Miniaturized space macro-energy ultraviolet single-frequency laser

Abstract

The invention provides a miniaturized spatial macro-energy ultraviolet single-frequency laser. The miniaturized spatial macro-energy ultraviolet single-frequency laser comprises a single-frequency pulse seed laser module, a three-stage amplifier and a nonlinear transformation module, the single-frequency pulse seed laser is a passively Q-switched single non-planar annular cavity and can output single-frequency 1064nm pulse laser of ten microfocus magnitude. The three-stage amplifier adopts a compact side pumping batten crystal structure, so that 1064nm single-frequency laser output with energy of 350mJ can be realized; by improving the output energy of the first amplifier, high-gain amplification of small-signal incident laser pulses is realized, and the pressure of subsequent amplification is reduced; the nonlinear transformation module can realize long-life and high-reliability ultraviolet single-frequency pulse output of hundred millijoule and hundred hertz by controlling the power density; the method can be used for satellite-borne hyperspectral laser radars, satellite-borne wind measurement laser radars and the like to obtain global meteorological information. The invention mainly solves the problems of miniaturization, high frequency stability and high reliability of the large-energy space ultraviolet single-frequency laser.

Description

Technical Field

[0001] The invention relates to the technical field of lasers, and in particular to a miniaturized spatial high-energy ultraviolet single-frequency laser. Background Art

[0002] Spaceborne hyperspectral lidar can quantitatively obtain multi-parameter information of cloud-aerosol; spaceborne wind lidar is the only means to obtain high-precision global wind profiles; spaceborne greenhouse gas differential absorption lidar can effectively monitor the concentration changes of methane and carbon dioxide. All of the above lidars require lasers with high energy and single-frequency pulse characteristics.

[0003] There are generally two ways to achieve high-energy single-frequency pulse lasers: one is seed injection locking plus amplification, injecting continuous single-frequency seed lasers into the driven laser to achieve single-frequency pulse laser output, and then passing through a multi-stage amplifier to achieve high-energy single-frequency pulse laser output; the other is to amplify the continuous single-frequency seed laser after chopping and shaping, first passing through a fiber amplifier to amplify the energy to the microjoule level, and then through an end-pumped rod crystal to amplify the energy to the millijoule level, and then passing through a multi-stage amplifier to achieve high-energy single-frequency pulse laser output. Among them, the injection locking scheme has a complex control circuit, and the uncertainty of the Q switch opening time introduces a certain frequency jitter to the single-frequency pulse laser; the chopping amplification scheme requires the use of two additional AOMs, which increases the system power consumption. At the same time, fiber amplification and end-face rod crystal pre-amplification are also required, and the system complexity is high; the two schemes have high system complexity and are not advantageous in terms of miniaturization and low power consumption requirements for space applications.

[0004] Therefore, a small, stable, high-energy, single-frequency pulsed laser is needed. Summary of the invention

[0005] The invention aims to solve the problems of efficient amplification, stability and miniaturization of a compact structure of a single-frequency pulse of the order of ten microjoules, and provides a miniaturized space large-energy ultraviolet single-frequency laser, comprising a single-frequency pulse seed laser module, a three-stage amplifier and a nonlinear conversion module; the single-frequency pulse seed laser is a passively Q-switched single-block non-planar ring cavity, which can output a single-frequency 1064nm pulse laser of the order of ten microjoules; the three-stage amplifiers all adopt a compact side-pumped slab crystal structure, which can realize the output of a 1064nm single-frequency laser with an energy of 350mJ; the nonlinear conversion module can realize long-life, high-reliability ultraviolet single-frequency pulse output of hundreds of millijoules and hundreds of hertz by controlling the power density; it can be used for satellite-borne hyperspectral laser radars, satellite-borne wind measurement laser radars and the like to obtain global meteorological information; the invention mainly solves the problems of miniaturization, high-frequency stability and high reliability of a large-energy space ultraviolet single-frequency laser.

[0006] The present invention provides a miniaturized spatial high-energy ultraviolet single-frequency laser, comprising a single-frequency pulse seed laser module, a three-stage amplifier and a nonlinear conversion module optically connected in sequence;

[0007] The single-frequency pulse seed laser module outputs a single-frequency pulse laser of the order of ten microjoules and injects it into the three-stage amplifier. The three-stage amplifier amplifies the single-frequency pulse laser and then outputs it to the nonlinear conversion module. The nonlinear conversion module generates an ultraviolet single-frequency pulse laser.

[0008] The three-stage amplifier comprises a first amplifier component, a second amplifier component and a third amplifier component which are optically connected in sequence. The single-frequency pulse laser of ten microjoules outputted by the single-frequency pulse seed laser module is subjected to two-stage double-pass amplification in the first amplifier component and the second amplifier component through polarization state control. The first amplifier component performs double-pass amplification on the single-frequency pulse laser of ten microjoules through slab crystal side pumping and Paul prism to obtain a single-stage amplified single-frequency laser, and the energy of the single-stage amplified single-frequency laser is more than 3mJ; the second amplifier component performs double-pass amplification on the single-frequency laser through slab crystal side pumping and Paul prism to obtain a second-stage amplified single-frequency laser; the third amplifier component performs single-pass amplification on the second-stage amplified single-frequency laser through slab crystal double-side pumping to obtain a tertiary amplified single-frequency laser and outputs it to the nonlinear conversion module;

[0009] The nonlinear conversion module outputs ultraviolet single-frequency laser greater than 100mJ.

[0010] The miniaturized spatial high-energy ultraviolet single-frequency laser described in the present invention, as a preferred embodiment, the single-frequency pulse seed laser module includes a single-frequency pulse seed laser, a first isolator, a first 1 / 2 wave plate, a first beam expansion lens group and a first polarizer optically connected in sequence;

[0011] The single-frequency pulse seed laser outputs a single-frequency pulse laser of the order of ten microjoules, the first isolator allows the single-frequency pulse laser of the order of ten microjoules to pass unidirectionally to prevent feedback light from damaging the single-frequency pulse seed laser, the first 1 / 2 wave plate adjusts the polarization state of the single-frequency pulse laser of the order of ten microjoules to a p-state, the first beam expansion lens group performs beam transformation on the p-polarized single-frequency pulse seed light of the order of ten microjoules, and the first polarizer injects the p-polarized single-frequency pulse of the order of ten microjoules into the first amplifier component;

[0012] The energy of the double-amplified single-frequency laser is greater than 35mJ, and the energy of the tertiary-amplified single-frequency laser is greater than 350mJ.

[0013] The miniaturized space large energy ultraviolet single-frequency laser described in the present invention is preferably a single-frequency pulse seed laser with an operating frequency of 100 Hz, an output of 1064 nm single-frequency pulse laser of ten microjoules, and a beam quality of M 2 Less than 1.3 times the diffraction limit;

[0014] The single-frequency pulse seed laser includes a seed laser pump source, a pump coupling lens group and a single non-planar ring cavity. The single non-planar ring cavity uses diffusion bonding to connect the Nd:YAG laser gain crystal with the Cr 4+ :YAG passive Q-switched saturable absorption crystal bonding, combined with active pump control to output single-frequency pulse laser with energy of tens of microjoules and adjustable repetition frequency of 1Hz to 1kHz.

[0015] The miniaturized spatial high-energy ultraviolet single-frequency laser described in the present invention, as a preferred embodiment, the first amplifier assembly includes a first amplifier, a first compensation wave plate, a first concave lens and a first Paul prism which are located on the transmission light path of the first polarizer and optically connected in sequence;

[0016] The first amplifier includes four side surfaces, the long side surface is a pumping surface, and the other three side surfaces are cooling surfaces, and the cooling surface is connected to the copper heat sink through indium foil or indium welding; the first concave lens compensates for the thermal lens effect of the slat crystal, the first compensation wave plate and the first Paul prism flip the laser polarization state and the spot direction by 90° to perform double-pass amplification and thermal distortion correction of the spot, and the first amplifier outputs the double-pass amplified, s-polarized state, once-amplified single-frequency laser to the first polarizer.

[0017] The miniaturized spatial high-energy ultraviolet single-frequency laser described in the present invention, as a preferred embodiment, the second amplifier assembly includes a second isolator, a second 1 / 2 wave plate, a second beam expanding lens group, a second polarizer, a second amplifier, a second compensation wave plate, a second concave lens and a second Paul prism, which are optically connected to the refractive optical path of the first polarizer in sequence;

[0018] The once-amplified single-frequency laser is reflected by the first polarizer to the second isolator, the second isolator prevents the return light of the rear optical path from causing disturbance to the first amplifier component, the second 1 / 2 wave plate adjusts the polarization state of the once-amplified single-frequency laser to the p-state, the second beam expanding lens group performs beam transformation on the p-polarized once-amplified single-frequency laser, the second polarizer makes the p-polarized once-amplified single-frequency laser incident on the second amplifier, the second concave lens compensates for the thermal lens effect of the slat crystal, the second compensation wave plate and the second Paul prism flip the laser polarization state and the spot direction by 90 degrees for double-pass amplification and thermal distortion correction of the spot, and the second amplifier outputs the second-amplified single-frequency laser to the second polarizer;

[0019] The second amplifier comprises four side surfaces, the long side surface is a pumping surface, and the other three side surfaces are cooling surfaces, and the cooling surface is connected to the copper heat sink through indium foil or indium solder.

[0020] The miniaturized spatial high-energy ultraviolet single-frequency laser described in the present invention, as a preferred embodiment, the third amplifier assembly includes a third 1 / 2 wave plate, a third beam expander lens group, a third amplifier, a cylindrical lens group and a fourth 1 / 2 wave plate optically connected to the second polarizer reflection light path in sequence;

[0021] The third 1 / 2 wave plate adjusts the polarization state of the secondary amplified single-frequency laser to the p-state, the third beam expanding lens group performs beam transformation on the p-polarized secondary amplified single-frequency laser, the third amplifier makes the p-polarized secondary amplified single-frequency laser advance in a Z-shape, the cylindrical lens group performs thermal distortion correction on the light spot of the third amplifier and outputs the tertiary amplified single-frequency laser, and the fourth 1 / 2 wave plate adjusts the polarization state of the tertiary amplified single-frequency laser to the s-state;

[0022] The third amplifier is double-sided pumped and double-sided cooled, and the cooling surface is connected to the copper heat sink through indium foil or indium solder.

[0023] The miniaturized spatial high-energy ultraviolet single-frequency laser described in the present invention is preferably configured such that the first amplifier and the second amplifier are both Nd:YAG slab crystals with a doping concentration of 1% and a length of 56 mm;

[0024] The pump sources of the first and second amplifiers are three groups of 808nm LD arrays located at the laser footprint on one side. Each group of LD arrays contains six bars, and the peak power of a single bar is 100W.

[0025] Both end faces of the Nd:YAG slab crystals of the first and second amplifiers are coated with 45° antireflection coatings for 1064nm horizontal polarization and vertical polarization;

[0026] The third amplifier is a Nd:YAG slab crystal with a doping concentration of 0.8% and a length of 160 mm;

[0027] The pump source of the third amplifier is 9 groups of 808nm LD arrays located at the laser footprints on both sides. Each group of LD arrays contains 10 bars, and the peak power of a single bar is 100W.

[0028] The distance between the LD arrays of the first amplifier, the second amplifier and the third amplifier and the Nd:YAG slab crystal is 1 mm.

[0029] The miniaturized spatial large-energy ultraviolet single-frequency laser described in the present invention is preferably a nonlinear conversion module comprising a first LBO crystal, a second LBO crystal, a dichroic mirror and an optical trash can optically connected to the output end of the three-stage amplifier in sequence, and the refraction output end of the dichroic mirror outputs an ultraviolet single-frequency laser greater than 100mJ;

[0030] The first LBO crystal performs frequency doubling, the second LBO crystal performs frequency summing, the color dichroic mirror transmits single-frequency laser, and the optical trash can receives lasers of other wavelengths.

[0031] The miniaturized spatial high-energy ultraviolet single-frequency laser described in the present invention is preferably configured such that the first LBO crystal performs frequency doubling of 1064nm to obtain 532nm laser output, the second LBO crystal performs frequency summing of 1064nm laser and 532nm laser to obtain 355nm laser output, the dichroic mirror has high transmittance to 1064nm laser and 532nm laser and high reflectivity to 355nm laser to emit 355nm laser, and the optical trash can receives 1064nm laser and 532nm laser.

[0032] The miniaturized space-based high-energy ultraviolet single-frequency laser described in the present invention is preferably configured such that the temperature control accuracy of the first LBO crystal and the second LBO crystal are both 0.01 degrees Celsius;

[0033] The first LBO crystal uses type I phase matching to control the maximum peak power of the incident laser to 100MW / cm 2 , control the maximum value of the double frequency efficiency to 50%;

[0034] The second LBO crystal uses type II phase matching to control the maximum peak power of the incident laser to 100MW / cm 2 , controlling the maximum value of triple frequency efficiency to 30%.

[0035] In the present invention, the divergence angles of the first concave lens and the second concave lens are adjusted so that the divergence angle of the outgoing light spot is substantially consistent with the divergence angle of the incident light spot, thereby ensuring that the return laser and the pump light also have good mode matching.

[0036] The invention provides a miniaturized space large-energy ultraviolet single-frequency laser, comprising a single-frequency pulse seed laser, a three-stage amplifier, and a nonlinear conversion module; the single-frequency pulse seed laser is a passively Q-switched single-block non-planar ring cavity, which can output a single-frequency 1064nm pulse laser of the order of ten microjoules; the three-stage amplifiers all adopt a compact side-pumped slab crystal structure, which can achieve an energy of 350mJ 1064nm single-frequency laser output; the nonlinear conversion module can achieve long-life, high-reliability ultraviolet single-frequency pulse output of hundreds of millijoules and hundreds of hertz by controlling the power density; the laser can be used for satellite-borne hyperspectral laser radars, satellite-borne wind measurement laser radars, etc., to obtain global meteorological information; the invention mainly solves the problems of miniaturization, high frequency stability, and high reliability of large-energy space ultraviolet single-frequency lasers.

[0037] The present invention has the following advantages:

[0038] (1) The present invention innovatively combines a single-frequency pulse seed laser of the order of ten microjoules with a first-stage dual-pass amplifier of a side-pumped slab crystal, thereby avoiding the complex structure of continuous seed source AOM chopping followed by fiber amplification and end-pumped rod crystal heterogeneous hybrid amplification, greatly simplifying the complex control circuit and complex optical path of the traditional implementation method and reducing the size of the laser.

[0039] (2) The present invention improves the output energy of the first amplifier, realizes high-gain amplification of small-signal incident laser pulses, and reduces the pressure of subsequent amplification; the first and second amplifiers use compensation wave plates and Paul prisms combined with concave lenses for double-pass amplification to achieve thermal lens effect compensation of the slab crystal and correction of thermal distortion of the light spot; a suitable beam expansion factor is selected before the multi-stage amplifier for beam transformation, and a suitable distance is selected between the amplifier LD and the slab crystal to optimize the mode matching of the laser and improve the amplification efficiency.

[0040] (3) The present invention can output single-frequency ultraviolet lasers of hundreds of hertz and hundreds of millijoules through a conduction cooling method, which can simultaneously meet the requirements of satellite-borne laser radars for high energy, single frequency, miniaturization, and high reliability of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a system block diagram of a miniaturized space high-energy ultraviolet single-frequency laser;

[0042] Figure 2 This is a schematic diagram of a miniaturized space high-energy ultraviolet single-frequency laser;

[0043] Figure 3 It is a curve diagram of the change of the output energy of the first-stage and second-stage amplification of a miniaturized space large-energy ultraviolet single-frequency laser with the pump energy;

[0044] Figure 4 This is a curve diagram showing the change of output energy of a three-stage amplification with pump energy based on the principle of a miniaturized space high-energy ultraviolet single-frequency laser.

[0045] Reference numerals:

[0046] 1. Single-frequency pulse seed laser module; 11. Single-frequency pulse seed laser; 12. First isolator; 13. First 1 / 2 wave plate; 14. First beam expander lens group; 15. First polarizer; 2. Three-stage amplifier; 21. First amplifier assembly; 211. First amplifier; 212. First compensation wave plate; 213. First concave lens; 214. First Paul prism; 22. Second amplifier assembly; 221. Second isolator; 222. Second 1 / 2 wave plate; 223. Second beam expander Lens group; 224, second polarizer; 225, second amplifier; 226, second compensation wave plate; 227, second concave lens; 228, second Paul prism; 23, third amplifier assembly; 231, third 1 / 2 wave plate; 232, third beam expander lens group; 233, third amplifier; 234, cylindrical lens group; 235, fourth 1 / 2 wave plate; 3, nonlinear transformation module; 31, first LBO crystal; 32, second LBO crystal; 33, color dichroic mirror; 34, optical trash can. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0048] Example 1

[0049] like Figure 1 , 2 As shown, a miniaturized spatial high-energy ultraviolet single-frequency laser comprises a single-frequency pulse seed laser module 1, a three-stage amplifier 2, and a nonlinear conversion module 3;

[0050] The single-frequency pulse seed laser module 1 outputs a single-frequency pulse laser of the order of ten microjoules, which is then injected into the three-stage amplifier 2; the multi-stage amplifier 2 amplifies the single-frequency pulse laser and then sends it to the nonlinear transformation module 3; the nonlinear transformation module 3 generates an ultraviolet single-frequency pulse laser.

[0051] The single-frequency pulse seed laser 1 is a passively Q-switched single-block non-planar ring cavity laser. 4+ :YAG passively Q-switched saturable absorption crystals are bonded together to form a single non-planar annular cavity, which, combined with active pump control, can output a 1064nm single-frequency pulse laser with an energy of tens of microjoules and an adjustable repetition frequency of 1Hz to 1kHz.

[0052] The single-frequency pulse seed laser module 11 includes a seed laser pump source, a pump coupling lens group, and a single non-planar ring cavity, wherein the single non-planar ring cavity uses a diffusion bonding technology to connect a Nd:YAG laser gain crystal with a Cr 4+:YAG passively Q-switched saturable absorption crystals are bonded together and processed. Combined with active pump control, it can output single-frequency pulse lasers with energy levels of tens of microjoules and adjustable repetition frequency of 1Hz to 1kHz.

[0053] The single-frequency pulse seed laser 11 operates at 100 Hz.

[0054] The three-stage amplifier includes a first amplifier 21, a second amplifier 22, and a third amplifier 23. Two-stage double-pass amplification is performed in the first amplifier 21 and the second amplifier 22 through polarization state control; and the third amplifier 23 performs single-pass amplification.

[0055] Light beam transformation is performed before the first amplifier 21, the second amplifier 22 and the third amplifier 23 respectively to ensure that the three-stage amplifier has high amplification efficiency.

[0056] The three-stage amplifiers 21, 22, and 23 use Nd:YAG slab crystals. The laser advances in a zigzag pattern in the slab crystals. A laser diode (LD) is placed at the laser footprint for side pumping.

[0057] The four sides of the Nd:YAG slab crystal of the first amplifier 21 and the second amplifier 22 have the long sides as pumping surfaces and the other three sides as cooling surfaces, which are connected to the copper heat sink through indium foil or indium solder.

[0058] Both end faces of the Nd:YAG slab crystals of the first amplifier 21 and the second amplifier 22 are coated with 45° anti-reflection films of 1064nm horizontal polarization and vertical polarization.

[0059] The four sides of the Nd:YAG slab crystal of the third amplifier 23 are double-sided pumped and double-sided cooled, and the cooling surface is connected to the copper heat sink through indium foil or indium solder.

[0060] The three-stage amplifier 2 is thermally controlled by conduction cooling.

[0061] The first amplifier 21 and the second amplifier 22 compensate for the thermal lens effect through a concave lens.

[0062] The first amplifier 21 and the second amplifier 22 use Porro prisms 214 and 228 to flip the light spot direction by 90 degrees to correct the light spot thermal distortion, and the third amplifier 23 uses a cylindrical mirror 234 to correct the light spot thermal distortion.

[0063] The nonlinear conversion module 3 uses a high-precision temperature-controlled LBO crystal, and controls the triple frequency efficiency to 30% by reducing the laser power density.

[0064] The nonlinear conversion module 3 includes a first LBO crystal 31, a second LBO crystal 32, a dichroic mirror 33, and an optical trash can 34. The 1064nm single-frequency pulse laser emitted by the three-stage amplifier 2 enters the first LBO crystal 31 for frequency doubling and then emits 1064nm and 532nm single-frequency pulse lasers. The doubled 1064nm and 532nm single-frequency pulse lasers enter the second LBO crystal 32 for frequency summing, and then emit 1064nm, 532nm, and 355nm single-frequency pulse lasers. After being split by the dichroic mirror 33, 355nm single-frequency pulse lasers are emitted. The remaining 1064nm and 532nm single-frequency pulse lasers enter the optical trash can 34.

[0065] The temperature control accuracy of the first LBO crystal 31 and the second LBO crystal 32 of the nonlinear conversion module 3 is 0.01 degrees Celsius.

[0066] The single-frequency pulse seed laser 1 outputs a 1064nm single-frequency pulse laser of ten microjoules, with a beam quality of M 2 Less than 1.3 times the diffraction limit.

[0067] Specific:

[0068] Figure 1 This is a block diagram of the miniaturized space large energy ultraviolet single-frequency pulse laser system of the present invention. Among them, the single-frequency pulse seed laser 1 outputs a 1064nm single-frequency pulse laser of the order of ten microjoules; the first amplifier 21 amplifies the single-frequency pulse energy to 3mJ through double-pass amplification; the second amplifier 22 amplifies the single-frequency pulse energy to 35mJ through double-pass amplification; the third amplifier 23 amplifies the single-frequency pulse energy to 350mJ through single-pass amplification; and the nonlinear conversion module realizes a 355nm wavelength laser output greater than 100mJ.

[0069] Figure 2This is the principle diagram of the miniaturized space large energy ultraviolet single-frequency pulse laser of this embodiment. The single-frequency pulse seed laser 11 outputs a single-frequency pulse laser of the order of ten microjoules. The first isolator 12 ensures that 1064nm passes unidirectionally to prevent feedback light from causing damage to the seed laser; the first 1 / 2 wave plate 13 adjusts the polarization state of the 1064nm single-frequency pulse laser to make its polarization state p light, the first beam expansion lens group 14 performs beam transformation on the single-frequency pulse seed light to make the first amplifier have high amplification efficiency, the seed pulse laser is incident on the first amplifier 211 through the first polarizer 15, the first concave lens 213 optimizes the mode matching of the laser to realize the thermal lens effect compensation of the slab crystal, and the first compensation wave plate 212 The first Porro prism 214 flips the laser polarization state and the light spot direction by 90° to realize double-pass amplification and correction of thermal distortion of the light spot. The laser after double-pass amplification by the first amplifier 211 is reflected by the first polarizer 15 and incident on the second isolator 221. The second isolator 221 prevents the return light of the rear optical path from causing disturbance to the first amplifier 211, thereby realizing pulse laser amplification with high energy stability. The second 1 / 2 wave plate 222 adjusts the polarization state of the laser to make it p-light. The second beam expander lens group 223 performs beam transformation on the laser so that the second amplifier has high amplification efficiency. The laser output by the first amplifier 211 is The second polarizer 224 is incident on the second amplifier 225, the second concave lens 227 optimizes the mode matching of the laser to realize the compensation of the thermal lens effect of the slat crystal, the second compensation wave plate 226 and the second Paul prism 228 flip the laser polarization state and the spot direction by 90 degrees to realize double-pass amplification and thermal distortion correction of the spot, and the laser after double-pass amplification by the second amplifier assembly 22 is reflected by the second polarizer 224 and incident on the third 1 / 2 wave plate 231; the third 1 / 2 wave plate 231 adjusts the polarization state of the laser to make its polarization state p light, and the third beam expander lens group 232 performs beam transformation on the laser to make the third amplifier 233 It has high amplification efficiency. The cylindrical lens group 234 is used to realize the thermal distortion correction of the light spot of the third amplifier 233. The fourth 1 / 2 wave plate 235 adjusts the polarization state of the laser to make its polarization state s-light. The first LBO crystal 31 realizes the frequency doubling of 1064nm to obtain 532nm laser output. The second LBO crystal 32 realizes the sum frequency of 1064nm and 532nm to obtain 355nm laser output. The color dichroic mirror 33 has high transmittance to 1064nm and 532nm and high reflection to 355nm, so as to realize the emission of 355nm laser. The optical trash can 34 receives 1064nm and 532nm laser.

[0070] Preferably, the Nd:YAG crystal doping concentration of the single-frequency pulse seed laser 11 is 1%, and the repetition frequency is 100 Hz.

[0071] Preferably, the Nd:YAG slab crystals of the first amplifier 211 and the second amplifier 225 have a doping concentration of 1% and a length of 56 mm.

[0072] Preferably, the pump sources of the first amplifier 211 and the second amplifier 225 use three groups of 808nm LD arrays, each group of arrays includes six bars, and the peak power of a single bar is 100W.

[0073] Preferably, the doping concentration of the Nd:YAG slab crystal of the third amplifier 225 is 0.8%, and the length is 160 mm.

[0074] Preferably, the pump source of the third amplifier 225 uses 9 groups of 808nm LD arrays, each group of arrays includes 10 bars, and the peak power of a single bar is 100W.

[0075] Preferably, the distance between the LD and the Nd:YAG slab crystal in the multi-stage amplifier 2 is 1 mm.

[0076] Preferably, the first LBO crystal 31 adopts type I phase matching to control the incident laser peak power to 100 MW / cm 2 , controlling the double frequency efficiency to ~50%;

[0077] Preferably, the second LBO crystal 32 adopts type II phase matching to control the incident laser peak power to 100 MW / cm 2 , controlling the triple frequency efficiency to ~30% can improve the life of high-energy ultraviolet single-frequency lasers.

[0078] The present invention adopts a compact and efficient slab crystal amplification module to amplify a single-frequency pulse monolithic non-planar ring cavity seed laser to obtain a large-energy single-frequency 1064nm, avoiding the frequency jitter generated by the injection locking scheme and improving the frequency stability. The ten-microjoule-level single-frequency pulse seed laser 11 is combined with a side-pumped slab crystal first-stage double-pass amplifier, which not only avoids the complex structure of fiber amplification and end-pumped rod-shaped crystal heterogeneous hybrid amplification after continuous seed source AOM chopping, but also greatly simplifies the complex control circuit and complex optical path of the traditional implementation method, and reduces the volume of the laser; it also increases the output energy of the first amplifier 211, realizes high-gain amplification of the incident laser pulse of the small signal, and reduces the pressure of subsequent amplification. The first amplifier 211 and the second amplifier 225 use a compensation wave plate and a Paul prism combined with a concave lens for double-pass amplification, realizing the compensation of the thermal lens effect of the slab crystal and the correction of the thermal distortion of the light spot. The appropriate beam expansion multiple is selected before the multi-stage amplifier for beam transformation, and the amplifier LD and the slab crystal are selected at a suitable distance to optimize the mode matching of the laser and improve the amplification efficiency. By controlling the laser peak power density, the triple frequency efficiency is controlled to 30%, thereby improving the life and reliability of the high-energy ultraviolet single-frequency laser. In summary, the present invention can obtain high-frequency stability, high reliability, long-life high-energy single-frequency laser output, and has the advantage of miniaturization, and is the preferred light source for space laser radar.

[0079] Implementation effect: The satellite-borne high-energy 355nm single-frequency pulse laser uses this invention. The single-frequency pulse seed laser with a repetition frequency of 100Hz outputs 20μJ of 1064nm single-frequency pulse laser; the first amplifier 211 amplifies the single-frequency pulse energy to 3.1mJ through double-pass amplification; the second amplifier 225 amplifies the single-frequency pulse energy to 35.6mJ through double-pass amplification; the third amplifier 233 amplifies the single-frequency pulse energy to 350.3mJ through single-pass amplification; the nonlinear conversion module 3 realizes 112mJ of 355nm wavelength laser output. The curve of the output energy of the three-stage amplification with the pump energy is shown in Figure 3 and Figure 4 .

[0080] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A miniaturized, high-energy, ultraviolet single-frequency laser, characterized in that: It comprises a single-frequency pulse seed laser module (1), a three-stage amplifier (2) and a nonlinear conversion module (3) which are optically connected in sequence; The single-frequency pulse seed laser module (1) outputs a single-frequency pulse laser of the order of ten microjoules and injects it into the three-stage amplifier (2); the three-stage amplifier (2) amplifies the single-frequency pulse laser and then outputs it to the nonlinear conversion module (3); the nonlinear conversion module (3) generates ultraviolet single-frequency pulse laser; The three-stage amplifier (2) comprises a first amplifier component (21), a second amplifier component (22) and a third amplifier component (23) which are optically connected in sequence. The single-frequency pulse laser light of ten microjoules output by the single-frequency pulse seed laser module (1) is subjected to two-stage double-pass amplification in the first amplifier component (21) and the second amplifier component (22) through polarization state control. The first amplifier component (21) performs double-pass amplification on the single-frequency pulse laser light of ten microjoules through slab crystal side pumping and Por prism to obtain a single-stage amplified single-frequency laser light, wherein the energy of the single-stage amplified single-frequency laser light is greater than 3 mJ. The second amplifier component (22) performs double-pass amplification on the single-frequency laser light of the first stage amplified single-frequency laser light through slab crystal side pumping and Por prism to obtain a second-stage amplified single-frequency laser light. The third amplifier component (23) performs single-pass amplification on the second-stage amplified single-frequency laser light through slab crystal double-side pumping to obtain a third-stage amplified single-frequency laser light and outputs the laser light to the nonlinear conversion module (3). The nonlinear conversion module (3) outputs ultraviolet single-frequency laser light greater than 100 mJ.

2. A miniaturized spatial high energy ultraviolet single frequency laser according to claim 1, characterized in that: The single-frequency pulse seed laser module (1) comprises a single-frequency pulse seed laser (11), a first isolator (12), a first 1 / 2 wave plate (13), a first beam expansion lens group (14) and a first polarizer (15) which are optically connected in sequence; The single-frequency pulse seed laser (11) outputs the ten-microjoule-level single-frequency pulse laser, the first isolator (12) allows the ten-microjoule-level single-frequency pulse laser to pass unidirectionally to prevent feedback light from damaging the single-frequency pulse seed laser (11), the first 1 / 2 wave plate (13) adjusts the polarization state of the ten-microjoule-level single-frequency pulse laser to a p-state, the first beam expansion lens group (14) performs beam conversion and amplifier on the p-polarized ten-microjoule-level single-frequency pulse seed light, and the first polarizer (15) causes the p-polarized ten-microjoule-level single-frequency pulse to be incident on the first component (21); The energy of the twice-amplified single-frequency laser is greater than 35 mJ, and the energy of the tertiary-amplified single-frequency laser is greater than 350 mJ.

3. A miniaturized spatial high energy ultraviolet single frequency laser according to claim 2, characterized in that: The single-frequency pulse seed laser (11) has an operating frequency of 100 Hz, outputs a 1064 nm single-frequency pulse laser of ten microjoules, and has a beam quality of M 2 Less than 1.3 times the diffraction limit; The single-frequency pulse seed laser (11) comprises a seed laser pump source, a pump coupling lens group and a single non-planar ring cavity. The single non-planar ring cavity uses diffusion bonding to connect a Nd:YAG laser gain crystal with a Cr 4+ :YAG passive Q-switched saturable absorption crystal bonding, combined with active pump control to output single-frequency pulse laser with energy of tens of microjoules and adjustable repetition frequency of 1Hz to 1kHz.

4. The miniaturized spatial high energy ultraviolet single frequency laser according to claim 2, characterized in that: The first amplifier component (21) comprises a first amplifier (211), a first compensation wave plate (212), a first concave lens (213) and a first Paul prism (214) which are located on the transmission light path of the first polarizer (15) and optically connected in sequence; The first amplifier (211) comprises four side surfaces, the long side surface is a pumping surface, and the other three side surfaces are cooling surfaces, and the cooling surface is connected to the copper heat sink through indium foil or indium solder; the first concave lens (213) compensates for the thermal lens effect of the slab crystal, the first compensation wave plate (212) and the first Paul prism (214) flip the laser polarization state and the light spot direction by 90 degrees to perform double-pass amplification and light spot thermal distortion correction, and the first amplifier (211) outputs the double-pass amplified, s-polarized state, single-frequency laser to the first polarizer (15).

5. A miniaturized spatial high energy ultraviolet single frequency laser according to claim 4, characterized in that: The second amplifier component (22) comprises a second isolator (221), a second 1 / 2 wave plate (222), a second beam expanding lens group (223), a second polarizer (224), a second amplifier (225), a second compensation wave plate (226), a second concave lens (227) and a second Paul prism (228) which are optically connected in sequence to the refractive light path of the first polarizer (15); The once-amplified single-frequency laser is reflected by the first polarizer (15) to the second isolator (221), the second isolator (221) prevents the return light of the rear optical path from causing disturbance to the first amplifier component (21), the second 1 / 2 wave plate (222) adjusts the polarization state of the once-amplified single-frequency laser to the p-state, the second beam expanding lens group (223) performs beam transformation on the p-polarized once-amplified single-frequency laser, the second polarizer (224) allows the p-polarized once-amplified single-frequency laser to be incident on the second amplifier (225), the second concave lens (227) compensates for the thermal lens effect of the slab crystal, the second compensation wave plate (226) and the second Paul prism (228) flip the laser polarization state and the light spot direction by 90 degrees to perform double-pass amplification and light spot thermal distortion correction, and the second amplifier (225) outputs the second-amplified single-frequency laser to the second polarizer (224); The second amplifier (225) comprises four side surfaces, the long side surface is a pumping surface, and the other three side surfaces are cooling surfaces, and the cooling surface is connected to the copper heat sink through indium foil or indium solder.

6. A miniaturized spatial high energy ultraviolet single frequency laser according to claim 5, characterized in that: The third amplifier assembly (23) comprises a third 1 / 2 wave plate (231), a third beam expander lens group (232), a third amplifier (233), a cylindrical lens group (234) and a fourth 1 / 2 wave plate (235) which are optically connected in sequence to the reflection light path of the second polarizing plate (224); The third 1 / 2 wave plate (231) adjusts the polarization state of the secondarily amplified single-frequency laser to the p-state, the third beam expanding lens group (232) performs beam transformation on the p-polarized secondarily amplified single-frequency laser, the third amplifier (233) causes the p-polarized secondarily amplified single-frequency laser to advance in a zigzag pattern, the cylindrical lens group (234) performs thermal distortion correction on the light spot of the third amplifier (233) and outputs the tertiary amplified single-frequency laser, and the fourth 1 / 2 wave plate (235) adjusts the polarization state of the tertiary amplified single-frequency laser to the s-state; The third amplifier (233) is double-sided pumped and double-sided cooled, and the cooling surface is connected to the copper heat sink via indium foil or indium soldering.

7. A miniaturized spatial high energy ultraviolet single frequency laser according to claim 6, characterized in that: The first amplifier (211) and the second amplifier (225) are both Nd:YAG slab crystals with a doping concentration of 1% and a length of 56 mm; The pump sources of the first amplifier (211) and the second amplifier (225) are three groups of 808nm LD arrays located at the laser footprint on one side, each group of LD arrays includes six bars, and the peak power of a single bar is 100W; Both end faces of the Nd:YAG slab crystals of the first amplifier (211) and the second amplifier (225) are coated with 45° anti-reflection films for 1064nm horizontal polarization and vertical polarization; The third amplifier (233) is a Nd:YAG slab crystal with a doping concentration of 0.8% and a length of 160 mm; The pump source of the third amplifier (233) is 9 groups of 808nm LD arrays located at the laser footprints on both sides, each group of LD arrays contains 10 bars, and the peak power of a single bar is 100W; The distance between the LD arrays of the first amplifier (211), the second amplifier (225) and the third amplifier (233) and the Nd:YAG slab crystal is 1 mm.

8. The miniaturized spatial high energy ultraviolet single frequency laser according to claim 3, characterized in that: The nonlinear conversion module (3) comprises a first LBO crystal (31), a second LBO crystal (32), a dichroic mirror (33) and an optical trash can (34) which are optically connected to the output end of the three-stage amplifier (2) in sequence, and the refraction output end of the dichroic mirror (33) outputs ultraviolet single-frequency laser light greater than 100 mJ; The first LBO crystal (31) performs frequency doubling, the second LBO crystal (32) performs frequency summing, the dichroic mirror (33) emits single-frequency laser light, and the optical trash can (34) receives laser light of other wavelengths.

9. The miniaturized spatial high energy ultraviolet single frequency laser according to claim 8, characterized in that: The first LBO crystal (31) performs frequency doubling of 1064nm to obtain 532nm laser output, the second LBO crystal (32) performs frequency doubling of 1064nm laser and 532nm laser to obtain 355nm laser output, the dichroic mirror (33) has high transmittance to 1064nm laser and 532nm laser and high reflectance to 355nm laser to emit 355nm laser, and the optical trash can (34) receives 1064nm laser and 532nm laser.

10. The miniaturized spatial high energy ultraviolet single frequency laser according to claim 8, characterized in that: The temperature control accuracy of the first LBO crystal (31) and the second LBO crystal (32) is 0.01 degrees Celsius; The first LBO crystal (31) uses type I phase matching to control the maximum value of the incident laser peak power to be 100 MW / cm 2 , control the maximum value of the double frequency efficiency to 50%; The second LBO crystal (32) uses type II phase matching to control the maximum value of the incident laser peak power to be 100 MW / cm 2 , controlling the maximum value of triple frequency efficiency to 30%.

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