A high power ultraviolet laser

Abstract

The application discloses a high-power ultraviolet laser, and relates to the technical field of lasers.The application realizes the power breakthrough of fundamental light, simultaneously completes the accurate preprocessing of the polarization state, and realizes the high-power ultraviolet laser output.The laser comprises a seed light module, a first light splitting prism, a second full reflection mirror, a first double-pass amplification module, a first focusing lens, a first 1 / 2 wave plate, a second double-pass amplification module, a fifth full reflection mirror, a second focusing lens, a second 1 / 2 wave plate, a beam combining prism, a frequency doubling enhancement module and a second light splitting prism; the fundamental light output by the seed light module is split into orthogonally polarized lights through the first light splitting prism, the first light passes through the second full reflection mirror, the first double-pass amplification module, the first focusing lens and the first 1 / 2 wave plate in sequence; the second light passes through the second double-pass amplification module, the fifth full reflection mirror, the second focusing lens and the second 1 / 2 wave plate in sequence, the two lights are combined, and then the high-power ultraviolet laser is output after passing through the frequency doubling enhancement module and the second light splitting prism.

Description

Technical Field

[0001] This application relates to the field of laser technology, and more particularly to a high-power ultraviolet laser. Background Technology

[0002] Ultraviolet pulsed lasers have shown great application value in semiconductor wafer dicing, laser-induced fluorescence spectroscopy, biomedical photochemical synthesis, and micro / nano fabrication. Currently, the typical technical approach to obtaining ultraviolet lasers in this wavelength range is through the use of praseodymium-doped lasers (Pr). 3+ Ion-based gain media (such as Pr:YAP or Pr:YLF) generate a red fundamental frequency wave around 622nm, which is then combined with a nonlinear frequency doubling crystal (such as BBO or LBO) for second harmonic generation (SHG). Among these, Pr:YAP crystal, due to its orthorhombic crystal structure resulting in high thermal conductivity and high stimulated emission cross-section under 488nm blue semiconductor pumping, has become the preferred gain medium for achieving high-power red light output.

[0003] However, in the process of moving towards higher power ultraviolet laser output, existing high-power ultraviolet laser technologies have the following problems: First, there is the thermal load bottleneck of the gain medium. In a single-channel oscillating amplification structure, the energy density of the pump source must be continuously increased to improve the output power. However, due to the quantum defect in the Pr:YAP crystal, high-power pumping will produce severe anisotropic thermal lensing and thermally induced birefringence within the crystal. When the pump power exceeds a certain threshold, the rapid temperature rise at the crystal center will cause a rapid deterioration in beam quality and may even lead to thermal cracking of the crystal. Although the traditional cascade amplification scheme (MOPA) can further increase the energy, the cumulative effect of the thermal distortion of the seed light from the previous stage on the subsequent amplifier makes it difficult to maintain the stability of the final output fundamental frequency light at high power.

[0004] Secondly, there is the challenge of polarization matching during high-power frequency doubling. To achieve higher frequency doubling efficiency and wider receiving bandwidth, high-power ultraviolet laser systems often employ type II phase matching with nonlinear crystals. According to the principles of nonlinear optics, type II phase matching requires that the incident fundamental light must simultaneously contain mutually perpendicular polarization components (i.e., o-ray and e-ray), and their power ratio must be strictly balanced to maximize conversion efficiency. However, in traditional high-power laser systems, generating a fundamental light beam with both extremely high total power and precisely controlled, power-balanced orthogonal polarization is extremely difficult in engineering. A common approach is to forcibly rotate the polarization direction of a single high-power beam using a waveplate, but this easily leads to polarization extinction ratio degradation and thermal damage to the waveplate at extremely high power, making it difficult to maintain stable type II phase matching conditions under high-power operation.

[0005] In summary, how to achieve a breakthrough in the power of fundamental frequency light and simultaneously complete the precise preprocessing of the polarization state to match the requirements of efficient frequency doubling has become a problem to be solved in the field of high-performance ultraviolet laser technology. Summary of the Invention

[0006] The embodiments of this application provide a high-power ultraviolet laser, which achieves a breakthrough in the power of the fundamental frequency light through a local oscillator + dual-path parallel two-pass amplification structure, and simultaneously completes the precise preprocessing of the polarization state to match the requirements of efficient frequency doubling, thereby realizing high-power and high-stability ultraviolet laser output.

[0007] To achieve the above objectives, embodiments of this application provide a high-power ultraviolet laser, including a seed light module, a first beam splitter, a second total reflection mirror, a first two-way amplification module, a first focusing lens, a first half-wave plate, a second two-way amplification module, a fifth total reflection mirror, a second focusing lens, a second half-wave plate, a beam combiner prism, a frequency doubling enhancement module, and a second beam splitter prism. The fundamental frequency light output from the seed light module is split into two orthogonally polarized fundamental frequency beams by the first beam splitter prism. The first fundamental frequency beam is reflected by the second total reflection mirror and then sequentially passes through the first two-way amplification module. The system consists of a first focusing lens and a first half-wave plate; the second fundamental frequency light passes through a second two-way amplification module and is then reflected by a fifth total reflection mirror before passing through the second focusing lens and the second half-wave plate in sequence; the first two-way amplification module enables two-way traveling-wave amplification of the first seed light; the second two-way amplification module enables two-way traveling-wave amplification of the second seed light; the output light from the first half-wave plate and the output light from the second half-wave plate simultaneously enter the beam combiner prism; the combined fundamental frequency light passes through a frequency doubling enhancement module and a second beam splitter prism in sequence before outputting a high-power ultraviolet laser.

[0008] Furthermore, the seed light module includes a 488nm semiconductor laser, a coupling lens group, a first total reflection mirror, a first Pr:YAP crystal, and an output mirror arranged sequentially; the optical surface of the first total reflection mirror is coated with a dielectric film that is highly transparent to the 488nm pump light and highly reflective to the 622nm fundamental frequency light; the first total reflection mirror and the output mirror constitute the seed local oscillator resonant cavity.

[0009] Furthermore, the first beam splitter is a polarizing beam splitter; the beam combiner is a polarizing beam combiner.

[0010] Furthermore, the first two-way amplification module includes a first polarizing beam splitter, a first pump module, a first quarter-wave plate, and a third total reflection mirror arranged sequentially along the direction of light propagation; the first pump module includes a first pump LD bar pair; the operating wavelength of the first pump LD bar pair is 488nm; and a second Pr:YAP crystal is disposed within the first pump LD bar pair.

[0011] Furthermore, the second double-pass amplification module has the same structure as the first double-pass amplification module, but its setting direction is opposite and it is staggered.

[0012] Furthermore, the second two-way amplification module includes a second polarizing beam splitter, a second pump module, a second quarter-wave plate, and a fourth total reflection mirror arranged sequentially along the direction of light propagation; the second pump module includes a second pump LD bar pair; the operating wavelength of the second pump LD bar pair is 488nm; and a third Pr:YAP crystal is disposed within the second pump LD bar pair.

[0013] Furthermore, the fast axis / slow axis of the first and second quarter wave plates are at a 45° angle to the polarization direction of the incident light, which enables the incident linearly polarized light to become circularly polarized light after passing through once, and the polarization state to rotate 90° after passing through twice, thereby achieving polarization state control and optical path isolation for double-pass amplification.

[0014] Furthermore, both ends of the first, second, and third Pr:YAP crystals are coated with an antireflective film that allows high transmission of 622nm fundamental frequency light.

[0015] Furthermore, the frequency doubling enhancement module includes an enhancement cavity input mirror, a BBO crystal, and an enhancement cavity output mirror; the enhancement cavity input mirror and the enhancement cavity output mirror constitute a linear resonant cavity, and the BBO crystal is placed inside the resonant cavity; the enhancement cavity input mirror is coated with a dielectric film that is highly transparent to 622nm fundamental frequency light; the optical surface of the enhancement cavity output mirror is coated with a dielectric film that is highly reflective to 622nm fundamental frequency light and highly transparent to 311nm ultraviolet light; the two ends of the BBO crystal are coated with dual-band anti-reflection films for 622nm fundamental frequency light and 311nm ultraviolet light.

[0016] Furthermore, the second beam splitter uses the difference in refractive index of light of different wavelengths to spatially separate the 622nm fundamental frequency light from the 311nm ultraviolet light.

[0017] This application has the following advantages over the prior art: The high-power ultraviolet laser in this embodiment employs a local oscillator + dual-path parallel two-pass amplification structure. A high-beam-quality 622nm fundamental frequency seed light is output from the seed local oscillator resonant cavity. The seed light is then amplified in parallel power by two symmetrically configured parallel two-pass amplification units, overcoming the gain saturation limitation of single-stage amplification and significantly increasing the output power of the fundamental frequency light. Simultaneously, it avoids the thermal lensing distortion problem caused by single-path high-power amplification, ensuring stable beam quality during amplification. Furthermore, a polarization splitting-combining optical path structure using a beam splitter prism and a beam combiner prism is employed. The beam splitter prism splits the seed light into two orthogonally polarized beams, which are then guided into the amplification branches. After symmetrical amplification, two amplified beams with equal power and mutually perpendicular polarization states are obtained. These beams are then combined coaxially without loss using a beam combiner prism. The resulting combined beam perfectly matches the type II phase-matching condition of a polarized BBO crystal, significantly improving the nonlinear frequency doubling conversion efficiency and solving the problems of low frequency doubling efficiency and limited power increase in traditional single-polarized fundamental frequency light. Ultimately, this achieves high-power, high-stability 311nm ultraviolet laser output. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the planar structure of a high-power ultraviolet laser according to an embodiment of this application. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0022] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation", "connection" and "joining" should be interpreted broadly, for example, they can refer to fixed connections, detachable connections, or integral connections; those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0023] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" can explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0024] Reference Figure 1 This application provides a high-power ultraviolet laser, including a seed light module, a first beam splitter 6, a second total reflection mirror 7, a first two-way amplification module, a first focusing lens 14, a first half-wave plate 15, a second two-way amplification module, a fifth total reflection mirror 23, a second focusing lens 24, a second half-wave plate 25, a beam combiner 16, a frequency doubling enhancement module, and a beam splitter 29.

[0025] The seed light module includes a 488nm semiconductor laser 1, a coupling lens group 2, a first total reflection mirror 3, a first Pr:YAP crystal 4, and an output mirror 5 arranged sequentially.

[0026] The 488nm semiconductor laser 1 is a semiconductor pump source with fiber-coupled output. Its output wavelength matches the absorption peak of the first Pr:YAP crystal 4, which is used to provide pump energy for the local oscillator and output collimated pump beam.

[0027] The first total reflection mirror 3 is the rear cavity mirror of the seed local oscillator resonant cavity, and its optical surface is coated with a dielectric film that is highly transparent to 488nm pump light and highly reflective to 622nm fundamental frequency light. The output mirror 5 is the front output coupling mirror of the seed local oscillator resonant cavity, and its optical surface is coated with a dielectric film that partially transmits and partially reflects 622nm fundamental frequency light. Together with the first total reflection mirror 3, they form a stable resonant cavity structure.

[0028] The first Pr:YAP crystal 4 is placed in the resonant cavity formed by the first total reflection mirror 3 and the output mirror 5 to generate 622nm fundamental frequency seed light. Both ends of the first Pr:YAP crystal 4 are coated with an anti-reflection film that is highly transparent to 622nm fundamental frequency light.

[0029] Therefore, the output wavelength of the 488nm semiconductor laser 1 matches the strongest absorption peak of the first Pr:YAP crystal 4. After the output beam is shaped by the coupling lens group 2, the mode matches the fundamental mode oscillation mode of the seed local resonant cavity, ensuring efficient coupling of the pump light and high beam quality output of the fundamental frequency light.

[0030] The fundamental frequency light output from the seed light module is split into two orthogonally polarized fundamental frequency beams by the first beam splitter prism 6. The first fundamental frequency beam is refracted by the second total reflection mirror and then passes sequentially through the first double-pass amplification module, the first focusing lens 14, and the first half-wave plate 15. The second fundamental frequency beam passes through the second double-pass amplification module and is then reflected by the fifth total reflection mirror 23 before passing sequentially through the second focusing lens 24 and the second half-wave plate 25.

[0031] The first beam splitter 6 is a polarizing beam splitter. Its placement angle makes the transmitted light and reflected light form a 90° angle, which can split the incident fundamental frequency seed light into two orthogonally polarized beams according to a preset ratio (such as 1:1). This provides polarization-matched incident light for subsequent dual-path parallel amplification and polarization beam combining. This can effectively disperse the heat load under high-power pumping conditions and form a power enhancement architecture of "local oscillator + parallel amplification".

[0032] The first two-way amplification module enables two-way traveling-wave amplification of the first seed beam. The second two-way amplification module enables two-way traveling-wave amplification of the second seed beam. The second two-way amplification module has the same structure as the first two-way amplification module, but its orientation is opposite and it is staggered. The Pr:YA crystal, pump LD bar pair, quarter-wave plate, and optical path length in both two two-way amplification modules are kept consistent to ensure that the power of the two amplified beams is equal and the polarization states are strictly orthogonal, satisfying the requirements of beam combining and type II phase matching.

[0033] Specifically, the first two-way amplification module includes a first polarizing beam splitter 8, a first pump module 10, a first quarter-wave plate 12, and a third total reflection mirror 13 arranged sequentially along the light propagation direction. The first pump module 10 includes a first pump LD bar pair. The operating wavelength of the first pump LD bar pair is 488nm. A second Pr:YAP crystal 9 is disposed within the first pump LD bar pair, and both ends of the second Pr:YAP crystal 9 are coated with anti-reflection films that provide high transmittance for 622nm fundamental frequency light. The first pump LD bar pair provides uniform pump energy to the second Pr:YAP crystal 9, reducing crystal thermal distortion and improving amplification efficiency and beam quality. The first two-way amplification module enables the seed light to pass through the amplifying crystal (second Pr:YAP crystal 9) twice to achieve two-way amplification, and utilizes the polarization rotation principle to export the amplified high-power fundamental frequency light through the first polarizing beam splitter 8.

[0034] The second two-way amplification module includes a second polarizing beam splitter 17, a second pump module 18, a second quarter-wave plate 21, and a fourth total reflection mirror 22 arranged sequentially along the light propagation direction. The second pump module 18 includes a second pump LD bar pair. The operating wavelength of the second pump LD bar pair is 488 nm. A third Pr:YAP crystal 19 is disposed within the second pump LD bar pair. Both ends of the third Pr:YAP crystal 19 are coated with antireflective films that provide high transmittance to 622 nm fundamental frequency light.

[0035] The fast / slow axis of the first quarter wave plate 12 and the second quarter wave plate 21 are at a 45° angle to the polarization direction of the incident light, which enables the incident linearly polarized light to become circularly polarized light after passing through once, and the polarization state to rotate 90° after passing through twice, thus realizing polarization state control and optical path isolation for double-pass amplification.

[0036] Both the first half-wave plate 15 and the second half-wave plate 25 are used to fine-tune the polarization direction of the amplified light in the corresponding branch, ensuring that the polarization states of the two beams incident on the beam combiner prism 16 are strictly orthogonal, thus achieving lossless power superposition during the beam combining process. That is, one beam is P-polarized and the other is S-polarized, and the power is equal through the previous beam splitting and gain control.

[0037] The beam combiner prism 16 is a polarization beam combiner prism that can combine two amplified beams with perpendicular polarization states and equal power (the output light from the first half-wave plate 15 and the output light from the second half-wave plate 25) into a single coaxial fundamental frequency beam. The output combined beam directly satisfies the type II phase matching condition of the BBO crystal 27. This "split-combination structure" design not only superimposes power but also optimizes the polarization distribution during the frequency doubling process, which is beneficial for obtaining high-power ultraviolet light in subsequent processes.

[0038] The frequency doubling enhancement module includes an input mirror 26, a BBO crystal 27, and an output mirror 28. The input mirror 26 and the output mirror 28 form a linear resonant cavity, and the BBO crystal 27 is placed inside the resonant cavity. The input mirror 26 is coated with a dielectric film that is highly transparent to 622nm fundamental frequency light, and the optical surface of the output mirror 28 is coated with a dielectric film that is highly reflective to 622nm fundamental frequency light and highly transparent to 311nm ultraviolet light. The two end faces of the BBO crystal 27 are coated with dual-band anti-reflection films for 622nm fundamental frequency light and 311nm ultraviolet light.

[0039] BBO crystal 27 is a high-frequency doubling efficiency crystal placed within an external enhancement cavity consisting of an input mirror and an output mirror. Through the accumulation of circulating power within the cavity, it improves the conversion efficiency from 622nm fundamental frequency light to 311nm ultraviolet light. BBO crystal 27 operates in type II phase-matched mode, directly converting 622nm fundamental frequency light to 311nm ultraviolet light through nonlinear frequency doubling, without undergoing multiple cascaded frequency conversions.

[0040] The light emitted from the output mirror 28 of the enhancement cavity enters the second beam splitter 29. The second beam splitter 29 is a dispersive beam splitting element placed at the end of the system. It utilizes the difference in refraction or reflection characteristics of different wavelengths on the surface of the medium to spatially separate the 311nm ultraviolet light from the residual 622nm fundamental frequency light, resulting in high-purity ultraviolet output.

[0041] The working principle of this application embodiment is as follows: The pump light emitted by the 488nm semiconductor laser 1 is first shaped and focused by the coupling lens group 2, and then incident on the first Pr:YAP crystal 4 through the first total reflection mirror 3. The first total reflection mirror 3 and the output mirror 5 form a seed local oscillator resonant cavity. The pump light excites the gain medium (first Pr:YAP crystal 4) to generate 622nm fundamental frequency light. After oscillation in the resonant cavity, the high beam quality fundamental frequency seed light is output by the output mirror 5, thus completing the generation of the local oscillator seed light.

[0042] After the seed light is incident on the first beam splitter 6, it is split into two orthogonally polarized beams, which are respectively guided into two parallel double-pass amplification branches (the first double-pass amplification module and the second double-pass amplification module) to realize the acquisition of high-power fundamental frequency light by local oscillator + parallel amplification.

[0043] The first beam is refracted by the second total reflection mirror 7 and then incident on the second Pr:YAP crystal 9. It is amplified by the first pump LD bar and then amplified by a single pass. The amplified beam passes through the first quarter wave plate 12 and is reflected by the third total reflection mirror 13. It passes through the first quarter wave plate 12 again to complete a 90° polarization rotation. At the same time, it is amplified twice by the second Pr:YAP crystal 9 and finally reflected by the first polarizing beam splitter 8 and output to the beam combiner prism 16.

[0044] The second beam is incident on the second Pr:YAP crystal 19 via the second polarizing beam splitter 17. After being pumped by the second pump LD bar to complete a single-pass amplification, the amplified beam passes through the second quarter-wave plate 21 and is reflected by the fourth total reflection mirror 22. It then passes through the second quarter-wave plate 21 again to complete a 90° polarization rotation. At the same time, it passes through the second Pr:YAP crystal 19 a second time to complete a double-pass amplification. Finally, it is folded by the fifth total reflection mirror 23 and output to the beam combiner prism 16.

[0045] Two amplified orthogonally polarized beams are shaped by the first focusing lens 14 and the second focusing lens 24, respectively. After the polarization direction is finely adjusted by the first half-wave plate 5 and the second half-wave plate 25, they are incident on the beam combining prism 16, completing the coaxial beam combining of beams with perpendicular polarization phases and equal power. This realizes the splitting-combining optical path design of the first beam splitter prism 6 + beam combining prism 16. The fundamental frequency light after beam combining enters the frequency doubling enhancement cavity composed of the enhancement cavity input mirror 26 and the enhancement cavity output mirror 28 through the enhancement cavity input mirror 26. The BBO crystal 27 in the cavity converts the 622nm fundamental frequency light into 311nm ultraviolet laser through the second harmonic effect. Finally, the ultraviolet laser is transmitted and output through the enhancement cavity output mirror 28. The remaining fundamental frequency light and ultraviolet light are separated by the beam splitter prism 29 to obtain pure ultraviolet laser output.

[0046] By adjusting the pump power and polarization control elements of the two amplification branches, precise power matching of the two amplified beams can be achieved, ensuring a high degree of consistency between the polarization state of the combined beam and the phase matching requirements of the BBO crystal 27. Compared to traditional single-stage amplification structures, this embodiment significantly improves the fundamental frequency output power and greatly enhances the frequency doubling conversion efficiency, resulting in higher and more stable ultraviolet laser output power. It also enables wide-range power control to adapt to different application scenarios.

[0047] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high-power ultraviolet laser, characterized in that, It includes a seed light module, a first beam splitter prism, a second total reflection mirror, a first two-way magnification module, a first focusing lens, a first half-wave plate, a second two-way magnification module, a fifth total reflection mirror, a second focusing lens, a second half-wave plate, a beam combiner prism, a frequency doubling enhancement module, and a second beam splitter prism; The fundamental frequency light output by the seed light module is split into two orthogonally polarized fundamental frequency lights by the first beam splitter. The first fundamental frequency light is reflected by the second total reflection mirror and then passes through the first double-pass amplification module, the first focusing lens and the first 1 / 2 wave plate in sequence. The second fundamental frequency light passes through the second double-pass amplification module, is reflected by the fifth total reflection mirror, and then passes through the second focusing lens and the second half-wave plate in sequence. The first two-way amplification module can realize two-way traveling wave amplification of the first seed light; The second two-way amplification module can realize two-way traveling wave amplification of the second seed light; The light emitted from the first half-wave plate and the light emitted from the second half-wave plate enter the beam combiner prism simultaneously. After beam combining, the fundamental frequency light passes through the frequency doubling enhancement module and the second beam splitter in sequence before outputting a high-power ultraviolet laser.

2. The high-power ultraviolet laser according to claim 1, characterized in that, The seed light module includes a 488nm semiconductor laser, a coupling lens group, a first total reflection mirror, a first Pr:YAP crystal, and an output mirror arranged in sequence; the optical surface of the first total reflection mirror is coated with a dielectric film that is highly transparent to the 488nm pump light and highly reflective to the 622nm fundamental frequency light; the first total reflection mirror and the output mirror constitute the seed local oscillator resonant cavity.

3. The high-power ultraviolet laser according to claim 1, characterized in that, The first beam splitter is a polarizing beam splitter; the beam combiner is a polarizing beam combiner.

4. The high-power ultraviolet laser according to claim 2, characterized in that, The first two-way amplification module includes a first polarizing beam splitter, a first pump module, a first quarter-wave plate and a third total reflection mirror arranged sequentially along the direction of light propagation; the first pump module includes a first pump LD bar pair; the operating wavelength of the first pump LD bar pair is 488nm; a second Pr:YAP crystal is disposed inside the first pump LD bar pair.

5. The high-power ultraviolet laser according to claim 4, characterized in that, The second double-pass amplification module has the same structure as the first double-pass amplification module, but the setting direction is opposite and the modules are staggered.

6. The high-power ultraviolet laser according to claim 5, characterized in that, The second two-way amplification module includes a second polarizing beam splitter, a second pump module, a second quarter-wave plate, and a fourth total reflection mirror arranged sequentially along the direction of light propagation; the second pump module includes a second pump LD bar pair; the operating wavelength of the second pump LD bar pair is 488nm; and a third Pr:YAP crystal is disposed inside the second pump LD bar pair.

7. The high-power ultraviolet laser according to claim 6, characterized in that, The fast axis / slow axis of the first and second quarter wave plates are at a 45° angle to the polarization direction of the incident light, which enables the incident linearly polarized light to become circularly polarized light after passing through once, and the polarization state to rotate 90° after passing through twice, thus realizing polarization state control and optical path isolation for double-pass amplification.

8. The high-power ultraviolet laser according to claim 7, characterized in that, The first, second, and third Pr:YAP crystals are all coated with an antireflective film that allows high transmission of 622nm fundamental frequency light on both ends.

9. The high-power ultraviolet laser according to claim 1, characterized in that, The frequency doubling enhancement module includes an enhancement cavity input mirror, a BBO crystal, and an enhancement cavity output mirror. The enhancement cavity input mirror and the enhancement cavity output mirror form a linear resonant cavity, and the BBO crystal is placed inside the resonant cavity. The enhancement cavity input mirror is coated with a dielectric film that is highly transparent to 622nm fundamental frequency light. The optical surface of the enhancement cavity output mirror is coated with a dielectric film that is highly reflective to 622nm fundamental frequency light and highly transparent to 311nm ultraviolet light. The two ends of the BBO crystal are coated with dual-band anti-reflection films for 622nm fundamental frequency light and 311nm ultraviolet light.

10. The high-power ultraviolet laser according to claim 1, characterized in that, The second beam splitter uses the difference in refractive index of light of different wavelengths to spatially separate the 622nm fundamental frequency light from the 311nm ultraviolet light.

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