamber, again
Frequency light beam passes through the 4th hysteroscope CM4 and exports from from the lateral surface in the middle part of dish-like chamber, and the 4th hysteroscope CM4 is in the middle part of dish-like chamber
Lateral surface at be provided with dichroic mirror DM on output light path.
It is also disposed in optical path between the collimator lens FC and the first hysteroscope CM1 along the optical path direction of the launch
For adjusting the first reflecting mirror M1 and the second reflecting mirror M2 of optical path.First reflecting mirror M1 and the second reflecting mirror M2 is 1560nm
Total reflective mirror.
The first hysteroscope CM1 and the second hysteroscope CM2 is average chamber, and the third hysteroscope CM3 and the 4th hysteroscope CM4 are face
Medial surface in the middle part of to dish-like chamber is the flat-concave cavity of concave surface；Lateral surface of the first hysteroscope CM1 in the middle part of dish-like chamber is coated with
The anti-reflection film of 1560nm, the reflectance coating that it is T to the transmissivity of 1560nm that medial surface, which is coated with,；Second hysteroscope CM2 is towards in dish-like chamber
The medial surface in portion is coated with the film that is all-trans of 1560nm；The third hysteroscope CM3 and the 4th concave surface hysteroscope CM4 are setting curvature, curvature
Radius is 80mm, and third hysteroscope CM3 is coated with the film that is all-trans of 1560nm, the 4th hysteroscope in curved surface towards the medial surface in the middle part of dish-like chamber
CM4 is coated with the film that 1560nm is all-trans, 780nm high is saturating towards the medial surface in the middle part of dish-like chamber, the lateral surface in the middle part of dish-like chamber
It is coated with the anti-reflection film of 780nm；6 outer surface of periodic polarized crystal is coated with double anti-reflection films of 1560nm and 780nm.Periodical pole
Change 6 length of crystal is 20mm, and the distance between third hysteroscope CM3 and the 4th hysteroscope CM4 is 108mm, and the distance l between other hysteroscopes is
260mm.W with a tight waist between third hysteroscope CM3 and the 4th hysteroscope CM42Size is 66 μm, selects thin 4 thickness of metal gasket in this way
So that focusing distance f is that optimal pattern match can be realized in 450mm.
Double-frequency laser system including above-mentioned frequency multiplication light path module further includes laser 1, the first optical fiber 2, fiber electro-optic tune
Device EOM processed, EDFA Erbium-Doped Fiber Amplifier EDFA, servo circuit 7, quick coupling PD, piezoelectric ceramics PZT, the laser 1 pass through the
One optical fiber 2 is connect with the input terminal of fiber electro-optic modulator EOM, and the fiber electro-optic modulator EOM includes connecting with servo circuit 7
The first output end connect and the second output terminal being connect with EDFA Erbium-Doped Fiber Amplifier EDFA input terminal, the EDFA Erbium-Doped Fiber Amplifier
The output end of EDFA is connect with the input terminal of the second optical fiber 3, and lateral surface of the first hysteroscope CM1 in the middle part of dish-like chamber passes through
Quick coupling PD is connect with an input terminal of servo circuit 7, and the output end of the servo circuit 7 is connect with piezoelectric ceramics PZT, institute
Piezoelectric ceramics is stated to be arranged on the lateral surface of the second hysteroscope CM2.Wherein the first optical fiber 2 is also polarization maintaining optical fibre.
As shown in figure 3, the servo circuit 7 includes local oscillator LO, frequency mixer M, the low-pass filter set gradually
LP, proportional plus integral plus derivative controller PID, high-voltage amplifier HV, the first output end and local oscillation of fiber electro-optic modulator EOM
Device LO connection, the local oscillator LO and quick coupling PD are connect with the input terminal of frequency mixer M respectively, the low-pass filter
The output end of frequency mixer M is arranged in LP.
Herein by taking the double-frequency laser system of 780nm as an example, wherein laser 1 generates the seed laser of 1560nm, by the
After one optical fiber 2 enters fiber electro-optic modulator EOM modulation, output is used as frequency multiplication after input EDFA Erbium-Doped Fiber Amplifier EDFA amplification
Pumping laser.Laser of the pumping laser after the second optical fiber 3, collimator lens focusing is coupled into dish through reflecting mirror M1 and M2
In type chamber；Then frequency multiplication output is carried out by periodic polarized crystal 6.
Quickly probe PD is used to monitor the reflection spectrum signal of butterfly-type chamber, and believes with the modulation of fiber electro-optic modulator EOM
The error signal for locking chamber number is generated after frequency mixer M, low-pass filter LP, error signal is through PID control parameter
For controlling piezoelectric ceramics PZT after device PID, high-voltage amplifier HV amplification, for the locking of dish-like chamber.When dish-like chamber is in
Lock state, and when crystal temperature effect is in phase-matching condition, double-frequency laser output will be generated, double-frequency laser passes through double-colored
Mirror DM is separated with the fundamental frequency light of leakage.
In order to realize the extra cavity frequency-doubled laser output for realizing high efficiency and height mode quality with compact highly integrated optical path
Purpose, design includes the following steps.
(1) design completed determines the geometric dimension implementation pattern matching of butterfly chamber.
The end face of second optical fiber, 3 output end is to the optical path Center point between the first hysteroscope CM1 and the second hysteroscope CM2
Spread fiber matrix is expressed asF is the poly- of collimator lens FC in formula
Defocus distance, x are the thickness of thin metal gasket 4, and X is 0.2mm, A in this embodiment1、B1、C1、D1For the set of data in propogator matrix
Element；
The q parameter of second optical fiber, 3 output end endface is q0=iZ0=i π w02/λ；First hysteroscope CM1 and the second hysteroscope
The q parameter of CM2 is q1=iZ1=i π w12/λ；W0 is the core diameter of 3 end face of the second optical fiber, and w1 is dish-like the first intracavitary hysteroscope CM1
And the second waist radius size between hysteroscope CM2, i are imaginary unit, λ is the setting wavelength of frequency multiplication, Z0And Z1For Ruili distance；
The center of collimator lens FC to the first hysteroscope CM1 and the second hysteroscope CM2 line is set distance L12Coincidence formulaIn this embodiment, L12Value is 475mm.
From 6 center of periodic polarized crystal, can be expressed as in one week total abcd matrix of cavity circulationR is third hysteroscope CM3 and the 4th hysteroscope CM4 in formula
Radius of curvature, LcFor the length of crystal, l1For the distance of third hysteroscope CM3 and the 4th hysteroscope CM4, l is remaining hysteroscope spacing
From distance l is equal to one week total length of cavity circulation and subtracts the distance between third hysteroscope CM3 and the 4th hysteroscope CM4, and n is the period
The refractive index of property polarized crystal 6, A2、B2、C2、D2For the various element in propogator matrix；
Meeting condition | A2+D2| < 2, the waist radius size between third hysteroscope CM3 and the 4th hysteroscope CM4 isPresent invention selection | A+D | the situation of ≈ 0, at this moment the stability of dish-like chamber is best.
(2) it determines the filming parameter of each hysteroscope, realizes the impedance matching of frequency multiplication light path module.
(3) the optimal coefficient of coup is obtained
The Best Coupling coefficient of dish-like chamber isWherein PcIt is dish-like cavity circulation function
Rate, L are the intracavitary linear impairments other than input coupling hysteroscope；Γ is non-linear transfer coefficient, wherein Γ=ENL+Eabs；
ENLIt is the Clock Multiplier Factor in the case of once-through, EabsFor non-linear conversion absorption coefficient.Corresponding double frequency power isThe frequency doubled light of generation is by the part of absorption of crystal
In present example, efficient frequency multiplication output in order to obtain, the phase of the non-linear PPLN crystal of determination first
Position matching temperature can determine the phase matched temperature of crystal by measuring once-through double frequency power variation with temperature curve
Degree, for the temperature curve for the crystal in this example as shown in figure 4, best match temperature is 99 degrees Celsius, temperature bandwidth is 5
Degree.In order to characterize the parameter of butterfly chamber, we are firstly the need of the pattern match efficiency for seeing dish-like chamber.Pattern match efficiency can be from
The reflectance spectrum of dish-like chamber can calculate, and the ratio with the recess ratio of reflectance spectrum and the recess ratio of ideal situation is exactly mould
Formula matching efficiency, reflectance spectrum are as shown in Figure 5.It can be with come the matched efficiency of implementation pattern by the thickness using thin metal gasket 4
Reach 90% or so, effect is ideal.The use that lens group can be reduced in this way, greatly simplifies light channel structure.
To obtain stable frequency multiplication output, the resonant position by the stable lock of dish-like chamber in dish-like chamber, the present invention are needed
Example locks chamber technology using mature PDH, is loaded on fiber electro-optic modulator EOM using radio frequency source, gives one sideband of light field
It modulates, after the light field after sideband modulation is mixed low pass with the radiofrequency signal of modulation after dish-like cavity reflection is arrived by quick probe detection
The error signal of lock chamber is generated, error signal controls piezoelectric ceramics for locking chamber after the processing amplification of servo circuit 7.It is dish-like
Stable frequency multiplication output can be formed after chamber locking.
The final step of frequency multiplication optical path module design is the input cavity of characterization, shg efficiency and input power and dish-like chamber
The relationship of the mirror coefficient of coup.It is optimal there are one for given pump power it can be seen from Best Coupling coefficient formula
The coefficient of coup, the coefficient of coup depend on nonlinear loss caused by intracavitary linear impairments and frequency multiplication.Pump power is higher, coupling
It is bigger to close coefficient T.In service life polarized crystal 6, even if pump power is lower, also may be implemented to optimize turns
Change efficiency.Fig. 6 is pump power in present example, at coefficient of coup T=4.5% and transfer efficiency with pump power
Relationship.Frequency multiplication internal conversion efficiency reaches as high as being greater than 75%, and peak power is up to 430mW.
The above is only the preferred embodiments of the invention, are not intended to limit the invention creation, all in the present invention
Made any modifications, equivalent replacements, and improvements etc., should be included in the guarantor of the invention within the spirit and principle of creation
Within the scope of shield.
Claims (9)
1. a kind of frequency multiplication light path module, which is characterized in that including the second optical fiber (3), collimator lens FC, the thin gold for setting thickness
Belong to the week under gasket (4), the first hysteroscope CM1, the second hysteroscope CM2, third hysteroscope CM3, the 4th hysteroscope CM4, set temperature environment
Phase property polarized crystal (6), the first hysteroscope CM1, the second hysteroscope CM2, third hysteroscope CM3, the 4th hysteroscope CM4 form optical path and exist
The dish-like chamber of hysteroscope medial surface transmitting, the periodic polarized crystal (6) setting third hysteroscope CM3 and the 4th hysteroscope CM4 it
Between optical path on；On the end face for the output end that thin metal gasket (4) one side is attached to the second optical fiber (3), opposite is another
Spacing between side and collimator lens FC is focusing distance f, in the first hysteroscope CM1 and the second hysteroscope CM2 line
The heart and collimator lens FC spacing are L12, the optical path of the second optical fiber (3) transmission is successively through excessively thin metal gasket (4) and collimation
The first hysteroscope CM1 is passed through from the first hysteroscope CM1 backwards to the face of dish-like chamber after device lens FC, then in turn through the second hysteroscope CM2
Towards the medial surface back reflection in the middle part of dish-like chamber to third hysteroscope CM3 towards in the middle part of dish-like chamber medial surface, be then reflected into the
For four hysteroscope CM4 towards the medial surface in the middle part of dish-like chamber, frequency multiplication light beam passes through the 4th hysteroscope CM4 from the outside in the middle part of dish-like chamber
It is exported at face；
Light of the end face of second optical fiber (3) output end to the optical path Center point between the first hysteroscope CM1 and the second hysteroscope CM2
Fine propogator matrix is expressed asF is the focusing of collimator lens FC in formula
Distance, x are the thickness of thin metal gasket (4), A1、B1、C1、D1For the various element in propogator matrix；
The q parameter of the second optical fiber (3) output end endface is q0=iZ0=i π w02/λ；First hysteroscope CM1 and the second hysteroscope CM2
Q parameter be q1=iZ1=i π w12/λ；W0 is the core diameter of the second optical fiber (3) end face, and w1 is dish-like the first intracavitary hysteroscope CM1
And the second waist radius size between hysteroscope CM2, i are imaginary unit, λ is the setting wavelength of frequency multiplication, Z0And Z1For Ruili distance；
The center of first hysteroscope CM1 and the second hysteroscope CM2 line to collimator lens FC be set distance L12, L12Coincidence formula
It can be expressed as in one week total matrix of cavity circulationR is third hysteroscope CM3 and the 4th hysteroscope CM4 in formula
Radius of curvature, LcFor the length of crystal, l1For the distance of third hysteroscope CM3 and the 4th hysteroscope CM4, remaining chamber distance between mirrors is
L, distance l are equal to one week total length of cavity circulation and subtract the distance between third hysteroscope CM3 and the 4th hysteroscope CM4, and n is periodically
The refractive index of polarized crystal (6), A2、B2、C2、D2For the various element in propogator matrix；Meeting condition | A2+D2| < 2, third chamber
Waist radius size between mirror CM3 and the 4th hysteroscope CM4 is
2. a kind of frequency multiplication light path module according to claim 1, which is characterized in that the collimator lens FC and the first chamber
The first reflecting mirror M1 and second for adjusting optical path is also disposed with along the optical path direction of the launch in optical path between mirror CM1
Reflecting mirror M2.
3. a kind of frequency multiplication light path module according to claim 1, which is characterized in that the 4th hysteroscope CM4 is in dish-like chamber
Dichroic mirror DM is provided at the lateral surface in portion on output light path.
4. a kind of frequency multiplication light path module according to claim 1, which is characterized in that second optical fiber (3) is polarization-maintaining light
Fine PMF.
5. a kind of frequency multiplication light path module according to claim 1, which is characterized in that the periodic polarized crystal (6) is
PPLN。
6. a kind of frequency multiplication light path module according to claim 1, which is characterized in that the periodic polarized crystal (6) sets
It sets in temperature controlling stove (5), the temperature range of the temperature controlling stove (5) is 15-120 DEG C.
7. a kind of frequency multiplication light path module according to claim 1, which is characterized in that the first hysteroscope CM1 and the second chamber
Mirror CM2 is average chamber, and it is the flat of concave surface that the third hysteroscope CM3 and the 4th hysteroscope CM4, which are towards the medial surface in the middle part of dish-like chamber,
Cavity；Lateral surface of the first hysteroscope CM1 in the middle part of dish-like chamber is coated with the anti-reflection film of setting wavelength, and medial surface is coated with to this
The transmissivity of wavelength is the reflectance coating of T；Second hysteroscope CM2 is coated with the film that is all-trans of the wavelength towards the medial surface in the middle part of dish-like chamber；
The third hysteroscope CM3 and the 4th concave surface hysteroscope CM4 are setting curvature, and third hysteroscope CM3 is in the middle part of curved surface is towards dish-like chamber
Medial surface is coated with the film that is all-trans of the wavelength, the 4th hysteroscope CM4 towards the medial surface in the middle part of dish-like chamber be coated with the wavelength be all-trans, half-wave
The film to grow tall, the lateral surface in the middle part of dish-like chamber are coated with the anti-reflection film of half-wavelength；Periodic polarized crystal (6) outer surface is equal
Double anti-reflection films of the wavelength and half-wavelength are coated with, the Best Coupling coefficient of dish-like chamber isIts
Middle PcIt is dish-like cavity circulation power, L is the intracavitary linear impairments other than inputting dish-like chamber；Γ is non-linear transfer system
It counts, wherein Γ=ENL+Eabs；ENLIt is the Clock Multiplier Factor in the case of once-through, EabsFor non-linear conversion absorption coefficient.
8. a kind of double-frequency laser system including frequency multiplication light path module described in claim 1-7 any one, which is characterized in that
Further include laser (1), the first optical fiber (2), fiber electro-optic modulator EOM, EDFA Erbium-Doped Fiber Amplifier EDFA, servo circuit (7),
Quick coupling PD, piezoelectric ceramics PZT, the laser (1) pass through the input of the first optical fiber (2) and fiber electro-optic modulator EOM
End connection, the fiber electro-optic modulator EOM include the first output end connecting with servo circuit (7) and amplify with erbium-doped fiber
The second output terminal of device EDFA input terminal connection, the output end of the EDFA Erbium-Doped Fiber Amplifier EDFA are defeated with the second optical fiber (3)
Enter end connection, lateral surface of the first hysteroscope CM1 in the middle part of dish-like chamber passes through quick coupling PD and the one of servo circuit (7)
Input terminal connection, the output end of the servo circuit (7) are connect with piezoelectric ceramics PZT, and the piezoelectric ceramics is arranged in the second chamber
On the lateral surface of mirror CM2.
9. a kind of double-frequency laser system according to claim 8, which is characterized in that the servo circuit (7) includes the machine
Oscillator LO, frequency mixer M, the low-pass filter LP set gradually, proportional plus integral plus derivative controller PID, high-voltage amplifier HV, light
The first output end of fine electrooptic modulator EOM is connect with local oscillator LO, and the local oscillator LO and quick coupling PD divide
It is not connect with the input terminal of frequency mixer M, the output end of frequency mixer M is arranged in the low-pass filter LP.
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| CN104600552A (en) * | 2015-02-04 | 2015-05-06 | 厦门大学 | Monocrystalline-diamond continuous wave tunable deep ultraviolet laser |
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