CN114614331A - High-power sum frequency laser generation method and system and phase modulation method used by same - Google Patents

High-power sum frequency laser generation method and system and phase modulation method used by same Download PDF

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CN114614331A
CN114614331A CN202111499566.XA CN202111499566A CN114614331A CN 114614331 A CN114614331 A CN 114614331A CN 202111499566 A CN202111499566 A CN 202111499566A CN 114614331 A CN114614331 A CN 114614331A
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laser
frequency
phase modulation
sum
sum frequency
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冯衍
曾鑫
林治全
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Hangzhou Institute of Advanced Studies of UCAS
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Hangzhou Institute of Advanced Studies of UCAS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • 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
    • H01S3/10053—Phase control
    • 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
    • G02F1/35—Non-linear optics
    • G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
    • 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
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0092—Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2383—Parallel arrangements
    • H—ELECTRICITY
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    • 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
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0085—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for modulating the output, i.e. the laser beam is modulated outside the laser 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
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0092—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser 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
    • 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
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4012—Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms

Abstract

The invention discloses a high-power sum frequency laser generating method, a high-power sum frequency laser generating system and a phase modulation method used by the high-power sum frequency laser generating method, wherein two single-frequency seed lasers output by two single-frequency lasers and output by the two single-frequency lasers, two driving signals are adopted to respectively perform phase modulation on the two single-frequency lasers, the phase modulation simultaneously applies arbitrary signals with equal amplitude and opposite signs to the two seed lasers, so that the line widths of the two single-frequency lasers are widened, two beams of lasers enter a laser amplifier, the delay between the two signals is further adjusted simultaneously, and the single-frequency laser output is obtained through nonlinear crystal sum frequency after the sum frequency. The single-frequency visible laser device has the advantages of wide wavelength range, simple and compact structure, flexible design, low cost and the like, can effectively break through the power limitation of the traditional single-frequency visible laser technology, provides a new technical scheme for the high-power and high-stability single-frequency visible laser technology, and has important practical value and application prospect.

Description

High-power sum frequency laser generation method and system and phase modulation method used by same
Technical Field
The invention relates to the technical field of laser, in particular to a high-power sum frequency laser generation method, a high-power sum frequency laser generation system and a phase modulation method used by the high-power sum frequency laser generation system.
Background
The infrared laser can effectively expand the wavelength range of the laser through a second-order nonlinear process, such as frequency multiplication, sum frequency, optical parametric oscillation and the like, and the output of visible light and ultraviolet laser is realized. Visible light and ultraviolet band lasers have important applications in the fields of laser display, metal processing, quantum information technology, laser remote sensing and detection, medical imaging and treatment, cold atom and the like. Laser sum frequency technology is an effective way to obtain high power visible and ultraviolet lasers. In practical application, high-efficiency sum frequency conversion efficiency and high-power sum frequency laser output are realized, two beams of high-power single-frequency laser pumping are needed, and single-frequency laser power boosting is limited by various nonlinear effects, particularly Stimulated Brillouin Scattering (SBS), so that visible light and ultraviolet laser power is limited. The phase modulation technique is widely applied to power improvement of high-power single-frequency and narrow-linewidth fiber lasers due to a plurality of advantages.
However, in the phase modulation process, the line width of the single-frequency laser is widened and then amplified, so that the narrow line width characteristic of the laser is damaged to a certain extent, the line width of the sum frequency laser is further influenced, and the high-power single-frequency or narrow line width sum frequency laser cannot be obtained. The small-frequency laser formed by combining a plurality of single-frequency lasers can also inhibit SBS in the amplification process, but because the single-frequency lasers have no fixed phase relation, four-wave mixing (FWM) and the like are generated in the high-power amplification process, the laser line width is further widened, and the line width characteristic of sum frequency laser is influenced. The spectrum compression technology based on phase modulation and frequency multiplication can effectively solve the problem of low output power of single-frequency visible light and ultraviolet laser, however, the frequency multiplication scheme needs step type signals such as square waves or pseudo-random codes to perform phase modulation with fixed modulation depth, generates frequency multiplication laser with high demodulation rate, generally needs high-quality signals, is often higher in cost, and is limited in SBS suppression capability.
Therefore, how to avoid influencing the line width of the sum frequency laser in the phase modulation process, and solve the problem of low output power of the visible light and the ultraviolet laser with single frequency or narrow line width, and generating the laser with high spectral intensity and narrow line width is a technical problem to be solved urgently by the technical staff in the field.
Disclosure of Invention
The first purpose of the present invention is to provide a high power sum frequency laser generation method, which aims at the problem of low output power of single frequency or narrow linewidth visible light or ultraviolet laser in the prior art.
Therefore, the above purpose of the invention is realized by the following technical scheme:
a high power sum frequency laser generation method, characterized by: the method comprises the following steps that two single-frequency lasers output two single-frequency seed lasers, two driving signals are adopted to carry out phase modulation on the two single-frequency lasers respectively, arbitrary signals with equal amplitude and opposite signs are applied to the two seed lasers by the phase modulation simultaneously, the line width of the two single-frequency lasers is widened, the nonlinear effect is improved, two beams of lasers enter a laser amplifier, the delay between the two signals is further adjusted, the two beams of lasers enter a sum frequency device after passing through the laser amplifier, the sum of phase modulation items of the sum frequency lasers in the sum frequency device is a constant, and finally single-frequency laser output is obtained by the sum frequency of a nonlinear crystal, wherein the following formula is met during the phase modulation:
Figure BDA0003402219540000021
Figure BDA0003402219540000022
Figure BDA0003402219540000023
Figure BDA0003402219540000024
wherein E isi＝1，2For a single-frequency fundamental optical field intensity, E0Representing the amplitude, beta, of incident monochromatic fundamental lighti＝1，2In order to modulate the depth of the phase,
Figure BDA0003402219540000025
as a function of phase modulation, fi＝1，2And (omega t) is an arbitrary function related to time, omega is the angular frequency of the laser, omega is the frequency contained in the phase modulation function, phi is the phase difference of the two laser beams in the transmission process from phase modulation to sum frequency due to transmission amplification, and C is a constant.
While adopting the technical scheme, the invention can also adopt or combine the following technical scheme:
as a preferred technical scheme of the invention: the driving signal is two signals, when the driving signal is periodic sine wave, cosine wave, square wave or triangular wave, the phase difference of the two signals is in the range of [ n pi-phi-pi/4, n pi + phi + pi/4 ], n is an odd number, phi is the phase difference generated by transmission amplification of the two laser beams in the transmission process from phase modulation to sum frequency, the driving signal compensates the phase difference, and the sum of phase modulation terms of the two laser beams with sum frequency is constant.
As a preferred technical scheme of the invention: the driving signals are two signals, when the driving signals are periodic pulses, pseudo-random signals or other arbitrary signals, the amplitudes of the two signals are equal, the signs of the two signals are opposite, the time delay between the two driving signals is adjusted, and the sum of the phase modulation terms of the two beams of laser with sum frequency is constant.
A second object of the present invention is to provide a high power sum frequency laser generating system, which overcomes the disadvantages of the prior art.
Therefore, the above purpose of the invention is realized by the following technical scheme:
a high-power sum frequency laser generation system comprises a first single-frequency laser, a second single-frequency laser, a signal generator, a first phase modulator, a second phase modulator, a sum frequency laser amplification system and a laser sum frequency device, wherein the line width of the first single-frequency laser is less than 10GHz, and the center wavelength difference is not more than 6 microns; the two driving signals generated by the signal generator respectively drive the first phase modulator and the second phase modulator to perform phase modulation on the two single-frequency lasers, and then the two single-frequency lasers are amplified and combined by the sum frequency laser amplification system, so that the nonlinear effect is improved, and finally the sum of the phase modulation terms of the two laser beams entering the laser sum frequency device is constant, and single-frequency sum frequency laser output is obtained.
While adopting the technical scheme, the invention can also adopt or combine the following technical scheme:
as a preferred technical scheme of the invention: the sum frequency laser amplification system comprises a laser beam combining device, a laser amplification system and an isolator; the laser beam combining device selects an optical fiber laser beam splitter or coupler with a tail fiber, a laser beam splitter, a dichroic mirror, a polarization beam splitter or a laser beam combiner or a wavelength division multiplexer; one end of the laser beam combining device is connected with the first phase modulator and the second phase modulator together, the other end of the laser beam combining device is connected with the laser amplification system, and laser output by the laser amplification system passes through the isolator;
or the first phase modulator and the second phase modulator are respectively connected with the laser amplification system, and the laser amplification systems are jointly connected with the laser beam combining device and then pass through the isolator;
or the first phase modulator and the second phase modulator are respectively connected with the laser amplification system, and the laser amplification system is connected with the isolator and then is commonly connected with the laser beam combining device.
As a preferred technical scheme of the invention: the signal generator is a signal generator with adjustable signal amplitude, the peak value is not more than 10kV, the bias is adjustable, and the frequency range of signals generated by the signal generator is 0-100GHz or the code rate is 0-500 Gbps;
the signal generator can generate a plurality of signals, and the phases or time delays among the signals can be mutually locked and adjusted;
the driving signal sent by the signal generator is a periodic signal or an aperiodic arbitrary signal, and the periodic signal comprises a sine signal, a cosine signal, a triangular wave signal, a square wave signal, a pulse signal and the like; the pseudo-random code signal is a signal with the amplitude value changing along with the time step type.
As a preferred technical scheme of the invention: the first phase modulator and the second phase modulator are electro-optic phase modulators with fiber tails or space electro-optic phase modulators, and the modulation depth and the frequency interval of the phase modulation laser are changed by the output amplitude, the frequency or the code rate adjusted by the signal generator.
As a preferred technical scheme of the invention: the laser amplification system comprises a one-stage or multi-stage rare earth doped solid amplifier, a solid Raman amplifier, a rare earth doped optical fiber amplifier and an optical fiber Raman amplifier which are connected in parallel or in cascade.
As a preferred technical scheme of the invention: the sum frequency device adopts intracavity frequency multiplication, extracavity resonance frequency multiplication, single-pass frequency multiplication, cascade single-pass frequency multiplication and double-pass frequency multiplication;
the sum frequency crystal in the sum frequency device is selected from the following components: periodically poled lithium niobate, periodically poled lithium niobate doped with magnesium oxide, periodically poled stoichiometric ratio lithium tantalate doped with magnesium oxide, periodically poled potassium titanyl phosphate crystals, periodically poled potassium titanyl arsenate, potassium dihydrogen phosphate, potassium dideuterium phosphate, beta-barium metaborate crystals, lithium triborate crystals, bismuth borate crystals, lithium cesium borate crystals, or potassium titanyl phosphate crystals.
A third objective of the present invention is to provide a phase modulation method, which overcomes the drawbacks of the prior art.
Therefore, the above purpose of the invention is realized by the following technical scheme:
the invention discloses a phase modulation method applied to laser sum frequency technology, which is characterized in that: two driving signals are adopted to respectively carry out phase modulation on the two single-frequency lasers, and the modulated lasers are amplified; during phase modulation, any signals with equal amplitude and opposite signs are applied to the two seed lasers, and the sum of phase modulation terms of the two amplified lasers is constant; wherein, the following formula is satisfied during phase modulation:
Figure BDA0003402219540000051
Figure BDA0003402219540000052
Figure BDA0003402219540000053
Figure BDA0003402219540000054
wherein E isi＝1，2For a single-frequency fundamental optical field intensity, E0Representing the amplitude, beta, of incident monochromatic fundamental lighti＝1，2In order to modulate the depth of the phase,
Figure BDA0003402219540000055
as a function of phase modulation, fi＝1，2And (omega t) is an arbitrary function related to time, omega is the angular frequency of the laser, omega is the frequency contained in the phase modulation function, phi is the phase difference of the two laser beams in the transmission process from phase modulation to sum frequency due to transmission amplification, and C is a constant.
The invention relates to a high-power sum frequency laser generating method and a system and a phase modulation method used by the high-power sum frequency laser generating method and system, which modulate and amplify single-frequency double-seed laser phases, ensure that the sum of phase modulation items between two amplified laser beams is constant, obtain high-power single-frequency SFG through laser sum frequency, adopt single-frequency laser phase modulation of sum frequency of two arbitrary signal pairs, ensure that the sum of phase modulation items of the two laser beams in a sum frequency device is constant, obtain single-frequency SFG through the sum frequency process, avoid the broadening of the line width of the sum frequency laser caused by SBS, and keep the line width characteristic of the sum frequency of the single-frequency laser before phase modulation; according to the high-power sum frequency laser generation method and the phase modulation method adopted by the high-power sum frequency laser generation method, the phase modulation of the single-frequency laser for sum frequency is carried out by adopting two arbitrary signals, so that the complexity of the device can be avoided, and the system cost is reduced; the invention can change the modulation depth, frequency interval and phase or delay between signals of the phase modulation laser by adjusting the amplitude, frequency and phase of the signal generator, not only can flexibly reduce the power spectral density of the single-frequency laser so as to better inhibit SBS, but also can flexibly and effectively adjust the phase delay of the two beams of laser in the sum frequency device so as to obtain the single-frequency SFG. The high-power sum frequency laser generating method and the phase modulation method used by the same are suitable for sum frequency of any two single-frequency seed lasers, are wide in application range, have the characteristics of simple structure, flexibility in modulation, high output power, good stability, low cost and the like, provide a new scheme of a high-power high-stability single-frequency laser sum frequency technology, and have important practical value and wide application prospect.
Drawings
FIG. 1 is a schematic diagram of a high power sum frequency laser generating device provided by the present invention;
FIG. 2 is a schematic structural diagram a of a sum frequency laser amplification system provided by the present invention;
fig. 3 is a schematic structural diagram b of a sum frequency laser amplification system provided by the invention;
fig. 4 is a schematic structural diagram c of a sum frequency laser amplification system provided by the invention;
FIG. 5 is a schematic diagram of a cascaded erbium-doped fiber laser amplifier according to the present invention;
FIG. 6 is a schematic diagram of a configuration of fiber laser amplifiers provided in parallel according to the present invention;
fig. 7 is a schematic structural diagram of a sum frequency device provided by the present invention;
in the drawings:
a first single frequency laser 1; a second single frequency laser 2; a signal generator 3; a first phase modulator 4; a second phase modulator 5; a laser beam combining device 6; the laser amplification system 7, 7.1 is a first-stage isolator, 7.2 is a first-stage amplifier, 7.3 is a second-stage isolator, 7.4 is a second-stage amplifier, 7.5 is a third-stage isolator, and 7.6 is a third-stage amplifier; an isolator 8; a laser sum frequency device 9; 9.1 is an optical focusing lens, 9.2 is a sum frequency crystal and a temperature control device thereof, 9.3 is a spectroscope, and 9.4 is a collimating lens; and a sum frequency laser amplification system 10.
Detailed Description
The invention is described in further detail with reference to the figures and specific embodiments.
The invention relates to a high-power sum frequency laser generating method, which comprises the following steps of selecting two single-frequency lasers with the line width less than 10GHz and the central wavelength difference not more than 6 microns to output two single-frequency seed lasers, adopting two driving signals to respectively carry out phase modulation on the two single-frequency lasers, simultaneously applying arbitrary signals with equal amplitude and opposite signs to the two seed lasers by the phase modulation to widen the line width of the two single-frequency lasers and enable the two beams of lasers to enter a laser amplifier, simultaneously further adjusting the delay between the two signals, enabling the two beams of lasers to enter a sum frequency device after passing through the laser amplifier, enabling the sum of phase modulation terms of the sum frequency lasers in the sum frequency device to be a constant, and finally obtaining single-frequency laser output through nonlinear crystal sum frequency,
wherein, the following formula is satisfied during phase modulation:
Figure BDA0003402219540000071
Figure BDA0003402219540000072
Figure BDA0003402219540000073
Figure BDA0003402219540000074
wherein E isi＝1，2For a single-frequency fundamental optical field intensity, E0Indicating incident monochromaticAmplitude of fundamental light, betai＝1，2In order to modulate the depth of the phase,
Figure BDA0003402219540000075
as a function of phase modulation, fi＝1，2The (Ω t) is an arbitrary function related to time, ω is the angular frequency of the laser, Ω is the frequency contained in the phase modulation function, φ is the phase difference between the two laser beams during the transmission from phase modulation to sum frequency due to transmission amplification, and C is a constant.
In the invention, two arbitrary driving signals with equal amplitude and opposite sign are adopted to respectively modulate the phase of two beams of single-frequency laser, so that the sum of the phase modulation terms of the two beams of laser in sum frequency is a constant, thereby obtaining single-frequency sum frequency laser output. Two driving signals are adopted to respectively carry out phase modulation on two single-frequency lasers, and the two single-frequency lasers are used for inhibiting nonlinear effects such as stimulated Brillouin scattering and the like in the laser amplification process; further adjusting the delay between the two driving signals, so that after phase modulation and amplification, the sum of phase modulation terms of the two laser beams subjected to sum frequency is a constant, and finally obtaining single-frequency laser through a sum frequency process; wherein, two drive signals of phase modulation are arbitrary signals, satisfy the condition: the two driving signals have equal amplitude and opposite signs, the two driving signals have equal amplitude including being completely equal or nearly equal, and when the two beams of laser after phase modulation sum frequency, the sum of phase modulation terms of the two beams of laser is constant.
When the driving signal is two periodic sine waves, cosine waves, square waves or triangular waves, the phase difference of the two signals is in the range of [ n pi-phi-pi/4, n pi + phi + pi/4 ], n is an odd number, phi is the phase difference generated by transmission amplification and the like in the transmission process of phase modulation to sum frequency of the two laser beams, and the sum of the phase modulation terms of the two laser beams with the sum frequency is constant by compensating the phase.
When the driving signals are two periodic pulses, pseudo-random signals or other arbitrary signals, the two signals have equal amplitudes and opposite signs, and the sum of two laser phase modulation terms for sum frequency is constant by adjusting the time delay between the two signals, so that single-frequency sum frequency laser output is obtained.
The invention relates to a high-power sum frequency laser generating method, which comprises the steps of utilizing two single-frequency lasers with line widths smaller than 10GHz and central wavelength difference smaller than or equal to 6 microns to respectively apply two arbitrary signals with equal or close amplitudes to the two phase modulators through the two phase modulators, widening the line widths of the two single-frequency lasers, enabling the two beams of lasers to enter a laser amplifier, simultaneously further adjusting the delay between the two signals, enabling the sum of phase modulation terms of the two beams of lasers to be constant in a sum frequency device after the two beams of lasers pass through the amplifier, and finally obtaining single-frequency laser output through nonlinear crystal sum frequency.
The phase modulation in the invention has the characteristics of wide wavelength range and flexible adjustment, the modulation process can effectively inhibit the stimulated Brillouin scattering in laser amplification and obtain high-power laser, and simultaneously, single-frequency and sum-frequency laser output can be obtained by adjusting the delay between two signals, thereby realizing the preparation of high-power and high-stability single-frequency or narrow-linewidth visible laser.
The invention discloses a high-power sum frequency laser generating system, which comprises: the laser frequency summation device comprises a first single-frequency laser 1, a second single-frequency laser 2, a signal generator 3, a first phase modulator 4, a second phase modulator 5, a summation frequency laser amplification system 10 and a laser summation frequency device 9.
The first single-frequency laser 1 and the second single-frequency laser 2 are respectively connected with the first phase modulator 4 and the second phase modulator 5, and the first phase modulator 4 and the second phase modulator 5 are further connected with the sum frequency laser amplification system 10 and the laser sum frequency device 9 together; the two signals generated by the signal generator 3 respectively drive the first phase modulator 4 and the second phase modulator 5, so that the sum of phase modulation terms on the two laser beams passing through the first phase modulator 4 and the second phase modulator 5, and then passing through the sum frequency laser amplification system 10 for amplification and beam combination, and finally entering the laser sum frequency device 9 is constant, thereby obtaining single-frequency sum frequency laser output.
The sum frequency laser amplification system 10 includes: the device comprises a laser beam combining device 6, a laser amplification system 7 and an isolator 8; the connection mode of the sum frequency laser amplification system 10 may be as follows: one end of the laser beam combining device 6 is connected with the first phase modulator 4 and the second phase modulator 5 together, the other end of the laser beam combining device is connected with the laser amplification system 7, and laser output by the laser amplification system 7 sequentially passes through the isolator 8; the connection mode of the sum frequency laser amplification system 10 may also be: the first phase modulator 4 and the second phase modulator 5 are respectively connected with the laser amplification system 7. The laser amplification systems 7 are connected with the laser beam combining device 6 together and then sequentially pass through the isolator 8; or the laser amplification system 7 is connected with the isolator 8 and then is connected with the laser beam combining device 6 together.
The first single-frequency laser 1 and the second single-frequency laser 2 can be rare earth doped solid lasers, solid raman lasers, distributed feedback DFB semiconductor lasers, external cavity semiconductor ECDL lasers, distributed feedback DFB fiber lasers or distributed bragg reflection DBR fiber lasers or other lasers or any combination of the above lasers, and the linewidths of the generated single-frequency lasers are all less than 10 GHz; the difference of the central wavelengths of the first single-frequency laser 1 and the second single-frequency laser 2 is not more than 6 microns.
The signal generator 3 is a periodic signal, including a sine signal, a cosine signal, a triangular signal, a square signal, a pulse signal and the like; pseudo-random code signal constant amplitude is along with the signal of the step type change of time; and other arbitrary signals.
The signal generator 3 can generate a plurality of signals, and the phases or time delays among the signals can be locked with each other or adjusted; the amplitude of the signal generated by the signal generator 3 is adjustable, and the peak-to-peak value is not more than 10kV and the bias is adjustable; the frequency range of the signal generated by the signal generator 3 is 0-100GHz or the code rate is 0-500 Gbps; the modulation depth and frequency interval of the phase modulated laser can be changed by adjusting the output amplitude, frequency or code rate of the signal generator 3.
The first phase modulator 4 and the second phase modulator 5 are electro-optic phase modulators with fiber tails or space electro-optic phase modulators, and are driven by the generator 3; the output ends of the first phase modulator 4 and the second phase modulator 5 are connected with a sum frequency laser amplification system 10.
The laser beam combining device 6 is a device with a laser beam combining function, such as an optical fiber laser beam splitter (or coupler) with a tail fiber, a laser beam splitter, a dichroic mirror, a polarization beam splitter, a laser beam combiner or a Wavelength Division Multiplexer (WDM).
The laser amplification system 7 comprises a one-stage or multi-stage rare earth doped solid amplifier, a solid Raman amplifier, a rare earth doped optical fiber amplifier, an optical fiber Raman amplifier and the like which are connected in parallel or in cascade, and the parallel connection or cascade combination of the laser amplifiers.
The sum frequency device 9 adopts intracavity frequency doubling, extracavity resonance frequency doubling, single-pass frequency doubling, cascade single-pass frequency doubling, double-pass frequency doubling and the like.
The sum frequency crystal in the sum frequency device is periodically polarized lithium niobate PPLN, periodically polarized lithium niobate MgO doped with magnesium oxide PPLN, periodically polarized lithium tantalate MgO doped with magnesium oxide PPSLT, periodically polarized potassium titanyl phosphate crystal PPKTP, periodically polarized potassium titanyl arsenate PPKTA, potassium titanyl arsenate KTA, potassium dihydrogen phosphate (KDP), potassium dideuterium phosphate (DKDP), beta-barium metaborate crystal BBO, lithium triborate crystal LBO, bismuth borate crystal BIBO, lithium cesium borate crystal CLBO or potassium titanyl phosphate crystal KTP.
The invention discloses a phase modulation method, which is applied to a laser sum frequency technology, and is characterized in that two driving signals are adopted to respectively carry out phase modulation on two single-frequency lasers and amplify the modulated lasers; during phase modulation, any signals with equal amplitude and opposite signs are applied to the two seed lasers, and the sum of phase modulation terms of the two amplified lasers is constant;
wherein, the following formula is satisfied during phase modulation:
Figure BDA0003402219540000101
Figure BDA0003402219540000102
Figure BDA0003402219540000103
Figure BDA0003402219540000104
wherein E isi＝1，2For a single-frequency fundamental optical field intensity, E0Representing the amplitude, beta, of incident monochromatic fundamental lighti＝1，2In order to modulate the depth of the phase,
Figure BDA0003402219540000105
as a function of phase modulation, fi＝1，2And (omega t) is an arbitrary function related to time, omega is the angular frequency of the laser, omega is the frequency contained in the phase modulation function, phi is the phase difference of the two laser beams in the transmission process from phase modulation to sum frequency due to transmission amplification, and C is a constant.
Example 1
As shown in fig. 1, fig. 2, fig. 5, and fig. 7, in the method for generating high power sum frequency laser according to the present invention, two sinusoidal signals are adopted, two single frequency lasers with a line width smaller than 10MHz are subjected to sinusoidal phase modulation, a spectrum is spread to suppress the SBS effect during amplification, two laser beams after phase modulation enter a cascaded laser amplifier together to be amplified through laser beam combination, the amplified laser beams pass through an isolator and are subjected to single pass sum frequency, and the phase difference of the two sinusoidal phase modulation signals is adjusted to obtain the high power single frequency sum frequency laser.
The high-power sum frequency laser generation system in the embodiment comprises a first single frequency laser 1 which is a single frequency distribution feedback semiconductor laser with a line width of 10MHz and has a central wavelength of 1064 nm; the second single-frequency laser 2 is a single-frequency distribution feedback DFB fiber laser with the line width of 2MHz and the central wavelength of 1064.5 nm; the signal generator 3 adopts an arbitrary wave signal source to generate two sinusoidal signals, the frequency is 100MHz, the output amplitude is 6V, the phase between the signals is fixed to pi-pi/5, and the MgO-doped LN first phase modulator 4 and the MgO-doped LN second phase modulator 5 are respectively driven, wherein the pi/5 is the phase difference between two beams of laser in the transmission and amplification process. The sum frequency laser amplification system 10 is connected as follows: one end of the laser beam combining device 6 is commonly connected with the first phase modulator 4 and the second phase modulator 5, the other end of the laser beam combining device is connected with the laser amplification system 7, and laser output by the laser amplification system 7 sequentially passes through the isolator 8. The laser beam combining device 6 adopts a 2 x 2 50: 50 a beam splitter; the laser amplification system 7 is a cascaded rare earth doped fiber laser amplifier, a gain fiber of the laser amplification system is a ytterbium-doped fiber, wherein 7.1 is a primary isolator, 7.2 is a primary ytterbium-doped fiber amplifier, 7.3 is a secondary isolator, 7.4 is a secondary ytterbium-doped fiber amplifier, 7.5 is a tertiary isolator, 7.6 is a tertiary ytterbium-doped fiber amplifier, and N is 2 at the moment; the isolator 8 is a 1064nm space isolator; the laser sum frequency device 9 is a single pass sum frequency structure, 9.1 is an optical focusing lens, 9.2 is a sum frequency crystal PPSLT and a temperature control device thereof, 9.3 is a spectroscope, and 9.4 is a collimating lens.
In the high-power sum frequency laser generating system in this embodiment, the phase difference between the two sinusoidal signals is pi/5, the sum of the phase modulation terms of the two laser beams in the sum frequency device is 0, and the central wavelength of the output laser beam is 532.125 nm.
Example 2
As shown in fig. 1, fig. 3, fig. 6, and fig. 7, in the method for generating high power sum frequency laser according to the present invention, two square wave signals are adopted, two single frequency lasers with a line width less than 4MHz are respectively phase-modulated, and a spectrum is spread to suppress the SBS effect during amplification; the two laser beams are respectively amplified through two laser amplifiers connected in parallel, and the amplified laser beams finally pass through the laser combination together through an isolator and are subjected to single pass and sum frequency; and the phase difference of the two square wave signals is adjusted, so that high-power single-frequency and sum-frequency laser is obtained. The high-power sum-frequency laser generation system in the embodiment comprises a first single-frequency laser 1, a second single-frequency laser 1, a third single-frequency laser, a fourth single-frequency laser, a fifth single-frequency laser, a sixth single-frequency laser, a fifth single-frequency laser, a sixth single-frequency laser, a fifth single-frequency laser, a sixth single-frequency laser, a fourth single-frequency laser, a third single-frequency laser, a fourth single-frequency laser, a fourth single-frequency, a third single-frequency laser, a fourth single-frequency, a third, a fourth, a, in this embodiment, a, in this embodiment, a, the first, the, a, the, in this, the; the second single-frequency laser 2 is a single-frequency distribution feedback DFB fiber laser with the line width of 4MHz and the central wavelength of 1319 nm; the signal generator 3 adopts an arbitrary wave signal source to generate two square wave signals, the frequency is 50MHz, the output amplitude is 8V, the phase between the signals is fixed to pi-pi/8, and an MgO-doped SLT first phase modulator 4 and an MgO SLT second phase modulator 5 are respectively driven, wherein the pi/8 is the phase difference between two beams of laser in the transmission and amplification process. The connection mode of the sum frequency laser amplification system 10 is as follows: the first phase modulator 4 and the second phase modulator 5 are respectively connected with the laser amplification system 7, and the laser amplification system 7 is commonly connected with the laser beam combining device 6 and then sequentially passes through the isolator 8. The laser beam combining device 6 adopts a 45-degree dichroic mirror to achieve 1319nm high reflection and 1064nm high transmission; the laser amplification system 7 is a parallel structure of a first path of ytterbium-doped rare-earth optical fiber laser amplifier and a second path of phosphorus-doped optical fiber Raman laser amplifier, wherein 7.1 is a first path of primary isolator, 7.2 is a first path of primary ytterbium-doped optical fiber amplifier, 7.5 is a first path of secondary isolator, and 7.6 is a first path of secondary ytterbium-doped optical fiber amplifier; 7.3 is a second path of primary isolator, 7.4 is a second path of primary phosphorus-doped optical fiber Raman laser amplifier, 7.7 is a second path of secondary isolator, 7.8 is a second path of secondary phosphorus-doped optical fiber Raman laser amplifier, and N is 1 at the moment; the isolator 8 is a space isolator, and comprises an isolator of 1064nm and an isolator of 1319 nm; the laser sum frequency device 9 is a cascade single pass sum frequency structure, 9.1 is an optical focusing lens, 9.2 comprises two sum frequency crystals LBO, a focusing lens and a temperature control device, 9.3 is a spectroscope, and 9.4 is a collimating lens.
In the high-power sum frequency laser generating system in this embodiment, the phase difference between the two square wave signals is pi/8, the sum of the phase modulation terms of the two laser beams in the sum frequency device is 0, and the central wavelength of the output laser beam is 588.928 nm.
Example 3:
as shown in fig. 1, fig. 2, fig. 5, and fig. 7, in the method for generating high power sum frequency laser according to the present invention, two triangular wave signals are adopted, two single frequency lasers with a linewidth less than 0.8MHz are respectively phase-modulated, and a spectrum is spread to suppress the SBS effect during amplification; combining two beams of laser through lasers, carrying out cascade laser amplification, amplifying the two beams of laser, and finally carrying out single-pass sum frequency by the amplified laser respectively through an isolator; and the high-power single-frequency and sum-frequency laser is obtained by adjusting the time delay of the two triangular wave signals.
In this embodiment, a high power sum frequency laser generating system includes a first single frequency laser 1 which is a distributed bragg reflection DBR single frequency fiber laser with a line width of 0.3MHz, and has a central wavelength of 1063.5 nm; the second single-frequency laser 2 is a single-frequency distribution feedback DFB fiber laser with the line width of 0.8MHz and the central wavelength of 1064.5 nm; the signal generator 3 adopts an arbitrary wave signal source to generate two triangular wave signals, the frequency is 150MHz, the output amplitude is 8V, the phase between the signals is fixed to pi-pi/2, and the signals respectively drive an LN first phase modulator 4 doped with MgO and an LN second phase modulator 5 doped with MgO, wherein the pi/2 is the phase difference between two beams of laser in the transmission and amplification processes. The sum frequency laser amplification system 10 is connected as follows: one end of the laser beam combining device 6 is commonly connected with the first phase modulator 4 and the second phase modulator 5, the other end of the laser beam combining device is connected with the laser amplification system 7, and laser output by the laser amplification system 7 sequentially passes through the isolator 8. The laser beam combining device adopts a 2 x 2 40: 60 a beam splitter; the laser amplification system 7 is a cascaded rare earth doped solid laser amplifier, the gain of the laser amplification system is ytterbium-doped yttrium aluminum garnet Yb: YAG crystal, wherein 7.1 is a first-stage isolator, 7.2 is a first-stage Yb: YAG amplifier, 7.3 is a second-stage isolator, 7.4 is a second-stage Yb: YAG amplifier, 7.5 is a third-stage isolator, 7.6 is a third-stage Yb: YAG amplifier, and N is equal to 2; the isolator 8 is a 1064nm space isolator; the sum frequency device 9 is a single pass sum frequency structure, 9.1 is an optical focusing lens, 9.2 is a sum frequency crystal PPLN and a temperature control device thereof, 9.3 is a spectroscope, and 9.4 is a collimating lens.
In the high-power sum frequency laser generating system in the embodiment, the phase difference between the two square wave signals is pi/2, the phase modulation terms of the two laser beams in the sum frequency device are about 0, and the central wavelength of the output laser is 532 nm.
Example 4:
as shown in fig. 1, 4, 6 and 7, the high power sum frequency laser generation method of the present invention adopts two laser beams 27The pseudo-random signal of-1, two single-frequency lasers with the line width less than 8MHz are respectively subjected to phase modulation, and the spectrum is spread to inhibit the SBS effect in the amplification process; two laser amplifiers connected in parallel are used for amplifying and amplifying two beams of laser respectivelyThe two laser beams are subjected to single pass and sum frequency by passing through the isolators respectively and finally combining the laser beams together; by regulating two paths 27-1, thereby obtaining high power single frequency and frequency laser light.
In this embodiment, a high power sum frequency laser generating system includes a first single frequency laser 1 which is a distributed bragg reflection DBR single frequency fiber laser with a line width less than 8MHz and has a center wavelength of 1064.1 nm; the second single-frequency laser 2 is a single-frequency Raman fiber laser with the line width of 2MHz and the central wavelength of 1319.2 nm; the signal generator 3 is a pseudo-random code signal source and generates two paths 27A pseudo-random signal of-1, a pseudo code rate of 2Gbps, an output amplitude of 7V, and a time delay between signals fixed at 910ps, to drive the MgO-doped LN first phase modulator 4 and the MgO-doped LN second phase modulator 5, respectively. The connection mode of the sum frequency laser amplification system 10 is as follows: the first phase modulator 4 and the second phase modulator 5 are respectively connected with the laser amplification system 7, and the laser amplification system 7 is respectively connected with the laser beam combining device 6 through the isolator 8. The laser amplification system 7 is a first path of rare earth doped fiber laser amplifier and a second path of quartz fiber Raman laser which are connected in parallel, gain fibers of the laser amplification system are ytterbium-doped fibers and passive quartz fibers respectively, wherein 7.1 is a first path of primary isolator, 7.2 is a first path of primary ytterbium-doped fiber amplifier, 7.5 is a first path of secondary isolator, 7.6 is a first path of secondary ytterbium-doped fiber amplifier, 7.9 is a first path of tertiary isolator, and 7.10 is a first path of tertiary ytterbium-doped fiber amplifier; 7.3 is a second-path first-level isolator, 7.4 is a second-path first-level ytterbium-doped optical fiber amplifier, 7.7 is a second-path second-level isolator, 7.8 is a second-path second-level ytterbium-doped optical fiber amplifier, 7.11 is a second-path third-level isolator, 7.15 is a second-path third-level ytterbium-doped optical fiber amplifier, and at this time, N is 2; the isolator 8 is a space isolator, and comprises an isolator of 1064nm and an isolator of 1319 nm; the sum frequency device 9 is a single pass sum frequency structure, 9.1 is an optical focusing lens, 9.2 is a sum frequency crystal LBO and a temperature control device thereof, 9.3 is a spectroscope, and 9.4 is a collimating lens.
In the high power sum frequency laser generating system of the present embodiment, two are 27Time delay of pseudo-random signal of-1 is fixed to 910ps, two beamsThe phase modulation term of the laser in the sum frequency device is about 0, and the central wavelength of the output laser is 589 nm.
Example 5:
as shown in fig. 1, 2, 6 and 7, the high power sum frequency laser generation method of the present invention adopts two laser beams 231, respectively carrying out phase modulation on two single-frequency lasers with the line width smaller than 1MHz, and expanding the spectrum to inhibit the SBS effect in the amplification process; combining two beams of laser through lasers, carrying out cascade laser amplification, amplifying the two beams of laser, and finally carrying out single-pass sum frequency by the amplified laser respectively through an isolator; by regulating two paths 23-1, thereby obtaining high power single frequency and frequency laser light.
The high-power sum frequency laser generation system in the embodiment comprises a first single-frequency laser 1, a second single-frequency laser 2, a third single-frequency laser, a fourth single-frequency laser, a fifth single-frequency laser and a sixth single-frequency laser, wherein the first single-frequency laser 1 is a single-frequency external cavity semiconductor ECDL laser with the line width smaller than 0.5MHz and has the central wavelength of 1560nm, and the second single-frequency laser is a single-frequency external cavity semiconductor ECDL laser with the line width of 1MHz and has the central wavelength of 1550 nm; the signal generator 3 is a pseudo-random code signal source and generates two paths 23A pseudo-random signal of-1, a pseudo code rate of 1.71Gbps, an output amplitude of 10V, and a time delay between signals fixed at 800 ps. The sum frequency laser amplification system 10 is connected as follows: one end of the laser beam combining device 6 is commonly connected with the first phase modulator 4 and the second phase modulator 5, the other end of the laser beam combining device is connected with the laser amplification system 7, and laser output by the laser amplification system 7 sequentially passes through the isolator 8. A laser beam combining device, which adopts a 2 x 2 50: 50 a fiber coupler; the laser amplification system 7 is a cascaded erbium-doped fiber laser amplifier, a gain fiber of the laser amplification system is an erbium-doped fiber, wherein 7.1 is a first-level fiber isolator, 7.2 is a first-level erbium-doped fiber amplifier, 7.3 is a second-level fiber isolator, 7.4 is a second-level erbium-doped fiber amplifier, and N is 1; the isolator 8 is a 1550nm space isolator; the sum frequency device 9 is a double-pass sum frequency structure, 9.1 is an optical focusing lens, 9.2 comprises a sum frequency crystal PPLN, a concave total reflection mirror pair 1560nm and 1550nm high reflection and temperature control devices thereof, 9.3 is an 777.5nm spectroscope, and 9.4 is a sum frequency light collimating lens.
High power sum frequency laser of this embodimentIn the raw system, two are 23The time delay of the pseudo-random signal of-1 is fixed to 800ps, the phase modulation terms of the two lasers in the sum frequency device are about 0, and the central wavelength of the output laser is 777.492 nm.
According to the method and the system for generating the high-power sum frequency laser, the single-frequency double-seed laser of the sum frequency is modulated and amplified in phase, high-power output is realized, and the high-power single-frequency laser is further obtained through the sum frequency process; the phase modulation applies arbitrary signals with equal amplitude and opposite signs to the two seed lasers simultaneously, and the sum of the phase modulation terms is constant in the sum frequency process, so that the power limitation of the traditional single-frequency visible laser technology is effectively broken through, and the high-power and high-stability single-frequency and high-frequency visible laser output is realized.
The above detailed description is provided to illustrate the present invention, but not to limit the present invention, and any modifications, equivalents, improvements, etc. made within the spirit of the present invention and the scope of the claims fall within the scope of the present invention.

Claims (10)

1. A high power sum frequency laser generation method, characterized by: the method comprises the following steps that two single-frequency lasers output two single-frequency seed lasers, the two single-frequency lasers output two single-frequency seed lasers, two driving signals are adopted to carry out phase modulation on the two single-frequency lasers respectively, arbitrary signals with equal amplitude and opposite signs are applied to the two seed lasers by the phase modulation simultaneously, the line width of the two single-frequency lasers is widened, the two laser beams enter a laser amplifier, meanwhile, the delay between the two signals is further adjusted, the two laser beams enter a sum frequency device after passing through the laser amplifier, the sum of phase modulation items of the sum frequency laser in the sum frequency device is a constant, and finally, the single-frequency laser output is obtained by the sum frequency of a nonlinear crystal,
wherein the phase modulation satisfies the formula:
Figure FDA0003402219530000011
Figure FDA0003402219530000012
Figure FDA0003402219530000013
Figure FDA0003402219530000014
β2＝β1
wherein E isi＝1，2For a single-frequency fundamental optical field intensity, E0Representing the amplitude, beta, of incident monochromatic fundamental lighti＝1，2In order to modulate the depth of the phase,
Figure FDA0003402219530000015
as a function of phase modulation, fi＝1，2The (Ω t) is an arbitrary function related to time, ω is the angular frequency of the laser, Ω is the frequency contained in the phase modulation function, φ is the phase difference between the two laser beams during the transmission from phase modulation to sum frequency due to transmission amplification, and C is a constant.
2. The high power sum frequency laser generating method of claim 1, wherein: the driving signal is two signals, when the driving signal is a periodic sine wave, a periodic cosine wave, a periodic square wave or a periodic triangular wave, the phase difference of the two signals is in the range of [ n pi-phi-pi/4, n pi + phi + pi/4 ], n is an odd number, phi is the phase difference generated by transmission amplification of the two laser beams in the transmission process from phase modulation to sum frequency, and the driving signal is adjusted to compensate the phase difference so as to realize that the sum of phase modulation terms of the two laser beams for sum frequency is constant.
3. The high power sum frequency laser generating method of claim 1, wherein: the driving signals are two signals, when the driving signals are periodic pulses, pseudo-random signals or other arbitrary signals, the amplitudes of the two signals are equal, the signs of the two signals are opposite, and the time delay between the two driving signals is adjusted, so that the sum of phase modulation terms of the two beams of laser used for sum frequency is constant after phase modulation and amplification.
4. High power and sum frequency laser generating system using the method of any of claims 1-3, characterized by: the system comprises a first single-frequency laser, a second single-frequency laser, a signal generator, a first phase modulator, a second phase modulator, a sum frequency laser amplification system and a laser sum frequency device, wherein the line width of the first single-frequency laser and the line width of the second single-frequency laser are less than 10GHz, and the central wavelength difference is not more than 6 micrometers; the two driving signals generated by the signal generator respectively drive the first phase modulator and the second phase modulator to perform phase modulation on the two single-frequency lasers, so that the nonlinear effect in the amplification process is improved, the two single-frequency lasers are amplified and combined by the sum frequency laser amplification system, and finally the sum of the phase modulation terms of the two laser beams entering the laser sum frequency device is constant, and single-frequency sum frequency laser output is obtained.
5. The high power sum frequency laser generating system of claim 4, wherein: the sum frequency laser amplification system comprises a laser beam combining device, a laser amplification system and an isolator;
one end of the laser beam combining device is connected with the first phase modulator and the second phase modulator together, the other end of the laser beam combining device is connected with the laser amplification system, and laser output by the laser amplification system passes through the isolator;
or the first phase modulator and the second phase modulator are respectively connected with the laser amplification system, and the laser amplification systems are jointly connected with the laser beam combining device and then pass through the isolator;
or, the first phase modulator and the second phase modulator are respectively connected with the laser amplification system, the laser amplification system is connected with the isolator and then is commonly connected with the laser beam combining device or the laser beam combining device selects an optical fiber laser beam splitter or coupler with a tail fiber, a laser beam splitter, a dichroic mirror, a polarization beam splitter or a laser beam combiner or a wavelength division multiplexer.
6. The high power sum frequency laser generating system of claim 4, wherein: the signal generator is a signal generator with adjustable signal amplitude, the peak value is not more than 10kV, the bias is adjustable, and the frequency range of signals generated by the signal generator is 0-100GHz or the code rate is 0-500 Gbps; the signal generator can generate a plurality of signals, and the phases or time delays among the signals can be mutually locked and adjusted;
the driving signal sent by the signal generator is a periodic signal or an aperiodic arbitrary signal, and the periodic signal is a sine signal, a cosine signal, a triangular signal, a square signal, a pulse signal and the like; the pseudo-random code signal is a signal with the amplitude value changing along with the time step type.
7. The high power sum frequency laser generating system of claim 4, wherein: the first phase modulator and the second phase modulator are electro-optic phase modulators with fiber tails or space electro-optic phase modulators, and the modulation depth, the phase and the frequency interval of the phase modulation laser are respectively changed by the output amplitude, the time delay, the frequency or the code rate adjusted by the signal generator.
8. The high power sum frequency laser generating system of claim 4, wherein: the laser amplification system comprises a one-stage or multi-stage rare earth doped solid amplifier, a solid Raman amplifier, a rare earth doped optical fiber amplifier and an optical fiber Raman amplifier which are connected in parallel or in cascade.
9. The high power sum frequency laser generating system of claim 4, wherein: the sum frequency device adopts intracavity frequency multiplication, extracavity resonance frequency multiplication, single-pass frequency multiplication, cascade single-pass frequency multiplication and double-pass frequency multiplication;
the sum frequency crystal in the sum frequency device is selected from the following components: periodically poled lithium niobate, periodically poled lithium niobate doped with magnesium oxide, periodically poled stoichiometric ratio lithium tantalate doped with magnesium oxide, periodically poled potassium titanyl phosphate crystals, periodically poled potassium titanyl arsenate, potassium dihydrogen phosphate, potassium dideuterium phosphate, beta-barium metaborate crystals, lithium triborate crystals, bismuth borate crystals, lithium cesium borate crystals, or potassium titanyl phosphate crystals.
10. A phase modulation method is applied to laser sum frequency technology, and is characterized in that: two driving signals are adopted to respectively carry out phase modulation on the two single-frequency lasers, and the modulated lasers are amplified; during phase modulation, any signals with equal amplitude and opposite signs are applied to the two seed lasers, and the sum of phase modulation terms of the two amplified lasers is constant;
wherein, the following formula is satisfied during phase modulation:
Figure FDA0003402219530000031
Figure FDA0003402219530000032
Figure FDA0003402219530000033
Figure FDA0003402219530000034
β2＝β1
wherein E isi＝1，2For a single-frequency fundamental optical field intensity, E0Representing the amplitude, beta, of incident monochromatic fundamental lighti＝1，2In order to modulate the depth of the phase,
Figure FDA0003402219530000035
as a function of phase modulation, fi＝1，2(Ω t) is an arbitrary function related to timeOmega is the angular frequency of the laser, omega is the frequency contained in the phase modulation function, phi is the phase difference generated by the transmission amplification of the two beams of laser in the transmission process from phase modulation to sum frequency, and C is a constant.
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Application publication date: 20220610

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