CN114709707A - High-power sum frequency laser generation method and system and phase modulation method thereof - Google Patents
High-power sum frequency laser generation method and system and phase modulation method thereof Download PDFInfo
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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 thereof. The invention 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
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 of 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, single-frequency laser power improvement is limited by various nonlinear effects, particularly stimulated brillouin scattering, so that visible light and ultraviolet laser power is limited, wherein the stimulated brillouin scattering is abbreviated as SBS. 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 is generated in the high-power amplification process, the laser line width is further widened, and the line width characteristic of the sum frequency laser is influenced, wherein the four-wave mixing is called FWM for short. 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 realization method comprises the following steps that two single-frequency lasers output two single-frequency seed lasers, two driving signals are adopted to respectively carry out 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 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 the single-frequency laser output is obtained through the sum frequency of a nonlinear crystal,
wherein, the following formula is satisfied during phase modulation:
wherein,𝐸1、𝐸2for a single-frequency fundamental optical electric field strength,𝐸0representing the amplitude of the incident single-frequency fundamental light,𝛽1、𝛽2for phase modulation depth, phi1(t)、φ2(t) is a phase modulation function, f1(Ωt)、f2(Ω t) is an arbitrary function related to time, t is time,iin an imaginary unit, Ω is the frequency included in the phase modulation function, Φ is the phase difference generated by transmission amplification during the transmission of the two laser beams from phase modulation to sum frequency, 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 10 GHz, 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 above technical solutions, the present invention can also adopt or combine the following technical solutions:
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 10 kV, the bias is adjustable, and the frequency range of signals generated by the signal generator is 0-100 GHz 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 doubling, extraluminal resonance frequency doubling, single-pass frequency doubling, cascade single-pass frequency doubling and bi-pass frequency doubling;
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:
wherein,𝐸1、𝐸2for a single-frequency fundamental optical electric field strength,𝐸0representing the amplitude of the incident single-frequency fundamental light,𝛽1、𝛽2for phase modulation depth, phi1(t)、φ2(t) is a phase modulation function, f1(Ωt)、f2(Ω t) is an arbitrary function related to time, t is time,iin an imaginary unit, Ω is the frequency included in the phase modulation function, Φ is the phase difference generated by transmission amplification during the transmission of the two laser beams from phase modulation to sum frequency, and C is a constant.
The invention relates to a high-power sum frequency laser generating method, a high-power sum frequency laser generating system and a phase modulating method thereof.A single-frequency double-seed laser is subjected to phase modulation and amplification, the sum of phase modulation items between two amplified laser beams is constant, and high-power single-frequency sum frequency laser generation is obtained through laser sum frequency, wherein the sum frequency generation is called SFG for short; 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 thereof are suitable for sum frequency of any two single-frequency seed lasers, have wide application range, have the characteristics of simple structure, flexible modulation, high output power, good stability, low cost and the like, provide a new scheme of a high-power and 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 a parallel fiber laser amplifier 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 10 GHz 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 widths of the two single-frequency lasers, leading the two beams of lasers to enter a laser amplifier, simultaneously further adjusting the delay between the two signals, leading the two beams of lasers to enter a sum frequency device after passing through the laser amplifier, leading the sum of phase modulation terms of the lasers of the sum frequency in the sum frequency device to be a constant, and finally obtaining the single-frequency laser output by the sum frequency of a nonlinear crystal,
wherein, the following formula is satisfied during phase modulation:
wherein,𝐸1、𝐸2is the intensity of a single-frequency fundamental optical field,𝐸0representing the amplitude of the incident single-frequency fundamental light,𝛽1、𝛽2for phase modulation depth, phi1(t)、φ2(t) is a phase modulation function, f1(Ωt)、f2(Ω t) is an arbitrary function related to time, t is time,ithe frequency of the phase modulation function is the imaginary number unit, omega is the frequency contained in the phase modulation function, phi is the phase difference generated by the transmission amplification of the two laser beams in the transmission process from phase modulation to sum frequency, 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 amplitudes of the two signals are equal and the signs of the two signals are opposite, 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 utilizes two single-frequency lasers with the line width less than 10 GHz and the central wavelength difference not more than 6 microns to respectively apply two arbitrary signals with equal or close amplitude values to the two phase modulators through the two phase modulators, so that the line widths of the two single-frequency lasers are widened, the two beams of lasers enter a laser amplifier, meanwhile, the delay between the two signals is further adjusted, the sum of phase modulation items of the two beams of lasers in a sum frequency device is constant after the two beams of lasers pass through the amplifier, and finally, single-frequency laser output is obtained 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 the 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 commonly connected with the laser beam combining device 6.
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 10 kV and the bias is adjustable; the frequency range of the signal generated by the signal generator 3 is 0-100 GHz 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:
wherein,𝐸1、𝐸2for a single-frequency fundamental optical electric field strength,𝐸0representing the amplitude of the incident single-frequency fundamental light,𝛽1、𝛽2for phase modulation depth, phi1(t)、φ2(t) is a phase modulation function, f1(Ωt)、f2(Ω t) is an arbitrary function related to time, t is time,iin an imaginary unit, Ω is the frequency included in the phase modulation function, Φ is the phase difference generated by transmission amplification during the transmission of the two laser beams from phase modulation to sum frequency, 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 10 MHz 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 10 MHz 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 2 MHz 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 100 MHz, 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 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 the laser output by the laser amplification system 7 sequentially passes through the isolator 8. The laser beam combining device 6 employs a 2 × 2 50: 50 a beam splitter; the laser amplification system 7 is a cascade rare earth doped fiber laser amplifier, a gain fiber of the laser amplification system is an ytterbium-doped fiber, wherein 7.1 is a first-stage isolator, 7.2 is a first-stage ytterbium-doped fiber amplifier, 7.3 is a second-stage isolator, 7.4 is a second-stage ytterbium-doped fiber amplifier, 7.5 is a third-stage isolator, 7.6 is a third-stage ytterbium-doped fiber amplifier, and N = 2; the isolator 8 is a 1064 nm 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 used to perform phase modulation on two single frequency lasers with a line width less than 4 MHz, respectively, and spread spectrum to suppress 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 4 MHz 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 50 MHz, 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, and has high reflectivity at 1319nm and high transmittance at 1064 nm; 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 way primary isolator, 7.4 is a second way primary phosphorus-doped optical fiber Raman laser amplifier, 7.7 is a second way secondary isolator, 7.8 is a second way secondary phosphorus-doped optical fiber Raman laser amplifier, and N = 1; the isolator 8 is a space isolator, and comprises an isolator of 1064 nm 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 0.8 MHz 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 0.3 MHz, 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 0.8 MHz 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 150 MHz, the output amplitude is 8V, the phase between the signals is fixed to pi-pi/2, and the MgO-doped LN first phase modulator 4 and the MgO-doped LN second phase modulator 5 are respectively driven, wherein the pi/2 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 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 which is ytterbium-doped yttrium aluminum garnet Yb: YAG crystal, wherein 7.1 is a primary isolator, 7.2 is a primary Yb: YAG amplifier, 7.3 is a secondary isolator, 7.4 is a secondary Yb: YAG amplifier, 7.5 is a tertiary isolator, 7.6 is a tertiary Yb: YAG amplifier, and N = 2; the isolator 8 is a 1064 nm 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 8 MHz are respectively subjected to phase modulation, and the spectrum is spread to inhibit the SBS effect in the amplification process; 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; 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 smaller than 8 MHz, and a central wavelength 1064.1 nm; the second single-frequency laser 2 is a single-frequency Raman fiber laser with the line width of 2 MHz 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 2 Gbps, an output amplitude of 7V, and a time delay between signals fixed at 910 ps, 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-channel first-level isolator, 7.4 is a second-channel first-level ytterbium-doped optical fiber amplifier, 7.7 is a second-channel second-level isolator, 7.8 is a second-channel second-level ytterbium-doped optical fiber amplifier, 7.11 is a second-channel third-level isolator, 7.15 is a second-channel third-level ytterbium-doped optical fiber amplifier, and N = 2; the isolator 8 is a space isolator, and comprises an isolator of 1064 nm 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 27The time delay of the pseudo-random signal of-1 is fixed to 910 ps, 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 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 23Pseudo-random signal of-1, two single-frequency lasers with line width less than 1 MHz are respectively subjected to phase modulation, and spectrum is expanded to inhibit SBS effect in the amplification processThe preparation method comprises the following steps of; 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 0.5 MHz 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 1 MHz 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 1.71 Gbps, 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 =1 at this time; the isolator 8 is a 1550 nm 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 1550 nm high reflection and temperature control devices thereof, 9.3 is an 777.5 nm spectroscope, and 9.4 is a sum frequency light collimating lens.
In the high power sum frequency laser generation system of this embodiment, two are 23The time delay of the pseudo-random signal of-1 is fixed to 800 ps, 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-described embodiments are intended 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 realization method is as follows, the output angular frequency of two single-frequency lasers is omega1And ω2The two single-frequency seed lasers adopt two driving signals with the respective diagonal frequency of omega1And omega2The two single-frequency lasers are subjected to phase modulation, arbitrary signals with equal amplitude and opposite signs are applied to the two seed lasers by the phase modulation at the same time, the line widths of the two single-frequency lasers are widened, the two beams of lasers enter a laser amplifier, meanwhile, 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 terms 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 phase modulation satisfies the formula:
wherein,𝐸1、𝐸2is the intensity of a single-frequency fundamental optical field,𝐸0representing the amplitude of the incident single-frequency fundamental light,𝛽1、𝛽2for phase modulation depth, phi1(t)、φ2(t) is a phase modulation function, f1(Ωt)、f2(Ω t) is an arbitrary function related to time, t is time,iin an imaginary unit, Ω is the frequency included in the phase modulation function, Φ is the phase difference generated by transmission amplification during the transmission of the two laser beams from phase modulation to sum frequency, 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 10 GHz, 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 10 kV, the bias is adjustable, and the frequency range of the signal generated by the signal generator is 0-100 GHz 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 wave signal, a square wave signal or a pulse signal; a pseudo-random code signal, and a signal having an amplitude that varies in a step-over-time fashion.
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 beams of lasers is constant;
wherein, the following formula is satisfied during phase modulation:
wherein,𝐸1、𝐸2for a single-frequency fundamental optical electric field strength,𝐸0representing the amplitude of the incident single-frequency fundamental light,𝛽1、𝛽2for phase modulation depth, phi1(t)、φ2(t) is a phase modulation function, f1(Ωt)、f2(Ω t) is an arbitrary function related to time, t is time,iin an imaginary unit, Ω is the frequency included in the phase modulation function, Φ is the phase difference generated by transmission amplification during the transmission of the two laser beams from phase modulation to sum frequency, and C is a constant.
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| CN114614331A (en) | 2022-06-10 |
| CN114709707B (en) | 2022-09-13 |
| WO2023103630A1 (en) | 2023-06-15 |
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