CN114927921A - Femtosecond laser harmonic generation system based on coherent beam combination - Google Patents

Femtosecond laser harmonic generation system based on coherent beam combination Download PDF

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CN114927921A
CN114927921A CN202210370906.7A CN202210370906A CN114927921A CN 114927921 A CN114927921 A CN 114927921A CN 202210370906 A CN202210370906 A CN 202210370906A CN 114927921 A CN114927921 A CN 114927921A
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pulse
femtosecond
laser
harmonic generation
mode
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毕根毓
储玉喜
刘博文
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Georgia Institute Of Technology Tianjin University Shenzhen
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Georgia Institute Of Technology Tianjin University Shenzhen
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—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
    • H01S3/0057—Temporal shaping, e.g. pulse compression, frequency chirping
    • 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
    • H01S3/0071—Beam steering, e.g. whereby a mirror outside the cavity is present to change the beam direction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers
    • 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
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094076—Pulsed or modulated pumping

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  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)

Abstract

The invention relates to the technical field of femtosecond laser, and provides a femtosecond laser harmonic generation system based on coherent beam combination, which reduces the power load on a single crystal and solves the problem of limited harmonic laser power lifting; wherein: the femtosecond pulse seed source is used for generating a femtosecond pulse sequence with certain power, and the output end of the femtosecond pulse seed source is connected with the pulse stretcher; the pulse stretcher is used for stretching the pulse width of the output pulse of the seed source, and the output end of the pulse stretcher is connected with the pulse beam splitter. The invention is mainly applied to the occasion of generating femtosecond laser harmonic waves.

Description

Femtosecond laser harmonic generation system based on coherent beam combination
Technical Field
The invention relates to the technical field of femtosecond laser, in particular to an optical system of a femtosecond laser harmonic generator based on a coherent beam combination technology.
Background
The femtosecond laser has the characteristics of short pulse duration and high peak power, has unique advantages in the aspects of fast process detection, special material processing, interaction of light and substances and the like, and is more and more widely applied to the fields of scientific research, industrial processing, biomedical treatment and the like. The development and application of the femtosecond laser technology are rapidly popularized and deepened, and higher requirements are put forward on the power aspect of green light and ultraviolet femtosecond laser with higher single photon energy. At present, the generation and amplification of femtosecond laser are all in near-infrared wave band, although harmonic waves of green light, ultraviolet and other near-infrared femtosecond laser can be obtained by utilizing nonlinear frequency conversion technology, the further improvement of the power of the green light and ultraviolet femtosecond laser and the further popularization and application of the femtosecond laser are hindered due to the limitations of damage threshold of nonlinear crystal, crystal damage caused by long-time work and the like.
The laser coherent beam combination technology can coherently combine laser beams output by a plurality of amplifiers from the same seed source into one laser beam. The phase of the laser output by each amplification channel is actively controlled to be consistent through a feedback loop, and high-efficiency coherent beam combination can be realized. The technique is capable of achieving high power output beyond the maximum output power limit of a single laser amplifier while maintaining beam quality. Coherent synthesis techniques are mainly divided into two modes, i.e., a filled aperture and a tiled aperture, according to the synthesis mode, wherein the filled aperture is more suitable for synthesis with a large number of channels but has lower synthesis efficiency, and the tiled aperture requires a certain synthesis element such as a partial mirror but has higher efficiency. For coherent beam combination of a continuous light laser, because the coherent time is long, the phases of the laser output by the multi-path amplification channels are consistent, and the requirement on multi-path optical path difference is wide. For coherent beam combination of femtosecond pulse laser, in addition to maintaining phase consistency, the consistency of optical path difference, dispersion and the like among different channels needs to be controlled, so that the phases of femtosecond pulses of different amplification channels are kept as consistent as possible in the whole spectral range, and high-efficiency coherent beam combination can be obtained. The optical fiber laser amplification system has good beam quality, high consistency of multi-channel amplification results and good heat dissipation, so that the coherent synthesis technology commonly uses the optical fiber laser amplification system as a discrete amplification channel.
Femtosecond laser of green light and ultraviolet bands is mainly generated by nonlinear frequency conversion (second harmonic generation and higher harmonic generation) technology. The generation of high-power harmonic waves is mainly influenced by the heat absorption in the nonlinear crystal in the harmonic generation process, even if the crystal is cooled, a large temperature gradient is generated, the phenomena of output light spot degradation, conversion efficiency reduction and the like are caused, even the crystal is damaged, and strong ultraviolet laser can also cause the gradual degradation of the emergent surface and an anti-reflection film of the nonlinear crystal. Therefore, only the power of the fundamental frequency light is increased, and the coherent and combined high-power laser is used for frequency conversion to obtain harmonic laser, so that an upper power limit exists, and the generation of the high-power harmonic laser is limited.
The power boost of single channel based harmonic generation systems can be affected by thermal effects, while there are practical demands for high power harmonic laser systems, e.g. for extreme ultraviolet generation, medicine, processing fields, etc. Therefore, an effective solution is needed to break through the power limitation of the laser harmonic generation system.
Disclosure of Invention
Aiming at overcoming the defects of the prior art, the problems that in the existing high-power harmonic generation based on a single-channel nonlinear crystal, the thermal absorption causes the output harmonic laser facula deterioration, the phase mismatch causes the reduction of the conversion efficiency, and the harmonic power promotion caused by the crystal damage threshold is limited. The invention aims to provide a femtosecond laser harmonic generation system based on coherent beam combination, which reduces the power load on a single crystal and solves the problem of limited power improvement of harmonic laser. Therefore, the invention adopts the technical scheme that the femtosecond laser harmonic generation system based on coherent beam combination comprises a femtosecond pulse seed source, a pulse stretcher, a pulse beam splitter, an optical fiber amplifier, a pulse compressor, a laser harmonic generator, a pulse beam combiner and an electric control loop; wherein:
the femtosecond pulse seed source is used for generating a femtosecond pulse sequence with certain power, adopts a structure of an oscillator and power pre-amplification, and the output end of the femtosecond pulse seed source is connected with a pulse stretcher;
the pulse stretcher is used for stretching the pulse width of the pulse output by the seed source and amplifying the subsequent chirped pulse, and the output end of the pulse stretcher is connected with the pulse beam splitter;
the pulse beam splitter is used for spatially dividing the broadened pulses into multiple paths and is respectively connected with the corresponding optical fiber amplifiers;
the optical fiber amplifier is used for amplifying chirped pulses of the multi-channel expanded pulses to realize power boosting, and the outputs of the optical fiber amplifier are respectively connected with corresponding pulse compressors;
the pulse compressor is used for compressing the pulse width of the amplified pulse to the narrowest value, is matched with the pulse stretcher, improves the peak power and further improves the conversion efficiency in the harmonic generation process, and the output of the pulse compressor is respectively connected with the corresponding laser harmonic generator;
the laser harmonic generator is used for respectively realizing the phase matching process of the compressed multiple pulses in the multi-channel nonlinear crystal to generate harmonic waves, and the output of the laser harmonic generator is connected with the pulse beam combiner;
the pulse beam combiner is used for spatially combining a plurality of harmonic laser beams into one beam, and the combined beam is detected by the photoelectric detector and then is connected with the electric control loop;
the electric control loop is used for controlling the phases of a plurality of harmonic laser beams to be consistent, so that high-efficiency coherent combination is realized.
The mode locking mode of the femtosecond pulse seed source oscillator can be nonlinear polarization rotation, a saturable absorber and a nonlinear amplification ring mirror.
The stretcher is a single-mode fiber or a Bragg body grating; the beam splitter is any one of a half-mirror, a polarizing beam splitter and a thin film polarizer.
The optical fiber used by the amplifier is a large mode field area double-clad optical fiber, a photonic crystal optical fiber or a rod-shaped optical fiber.
The pulse compressor can be one or more of a grating pair, a Bragg body grating, a prism pair and a chirped mirror; the nonlinear crystal is one of lithium triborate, barium metaborate, potassium titanyl phosphate and periodically poled lithium niobate.
The beam combination mode is selected to fill the aperture to obtain high synthesis efficiency, and the beam combiner can be a half-transmitting and half-reflecting mirror, a polarization beam splitter or a thin film polarizer.
And (3) beam combination is carried out by using a semi-transparent semi-reflective mirror, the electric control loop carries out phase locking by adopting a single detector frequency marking mode or a random parallel gradient descent mode, and if the polarization beam combination is used, the electric control loop carries out phase locking by adopting a Hansch-Couillaud technology.
The invention has the characteristics and beneficial effects that:
the invention reduces the power load on a single crystal by performing harmonic generation respectively after femtosecond laser beam splitting amplification and respective compression, thereby maintaining high beam quality and high conversion efficiency. The light after the harmonic generation is respectively carried out is subjected to coherent beam combination by using a semi-transparent semi-reflective mirror through a synthesis mode of filling an aperture, so that the problem of limited power improvement of harmonic laser is solved.
1. Because the high-power fundamental frequency light after multi-channel amplification is subjected to harmonic generation and then coherent synthesis, the heat load of a single crystal caused by the fact that the fundamental frequency light is subjected to coherent synthesis and then harmonic generation in the traditional mode is relieved, and therefore the power improvement limit caused by light spot degradation, efficiency reduction and crystal damage in the high-power harmonic generation process can be eliminated.
2. The system has strong expansibility, and can continuously increase the output power of the harmonic laser of the system without being limited by a crystal damage threshold value and the like by increasing the number of channels of the optical fiber amplifier and the laser harmonic generator.
3. The system is not limited to generation of second harmonic, and the higher harmonic generation process can also improve harmonic output power by respectively generating harmonic waves and then performing coherent synthesis in the mode, and particularly relates to the situation that ultraviolet strong absorption and an antireflection film are easy to damage.
Description of the drawings:
fig. 1 is a schematic diagram of a basic structure of a two-channel femtosecond laser second harmonic coherent synthesis system according to the present invention.
In the figure: 1. 3 optical fiber collimator, 2 single mode optical fiber, 4, 10, 25 half wave plate, 5, 40 non-polarization beam splitting cube, 6, 22 polarization beam splitting cube, 7, 23 quarter wave plate, 8 piezoelectric ceramic driving mirror, 9 forty-five degree reflector, 11, 13, 15, 19, 21, 26, 28, 30, 34, 36 convex lens, 12, 27 large mode field area ytterbium doped optical fiber, 14, 17, 29, 32 dichroic mirror, 18, 33 grating pair based pulse compressor, 20, 35 nonlinear crystal LBO, 37, 38 filter, 39 piezoelectric deflection mirror, 41 sampler, 42 light barrier, 43 four quadrant detector.
Detailed Description
The invention provides a femtosecond laser harmonic generator coherent beam combining device, which comprises a femtosecond pulse seed source, a pulse stretcher, a pulse beam splitter, an optical fiber amplifier, a pulse compressor, a laser harmonic generator, a pulse beam combiner and an electric control loop, wherein the femtosecond pulse seed source is connected with the pulse stretcher, the pulse beam splitter and the optical fiber amplifier; wherein:
the femtosecond pulse seed source is used for generating a femtosecond pulse sequence with certain power, adopts a structure of an oscillator and power pre-amplification, and the output end of the femtosecond pulse seed source is connected with a pulse stretcher; the mode locking mode of the oscillator can be nonlinear polarization rotation, a saturable absorber, a nonlinear amplification ring mirror and the like;
the pulse stretcher is used for stretching the pulse width of the pulse output by the seed source and amplifying the subsequent chirped pulse, and the output end of the pulse stretcher is connected with the pulse beam splitter; the stretcher can be a single-mode fiber, a Bragg body grating and the like;
the pulse beam splitter is used for spatially dividing the broadened pulses into multiple paths and is respectively connected with the corresponding optical fiber amplifiers; the beam splitter can be a semi-transparent semi-reflecting mirror, a polarization beam splitter, a thin film polarizer and the like;
the optical fiber amplifier is used for amplifying chirped pulses of the multi-channel expanded pulses to realize power boosting, and the outputs of the optical fiber amplifier are respectively connected with corresponding pulse compressors; the optical fiber used by the amplifier can be a large mode field area double-clad optical fiber, a photonic crystal optical fiber, a rod-shaped optical fiber and the like;
the pulse compressor is used for compressing the pulse width of the amplified pulse to be the narrowest, is matched with the pulse stretcher, improves the peak power and further improves the conversion efficiency in the harmonic generation process, and the output of the pulse compressor is respectively connected with the corresponding laser harmonic generator; the pulse compressor can be one or more of a grating pair, a Bragg body grating, a prism pair and a chirped mirror;
the laser harmonic generator is used for respectively realizing the phase matching process of the compressed multiple pulses in the multi-channel nonlinear crystal to generate harmonic waves, and the output of the laser harmonic generator is connected with the pulse beam combiner; the nonlinear crystal can be lithium triborate (LBO), barium metaborate (BBO), potassium titanyl phosphate (KTP), Periodically Poled Lithium Niobate (PPLN), etc.;
the pulse beam combiner is used for spatially combining a plurality of harmonic laser beams into one beam, and the combined beam is detected by the photoelectric detector and then is connected with the electric control loop; the beam combination mode is selected as a filling aperture to obtain high synthesis efficiency, and the beam combiner can be a semi-transparent and semi-reflective mirror, a polarization beam splitter, a thin film polarizer and the like;
the electric control loop is used for controlling the phases of a plurality of harmonic lasers to be consistent, so that high-efficiency coherent synthesis is realized; the beam combining is carried out by using a semi-transparent semi-reflecting mirror, the phase locking can be carried out on the electric control loop in a single detector frequency mark (LOCSET) mode or a random parallel gradient descent (SPGD) mode, the phase locking can be carried out on the electric control loop by using a Hansch-Couillaud technology by using polarization beam combining;
the present invention will be further described by way of specific examples, which are provided to illustrate the structure of the femtosecond laser harmonic generator coherent synthesis system according to the present invention and are intended to be illustrative in more detail and should not be construed as limiting the invention.
As shown in fig. 1, a femtosecond laser second harmonic coherent combining system includes: a femtosecond pulse seed source, a pulse stretcher, a pulse beam splitter, a fiber amplifier, a pulse compressor, a laser harmonic generator, a pulse beam combiner and an electric control loop.
The femtosecond pulse seed source adopts a structure of an ytterbium-doped fiber femtosecond oscillator and power pre-amplification, a mode locking mechanism is nonlinear polarization rotation and is used for transmitting a femtosecond pulse sequence with certain power, and the central wavelength is about 1040 nm;
the pulse stretcher adopts a polarization-maintaining single-mode fiber and is used for stretching pulses to perform subsequent chirped pulse amplification so as to reduce the influence of nonlinear effect; the part comprises fiber collimators 1 and 3 for coupling and collimating laser, a single-mode fiber 2 for providing a positive dispersion time domain broadening pulse, and a half-wave plate 3 for adjusting the polarization state of the laser emitted by a polarization-maintaining fiber;
the pulse beam splitter adopts a non-polarization beam splitting cube 5 and is used for splitting a single beam of pulse into two beams of pulses with the same power, wherein one beam of pulse channel is added with a combination of a polarization beam splitting cube 6, a quarter-wave plate 7 and a piezoelectric ceramic driving mirror 8 for phase active control, 9 is a 45-degree reflector, and the other beam of pulse channel is added with a combination of a polarization beam splitting cube 22, a quarter-wave plate 23 and a 0-degree reflector 24 arranged on a displacement platform and is used for group delay adjustment;
the optical fiber amplifier adopts two large-mode-area double-cladding polarization-maintaining ytterbium-doped optical fibers with equal length as a gain medium, and further comprises half-wave plates 10 and 25 for adjusting the polarization state of incident pulses; lenses 11, 13, 15, 26, 28 and 30 are used for coupling and collimating laser light; the dichroic mirrors 14, 17, 29 and 32 are highly transparent to the pump light and highly reflective to the seed light, and are used for extracting amplified laser light; semiconductor lasers 16 and 31 with a center wavelength of 976nm are used as pump sources for the fiber amplifiers. The amplification effects of the two-channel optical fiber amplifiers are kept consistent as much as possible, and the coherent combination efficiency is improved;
the pulse compressors 18 and 33 adopt two pairs of gratings with the same parameters, the detailed structure of which is not shown in the figure, and are used for compensating the chromatic dispersion of the amplified chirped pulse, compressing the pulse width of the amplified pulse to be the narrowest, and improving the conversion efficiency in the harmonic generation process;
the laser harmonic generator adopts two identical lithium triborate (LBO) crystals 20 and 35 with the length of 2 mm, and the two amplified laser beams respectively generate second harmonics; lenses 19, 21, 34 and 36 are used for focusing of light of the fundamental frequency and collimation of green light, and filters 37 and 38 are used for separating the green light from the light of the fundamental frequency; the conversion efficiency of the two channels is kept consistent as much as possible;
the pulse beam combiner also adopts a non-polarization beam splitting cube 40 to combine two beams of green light, the piezoelectric deflection mirror 39 is used for adjusting the pointing direction of one beam of green light to be the same as that of the other beam, one of the beams in two emergent directions is synthetic light, the other path of loss light is reflected by the sampler 41 to be received by the four-quadrant detector 43, and the phase error and the pointing error of the green light of the two channels are detected; the remaining residual light is received by the light barrier 42;
the electric control loop locks the phase and the direction of the two-way light beam by adopting a LOCSET technology; through an electric control feedback loop consisting of an analog-to-digital converter, a single chip microcomputer and a digital-to-analog converter, sine phase modulation with certain frequency is applied to the piezoelectric ceramic driving mirror 8, phase errors and pointing errors obtained by a four-quadrant detector 43 are received and demodulated, the phase errors are fed back to the piezoelectric ceramic driving mirror 8 to realize phase locking, and the pointing errors are fed back to the piezoelectric deflection mirror 39 to realize pointing locking, so that the locking of the phase and the light beam pointing is realized simultaneously based on a single detector, and the piezoelectric ceramic driving mirror has good expansibility; the phase feedback is applied to the fundamental frequency light path, because the phase of the harmonic laser and the fundamental frequency light have a fixed relation in the harmonic generation process, and the phase of the harmonic laser can be indirectly controlled by controlling the phase of the fundamental frequency light.
The embodiment shows a device for obtaining high-power high-efficiency high-beam-quality femtosecond green light by coherent synthesis of two-channel green light, reduces the heat load on a single crystal by respectively performing a second harmonic generation process and then performing coherent synthesis on a multi-channel nonlinear crystal, and can realize high-stability high-power high-efficiency high-beam-quality green light output under active phase control and beam pointing control. The present embodiment represents only one embodiment of the present invention, and the present invention is not limited to the above-mentioned structure, and any structure based on first harmonic laser generation and then coherent combination to obtain high power harmonic output should be included in the protection scope of the present invention.

Claims (7)

1. A femtosecond laser harmonic generation system based on coherent beam combination is characterized by comprising a femtosecond pulse seed source, a pulse stretcher, a pulse beam splitter, an optical fiber amplifier, a pulse compressor, a laser harmonic generator, a pulse beam combiner and an electric control loop; wherein:
the femtosecond pulse seed source is used for generating a femtosecond pulse sequence with certain power, adopts a structure of an oscillator and power pre-amplification, and the output end of the femtosecond pulse seed source is connected with a pulse stretcher;
the pulse stretcher is used for stretching the pulse width of the pulse output by the seed source and amplifying the subsequent chirped pulse, and the output end of the pulse stretcher is connected with the pulse beam splitter;
the pulse beam splitter is used for spatially dividing the broadened pulses into multiple paths and is respectively connected with the corresponding optical fiber amplifiers;
the optical fiber amplifier is used for amplifying chirped pulses of the multi-channel expanded pulses to realize power boosting, and the outputs of the optical fiber amplifier are respectively connected with corresponding pulse compressors;
the pulse compressor is used for compressing the pulse width of the amplified pulse to be the narrowest, is matched with the pulse stretcher, improves the peak power and further improves the conversion efficiency in the harmonic generation process, and the output of the pulse compressor is respectively connected with the corresponding laser harmonic generator;
the laser harmonic generator is used for respectively realizing the phase matching process of the compressed multiple pulses in the multi-channel nonlinear crystal for harmonic generation, and the output of the laser harmonic generator is connected with the pulse beam combiner;
the pulse beam combiner is used for spatially combining a plurality of harmonic laser beams into one beam, and the combined beam is detected by the photoelectric detector and then is connected with the electric control loop;
the electric control loop is used for controlling phases of multiple beams of harmonic laser to be consistent, so that high-efficiency coherent synthesis is realized.
2. The coherent beam combination-based femtosecond laser harmonic generation system according to claim 1, wherein the femtosecond pulse seed oscillator mode-locking mode can be a nonlinear polarization rotation mode, a saturable absorber mode or a nonlinear amplification ring mirror mode.
3. The coherent beam combination-based femtosecond laser harmonic generation system according to claim 1, wherein the stretcher is a single-mode fiber or a bragg-body grating; the beam splitter is any one of a half-mirror, a polarizing beam splitter and a thin film polarizer.
4. The femtosecond laser harmonic generation system based on coherent beam combination according to claim 1, wherein the optical fiber used for the amplifier is a large mode area double-clad fiber, a photonic crystal fiber or a rod-shaped fiber.
5. The coherent beam combination-based femtosecond laser harmonic generation system according to claim 1, wherein the pulse compressor can be one or more of a grating pair, a Bragg body grating, a prism pair and a chirped mirror; the nonlinear crystal is one of lithium triborate, barium metaborate, potassium titanyl phosphate and periodically poled lithium niobate.
6. The coherent beam combination-based femtosecond laser harmonic generation system as claimed in claim 1, wherein the beam combination manner is selected to fill an aperture to obtain high synthesis efficiency, and the beam combiner is a half-mirror, a polarization beam splitter, or a thin-film polarizer.
7. The femtosecond laser harmonic generation system based on coherent beam combination as set forth in claim 1, wherein beam combination is performed by using a half-mirror, the electric control loop is phase-locked by using a single-detector frequency marking mode or a random parallel gradient descent mode, and if beam combination is performed by using polarization, the electric control loop is phase-locked by using a Hansch-Couillaud technology.
CN202210370906.7A 2022-02-21 2022-04-11 Femtosecond laser harmonic generation system based on coherent beam combination Pending CN114927921A (en)

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CN2022101589361 2022-02-21

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