A high-power nanosecond ultraviolet laser

Abstract

The present invention proposes a high-power nanosecond ultraviolet laser, which relates to the technical field of solid lasers, including a first pump source, a first pump mirror, a first gain crystal, a second gain crystal, a second pump mirror and a second pump source arranged in sequence along the light-emitting direction of the first pump source; the first pump light emitted by the first pump source is transmitted to the first gain crystal, the second gain crystal and the second pump mirror in sequence through the first pump mirror, the first pump light is reflected by the second pump mirror, so that the reflected light of the second pump mirror is transmitted to the Q-switched device and the first reflector in sequence, the second pump light emitted by the second pump source is transmitted to the second gain crystal, the first gain crystal and the first pump mirror in sequence through the second pump mirror, the second pump light is reflected by the first pump mirror, so that the reflected light of the first pump mirror is reflected to the second reflector; the reflected light of the second reflector is transmitted to the triple frequency crystal, the double frequency crystal and the third reflector in sequence, so that the triple frequency crystal outputs ultraviolet laser close to the end face of the second reflector. The present invention is helpful to improve the output power of ultraviolet laser.

Description

Technical Field

[0001] The invention relates to the technical field of solid lasers, and in particular to a high-power nanosecond ultraviolet laser. Background Art

[0002] Ultraviolet lasers have unique advantages such as short laser wavelength, high single photon energy, and the ability to focus to a very small spot. They have unique application value in many areas such as integrated circuit technology, fine laser processing, and life sciences. In the field of precision processing and manufacturing, solid nanosecond ultraviolet pulse lasers are a very important core light source, and in the field of high-precision cutting, high-power nanosecond ultraviolet light sources are indispensable. For example, in the photolithography process of integrated circuits, the shorter the wavelength of the ultraviolet laser, the higher the resolution that can be obtained; in laser fine processing, the single photon energy of ultraviolet light is large, which can directly destroy the molecular bonds or atomic connections of the material. The processing of the material is cold processing, and will not produce defects such as melting, debris, and cracks that often occur in hot processing, so the processing quality is extremely high.

[0003] The Chinese patent with publication number CN116780335A discloses an all-semiconductor ultraviolet laser with high beam quality and wide wavelength range, including an edge-emitting semiconductor excitation light source, a surface-emitting semiconductor gain medium, and a fundamental frequency oscillation and frequency conversion component, wherein the surface-emitting semiconductor gain medium and the fundamental frequency oscillation and frequency conversion component form a resonant cavity; the excitation light emitted by the edge-emitting semiconductor excitation light source can be projected onto the surface-emitting semiconductor gain medium; the surface-emitting semiconductor gain medium can absorb the photon energy of the excitation light emitted by the edge-emitting semiconductor excitation light source and generate stimulated radiation of the laser wavelength; the stimulated radiation forms a fundamental frequency laser oscillation in the resonant cavity, completes the frequency conversion, and finally outputs as ultraviolet laser. The all-semiconductor ultraviolet laser provided by the above scheme can only realize the frequency conversion rate of the wavelength of the light source alone, but cannot improve the output power of the output ultraviolet laser. Therefore, it is very necessary to provide a high-power nanosecond ultraviolet laser to improve the output power of the output ultraviolet laser. Summary of the invention

[0004] In view of this, the present invention proposes a high-power nanosecond ultraviolet laser, which increases the pump power of the ultraviolet laser through a double-end pumping method, and at the same time, the Q-switched device periodically shuts down the fundamental frequency resonance in the first resonant cavity to suppress the inversion population loss in the gain crystal and release energy to output a giant pulse with high power, so as to obtain a higher power ultraviolet laser output.

[0005] The present invention provides a high-power nanosecond ultraviolet laser, comprising a first pump source, a first pump mirror, a first gain crystal, a second gain crystal, a second pump mirror, a second pump source, a Q-switched device, a first reflector, a second reflector, a triple frequency crystal, a double frequency crystal and a third reflector, wherein:

[0006] The first pump source, the first pump mirror, the first gain crystal, the second gain crystal, the second pump mirror and the second pump source are sequentially arranged along the light emitting direction of the first pump source;

[0007] The first pump light emitted by the first pump source is transmitted through the first pump mirror in sequence to the first gain crystal, the second gain crystal and the second pump mirror, the first pump light is reflected by the second pump mirror, so that the reflected light of the second pump mirror is transmitted to the Q-switched device and the first reflector in sequence, the second pump light emitted by the second pump source is transmitted through the second pump mirror in sequence to the second gain crystal, the first gain crystal and the first pump mirror, the second pump light is reflected by the first pump mirror, so that the reflected light of the first pump mirror is reflected to the second reflector, and the first pump mirror, the second pump mirror and the first reflector constitute a first resonant cavity for generating fundamental frequency light oscillation, and the wavelength of the first pump light and the second pump light are the same;

[0008] The reflected light of the second reflector is transmitted to the tripled frequency crystal, the doubled frequency crystal and the third reflector in sequence, and the second reflector and the third reflector constitute a second resonant cavity that generates doubled frequency light oscillations, so that the tripled frequency crystal outputs ultraviolet laser close to the end face of the second reflector.

[0009] On the basis of the above technical solution, preferably, the distance between the first reflector and the second pump mirror is adjustable, a first beam waist arm length is formed between the first reflector and the second pump mirror, the distance between the first pump mirror and the second reflector is adjustable, a second beam waist arm length is formed between the first pump mirror and the second reflector, the distance between the second reflector and the tripled frequency crystal is adjustable, a third beam waist arm length is formed between the second reflector and the tripled frequency crystal, the distance between the tripled frequency crystal and the third reflector is adjustable, and a fourth beam waist arm length is formed between the tripled frequency crystal and the third reflector.

[0010] On the basis of the above technical solution, preferably, the high-power nanosecond ultraviolet laser meets the following conditions:

[0011] 1.2*L a <L b <1.8*L a ;

[0012] Among them, L a represents the first beam waist length, L b It represents the sum of the second beam arm length, the third beam arm length and the fourth beam arm length.

[0013] More preferably, a first coupling optical fiber and a first coupling mirror group are arranged between the first pump source and the first pump mirror, and a second coupling optical fiber and a second coupling mirror group are arranged between the second pump source and the second pump mirror.

[0014] More preferably, the core diameters of the first coupling optical fiber and the second coupling optical fiber are both 878.6 nm to 400 μm.

[0015] More preferably, the curvature radii of the first pump mirror and the second pump mirror are both 300-700 mm, the end face of the first pump mirror close to the first pump source is coated with a pump light high-transmittance film, the end face of the first pump mirror away from the first pump source is coated with a fundamental frequency light high-reflection film, the end face of the second pump mirror close to the second pump source is coated with a pump light high-transmittance film, and the end face of the second pump mirror away from the second pump source is coated with a fundamental frequency light high-reflection film.

[0016] Further preferably, both end faces of the first gain crystal and the second gain crystal are coated with a pump light high-transmittance film and a fundamental frequency light high-transmittance film, the first gain crystal and the second gain crystal are both Nd:YVO4 crystals, the concentrations of the first gain crystal and the second gain crystal are both 0.2% to 0.27%, and the sizes of the first gain crystal and the second gain crystal are both 3mm*3mm*16mm.

[0017] Further preferably, both end faces of the doubled frequency crystal and the tripled frequency crystal are coated with high-transmittance films for fundamental frequency light and doubled frequency light, the length of the doubled frequency crystal is 8 to 12 mm, the length of the tripled frequency crystal is 15 to 20 mm, and the end face of the tripled frequency crystal close to the second reflector is a bevel.

[0018] More preferably, the Q-switching device is an acousto-optic Q-switch or an electro-optic Q-switch, and the frequency of the Q-switching device is 0 to 200 kHz.

[0019] More preferably, it also includes a base and a water cooling system, wherein the first pump source, the first pump mirror, the first gain crystal, the second gain crystal, the second pump mirror, the second pump source, the Q-switched device, the first reflector, the second reflector, the triple frequency crystal, the double frequency crystal and the third reflector are all arranged on the base, and the temperature is controlled and the heat is dissipated by the water cooling system.

[0020] The high-power nanosecond ultraviolet laser provided by the present invention has the following beneficial effects compared with the prior art:

[0021] (1) A first resonant cavity for generating fundamental frequency light oscillation is formed by arranging a first pump mirror, a second pump mirror and a first reflector to realize oscillation excitation of fundamental frequency light, and a double-end pumping method is adopted to increase the pump power of the ultraviolet laser, so as to obtain a higher power fundamental frequency light output, and the fundamental frequency resonance in the first resonant cavity can be periodically turned off by a Q-switching device to suppress the inversion population loss in the gain crystal, and release energy to output a high-power giant pulse, and at the same time, the second reflector and the third reflector constitute a second resonant cavity for generating doubled frequency light oscillation, and the second resonant cavity receives the giant pulse released by the first resonant cavity, and performs frequency doubling and sum frequency through the doubled frequency crystal and the tripled frequency crystal in the second resonant cavity, so as to realize the output of high-power nanosecond ultraviolet light;

[0022] (2) The arm length relationship of high-power nanosecond ultraviolet laser satisfies 1.2*L a <L b <1.8*L a That is, the sum of the second beam waist arm length, the third beam waist arm length and the fourth beam waist arm length is adjusted by the first beam waist length, and the lengths of different beam waist arm lengths in the first resonant cavity and the second resonant cavity are changed to achieve the effect of adjusting the cavity lengths of the first resonant cavity and the second resonant cavity, thereby increasing the pulses of the pulsed laser generated by the oscillation of the first resonant cavity and the second resonant cavity, and at the same time compressing the laser spot at the frequency doubling crystal, thereby improving the conversion efficiency of pump light and fundamental frequency light. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the optical path of the high-power nanosecond ultraviolet laser provided by the present invention;

[0025] Figure 2 This is a 50W ultraviolet repetition power pulse width curve provided by the present invention.

[0026] Explanation of the accompanying drawings: 1. first pump source; 2. first pump mirror; 3. first gain crystal; 4. second gain crystal; 5. second pump mirror; 6. second pump source; 7. Q-switched device; 8. first reflector; 9. second reflector; 10. frequency tripling crystal; 11. frequency doubling crystal; 12. third reflector; 13. first coupling optical fiber; 14. first coupling mirror group; 15. second coupling optical fiber; 16. second coupling mirror group; 17. light absorbing tube. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, the present invention provides a high-power nanosecond ultraviolet laser, including a first pump source 1, a first pump mirror 2, a first gain crystal 3, a second gain crystal 4, a second pump mirror 5, a second pump source 6, a Q-switched device 7, a first reflector 8, a second reflector 9, a triple frequency crystal 10, a double frequency crystal 11 and a third reflector 12, wherein:

[0029] The first pump source 1 , the first pump mirror 2 , the first gain crystal 3 , the second gain crystal 4 , the second pump mirror 5 and the second pump source 6 are arranged in sequence along the light emitting direction of the first pump source 1 .

[0030] In this embodiment, the first pump source 1 and the second pump source 6 are both semiconductor lasers with the same wavelength of emitted light. In other embodiments, optical fiber lasers may also be used.

[0031] The first pump light emitted by the first pump source 1 is transmitted through the first pump mirror 2 to the first gain crystal 3, the second gain crystal 4 and the second pump mirror 5 in sequence. The first pump light is reflected by the second pump mirror 5, so that the reflected light of the second pump mirror 5 is transmitted to the Q-switched device 7 and the first reflector 8 in sequence. The second pump light emitted by the second pump source 6 is transmitted through the second pump mirror 5 to the second gain crystal 4, the first gain crystal 3 and the first pump mirror 2 in sequence. The second pump light is reflected by the first pump mirror 2, so that the reflected light of the first pump mirror 2 is reflected to the second reflector 9. The first pump mirror 2, the second pump mirror 5 and the first reflector 8 constitute a first resonant cavity for generating fundamental frequency light oscillations. The wavelength of the first pump light and the second pump light are the same.

[0032] In one example, a first coupling fiber 13 and a first coupling mirror group 14 are arranged between the first pump source 1 and the first pump mirror 2, and a second coupling fiber 15 and a second coupling mirror group 16 are arranged between the second pump source 6 and the second pump mirror 5. The core diameters of the first coupling fiber 13 and the second coupling fiber 15 are both 878.6 nm to 400 μm, and the first coupling mirror group 14 and the second coupling mirror group 16 are both coated with pump light anti-reflection films, so that the light output ratio of the first coupling mirror group 14 and the second coupling mirror group 16 is 1:2 to 1:4, and the first coupling mirror group 14 and the second coupling mirror group 16 each include at least two identical plano-convex lenses or two identical biconvex lenses.

[0033] In this embodiment, the curvature radius of the first pump mirror 2 and the second pump mirror 5 are both 300-700 mm, the end face of the first pump mirror 2 close to the first pump source 1 is coated with a pump light high-transmittance film, the end face of the first pump mirror 2 away from the first pump source 1 is coated with a fundamental frequency light high-reflection film, the end face of the second pump mirror 5 close to the second pump source 6 is coated with a pump light high-transmittance film, and the end face of the second pump mirror 5 away from the second pump source 6 is coated with a fundamental frequency light high-reflection film.

[0034] In this embodiment, both end surfaces of the first gain crystal 3 and the second gain crystal 4 are plated with a pump light high transmittance film and a fundamental frequency light high transmittance film, and the first gain crystal 3 and the second gain crystal 4 are both Nd:YVO4 crystals, so that the single-pass absorption rate of the pump light is 83% to 90%, the concentrations of the first gain crystal 3 and the second gain crystal 4 are both 0.2% to 0.27%, and the sizes of the first gain crystal 3 and the second gain crystal 4 are both 3mm*3mm*16mm.

[0035] It is understandable that the first gain crystal 3 and the second gain crystal 4 can also be any one of Yb:YAG crystal, Nd:YLF crystal, Nd:GdVO4 crystal, Nd:YAG crystal, and Nd:YAP crystal. Specifically, the first pump source 1 and the second pump source 6 that are arranged relatively generate pump light, and the pump light spot is coupled into the first gain crystal 3 and the second gain crystal 4 through the correspondingly arranged coupling optical fiber and coupling lens group, and the first gain crystal 3 and the second gain crystal 4 are double-ended pumped to generate fundamental frequency light, so that the fundamental frequency light oscillates in the first resonant cavity.

[0036] In this embodiment, the pump light emitted by the first pump source 1 is coupled into the first resonant cavity through the first coupling optical fiber 13 and the first coupling lens group through the first coupling mirror, and the pump light emitted by the second pump source 6 is coupled into the first resonant cavity through the second coupling optical fiber 15 and the second coupling lens group through the second coupling mirror. The pump light is absorbed by the first gain crystal 3 and the second gain crystal 4 and oscillates back and forth between the first coupling mirror and the second coupling mirror to form fundamental frequency light. At the same time, due to the reflection effect of the second coupling mirror, part of the pump light and fundamental frequency light enter the Q-switching device 7 and then reflect through the first reflector 8 to repeatedly oscillate between the first coupling mirror and the second coupling mirror. The Q-switching device 7 periodically shuts off the resonance of the fundamental frequency light in the cavity, suppresses the inversion population loss of the first gain crystal 3 and the second gain crystal 4, so as to achieve the effect of energy storage. And under the reflection effect of the first coupling mirror and the energy release of the first resonant cavity, the first coupling mirror transmits the giant pulse generated in the first resonant cavity to the second resonant cavity.

[0037] Preferably, the Q-switching device 7 is an acousto-optic Q-switch or an electro-optic Q-switch, and the frequency of the Q-switching device 7 is 0 to 200 kHz. Specifically, the pump light emitted by the first pump source 1 and the second pump source 6 is coupled to the fundamental frequency light in the first gain crystal 3 and the second gain crystal 4 through the correspondingly arranged coupling optical fiber and coupling lens group, and is modulated by the acousto-optic Q-switching switch or the electro-optic Q-switching switch to achieve high-power and high-repetition-frequency fundamental frequency light operation.

[0038] The reflected light of the second reflector 9 is transmitted to the tripled frequency crystal 10, the doubled frequency crystal 11 and the third reflector 12 in sequence, and the second reflector 9 and the third reflector 12 constitute a second resonant cavity for generating doubled frequency light oscillations, so that the tripled frequency crystal 10 outputs ultraviolet laser near the end face of the second reflector 9.

[0039] In this embodiment, both end faces of the doubled frequency crystal 11 and the tripled frequency crystal 10 are coated with high-transmittance films for fundamental frequency light and high-transmittance films for doubled frequency light. The length of the doubled frequency crystal 11 is 8 to 12 mm, and the length of the tripled frequency crystal 10 is 15 to 20 mm. The end face of the tripled frequency crystal 10 close to the second reflector 9 is a bevel, and the angle of the face is 57.4° to achieve separation of fundamental frequency horizontally polarized light, doubled frequency horizontally polarized light, and doubled frequency vertically polarized light.

[0040] Among them, the double frequency adopts the first type of phase matching o+o→e, and the triple frequency adopts the second type of phase matching o+e→o. In the second resonant cavity, 1064nm is horizontally polarized light (i.e., fundamental frequency light), 532nm is vertically polarized light (i.e., double frequency light), and 355nm is horizontally polarized light. The corresponding refractive indices of the fundamental frequency horizontal polarized light, double frequency vertical polarized light, and double frequency horizontal polarized light in the triple frequency crystal 10 are 1.5656, 1.6136, and 1.5973, respectively. It is further calculated that the splitting angles of the fundamental frequency horizontal polarized light, double frequency vertical polarized light, and double frequency horizontal polarized light are 57.5115°, 60.3844°, and 59.3816°, respectively, that is, the fundamental frequency horizontal polarized light, double frequency vertical polarized light, and double frequency horizontal polarized light can be separated when the layout angle of the triple frequency crystal 10 is 57.4°. In addition, a light absorbing tube 17 is arranged in the light emitting direction of the frequency-doubled vertically polarized light (532 nm) to absorb incoherent light beams.

[0041] It can be understood that the doubled frequency crystal 11 and the tripled frequency crystal 10 can be any one of KTP, PPLN, LBO, and BBO, but are not limited to this. They can be selected according to actual needs and adopt critical or non-critical phase matching. The size of the first gain crystal 3 and the second gain crystal 4 is 3mm×3mm×15mm or 3mm×3mm×12mm or other sizes. The two end surfaces are respectively coated with a high-transmittance film for fundamental frequency light and a high-transmittance film for doubled frequency light. The temperature is controlled by a semiconductor refrigeration sheet, and the temperature control accuracy is better than ±0.1°C.

[0042] In this embodiment, the distance between the first reflector 8 and the second pump mirror 5 is adjustable, and a first waist arm length is formed between the first reflector 8 and the second pump mirror 5. The distance between the first pump mirror 2 and the second reflector 9 is adjustable, and a second waist arm length is formed between the first pump mirror 2 and the second reflector 9. The distance between the second reflector 9 and the third harmonic generation crystal 10 is adjustable, and a third waist arm length is formed between the second reflector 9 and the third harmonic generation crystal 10. The distance between the third harmonic generation crystal 10 and the third reflector 12 is adjustable, and a fourth waist arm length is formed between the third harmonic generation crystal 10 and the third reflector 12.

[0043] The high-power nanosecond ultraviolet laser satisfies the following conditions:

[0044] 1.2*La < Lb < 1.8*La

[0045] Wherein, La represents the first waist arm length, and Lb represents the sum of the second waist arm length, the third waist arm length, and the fourth waist arm length.

[0046] The arm length relationship of the high-power nanosecond ultraviolet laser satisfies 1.2*La < Lb < 1.8*La, that is, the sum of the second waist arm length, the third waist arm length, and the fourth waist arm length is adjusted by the first waist length. By changing the lengths of different waist arm lengths in the first resonant cavity and the second resonant cavity, the effect of adjusting the cavity lengths of the first resonant cavity and the second resonant cavity is achieved, thereby increasing the width of the pulsed laser generated by oscillation in the first resonant cavity and the second resonant cavity. At the same time, the laser spot at the frequency doubling crystal is compressed, and the conversion efficiency of the pump light and the fundamental frequency light is improved.

[0047] Working principle: The symmetrically arranged first pump source 1 and second pump source 6 transmit pump light through the corresponding first coupling optical fiber 13 and second coupling optical fiber 15, and couple the pump light to the first coupling mirror and the second coupling mirror through the first coupling lens and the second coupling lens group, and at the same time transfer energy to the first gain crystal 3 and the second gain crystal 4 to produce a population inversion, so that the first gain crystal 3 and the second gain crystal 4 spontaneously emit and generate a laser with a wavelength of 1064nm, wherein the photons transmitted along the optical axis are reflected in the resonant cavity formed by the first coupling mirror, the second coupling mirror, the first reflector 8, the second reflector 9 and the third reflector 12, and are amplified and form laser when passing through the first gain crystal 3 and the second gain crystal 4, and the Q-switching device 7 periodically shuts off the 1064nm resonance in the cavity, suppresses the inversion population loss in the first gain crystal 3 and the second gain crystal 4, and stores energy. The energy stored in the resonant cavity is released after a certain period of time to generate a giant pulse, which is frequency doubled and summed by the doubled frequency crystal 11 and the tripled frequency crystal 10 to obtain 532nm and 355nm lasers respectively. Due to the refractive index of the laser with a wavelength of 1064nm, the laser with a wavelength of 532nm and the laser with a wavelength of 355nm in the tripled frequency crystal 10, the laser with a wavelength of 1064nm, the laser with a wavelength of 532nm and the laser with a wavelength of 355nm are emitted at different angles, resulting in separation.

[0048] A first resonant cavity for generating fundamental frequency light oscillations is formed by setting a first pump mirror 2, a second pump mirror 5 and a first reflector 8 to realize oscillation excitation of fundamental frequency light, and a double-end pumping method is adopted to increase the pumping power of the ultraviolet laser, so as to obtain a higher power fundamental frequency light output, and the fundamental frequency resonance in the first resonant cavity can be periodically shut down by a Q-switching device 7 to suppress the inversion population loss in the gain crystal, and at the same time, the second reflector 9 and the third reflector 12 constitute a second resonant cavity for generating doubled frequency light oscillations, and the second resonant cavity receives the giant pulse released by the first resonant cavity, and performs frequency doubling and sum frequency through a doubled frequency crystal 11 and a tripled frequency crystal 10 in the second resonant cavity, so as to realize the output of high-power nanosecond ultraviolet light.

[0049] like Figure 2 As shown, Figure 2 The 50W UV repetition power pulse width curve is shown in the figure. The maximum UV pulse width provided by this solution is 46ns, the minimum UV pulse width is 16.1ns, the maximum UV power is 54W, and the minimum UV power is 17W. It can be understood that when the UV repetition rate is between 50 and 200kHz, the UV power of the high-power nanosecond UV laser gradually increases from 21W to 54W, meeting the high-power requirement of the UV laser.

[0050] Preferably, it also includes a base and a water cooling system, wherein the first pump source 1, the first pump mirror 2, the first gain crystal 3, the second gain crystal 4, the second pump mirror 5, the second pump source 6, the Q-switched device 7, the first reflector 8, the second reflector 9, the triple frequency crystal 10, the double frequency crystal 11 and the third reflector 12 are all arranged on the base, and the temperature is controlled and the heat is dissipated by the water cooling system, so that the laser can work normally and efficiently.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-power nanosecond ultraviolet laser, characterized in that: The invention comprises a first pump source (1), a first pump mirror (2), a first gain crystal (3), a second gain crystal (4), a second pump mirror (5), a second pump source (6), a Q-switched device (7), a first reflector (8), a second reflector (9), a frequency tripling crystal (10), a frequency doubling crystal (11) and a third reflector (12), wherein: The first pump source (1), the first pump mirror (2), the first gain crystal (3), the second gain crystal (4), the second pump mirror (5) and the second pump source (6) are arranged in sequence along the light emitting direction of the first pump source (1); The first pump light emitted by the first pump source (1) is transmitted through the first pump mirror (2) to the first gain crystal (3), the second gain crystal (4) and the second pump mirror (5) in sequence; the first pump light is reflected by the second pump mirror (5), so that the reflected light of the second pump mirror (5) is transmitted to the Q-switching device (7) and the first reflector (8) in sequence; the second pump light emitted by the second pump source (6) is transmitted through the second pump mirror (5) to the second gain crystal (4), the first gain crystal (3) and the first pump mirror (2) in sequence; the second pump light is reflected by the first pump mirror (2), so that the reflected light of the first pump mirror (2) is reflected to the second reflector (9); the first pump mirror (2), the second pump mirror (5) and the first reflector (8) constitute a first resonant cavity for generating fundamental frequency light oscillation; the wavelength of the first pump light and the second pump light are the same; The distance between the first reflector (8) and the second pump mirror (5) is adjustable, and a first beam waist arm length is formed between the first reflector (8) and the second pump mirror (5); the distance between the first pump mirror (2) and the second reflector (9) is adjustable, and a second beam waist arm length is formed between the first pump mirror (2) and the second reflector (9); the distance between the second reflector (9) and the triple frequency crystal (10) is adjustable, and a third beam waist arm length is formed between the second reflector (9) and the triple frequency crystal (10); the distance between the triple frequency crystal (10) and the third reflector (12) is adjustable, and a fourth beam waist arm length is formed between the triple frequency crystal (10) and the third reflector (12); The high-power nanosecond ultraviolet laser meets the following conditions: 1.2×La <Lb<1.8×La Wherein, La represents the first beam waist arm length, and Lb represents the sum of the second beam waist arm length, the third beam waist arm length, and the fourth beam waist arm length; The reflected light of the second reflector (9) is transmitted to the triple frequency crystal (10), the double frequency crystal (11) and the third reflector (12) in sequence, and the second reflector (9) and the third reflector (12) form a second resonant cavity for generating double frequency light oscillations, so that the triple frequency crystal (10) outputs ultraviolet laser light near the end face of the second reflector (9).

2. The high-power nanosecond ultraviolet laser according to claim 1, characterized in that: A first coupling optical fiber (13) and a first coupling mirror group (14) are arranged between the first pump source (1) and the first pump mirror (2), and a second coupling optical fiber (15) and a second coupling mirror group (16) are arranged between the second pump source (6) and the second pump mirror (5).

3. The high-power nanosecond ultraviolet laser according to claim 2, characterized in that: The core diameters of the first coupling optical fiber (13) and the second coupling optical fiber (15) are both 878.6 nm to 400 μm.

4. The high-power nanosecond ultraviolet laser according to claim 1, characterized in that: The curvature radii of the first pump mirror (2) and the second pump mirror (5) are both 300-700 mm, the end face of the first pump mirror (2) close to the first pump source (1) is coated with a pump light high transmittance film, the end face of the first pump mirror (2) away from the first pump source (1) is coated with a fundamental frequency light high reflection film, the end face of the second pump mirror (5) close to the second pump source (6) is coated with a pump light high transmittance film, and the end face of the second pump mirror (5) away from the second pump source (6) is coated with a fundamental frequency light high reflection film.

5. The high-power nanosecond ultraviolet laser according to claim 1, characterized in that: Both end surfaces of the first gain crystal (3) and the second gain crystal (4) are plated with a pump light high transmittance film and a fundamental frequency light high transmittance film, the first gain crystal (3) and the second gain crystal (4) are both Nd:YVO4 crystals, the concentrations of the first gain crystal (3) and the second gain crystal (4) are both 0.2% to 0.27%, and the sizes of the first gain crystal (3) and the second gain crystal (4) are both 3 mm×3 mm×16 mm.

6. The high-power nanosecond ultraviolet laser according to claim 1, characterized in that: Both end faces of the double frequency crystal (11) and the triple frequency crystal (10) are plated with a high transmittance film for fundamental frequency light and a high transmittance film for double frequency light; the length of the double frequency crystal (11) is 8 to 12 mm, the length of the triple frequency crystal (10) is 15 to 20 mm, and the end face of the triple frequency crystal (10) close to the second reflector (9) is an inclined surface.

7. The high-power nanosecond ultraviolet laser according to claim 1, characterized in that: The Q-switching device (7) is an acousto-optic Q-switch or an electro-optic Q-switch, and the frequency of the Q-switching device (7) is 0-200 kHz.

8. The high-power nanosecond ultraviolet laser according to any one of claims 1 to 7, characterized in that: It also includes a base and a water cooling system, wherein the first pump source (1), the first pump mirror (2), the first gain crystal (3), the second gain crystal (4), the second pump mirror (5), the second pump source (6), the Q-switched device (7), the first reflector (8), the second reflector (9), the triple frequency crystal (10), the double frequency crystal (11) and the third reflector (12) are all arranged on the base, and the water cooling system is used for temperature control and heat dissipation.

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