Temperature-controlled high-energy-efficiency ultraviolet pulse laser

Abstract

This invention provides a temperature-controlled high-efficiency ultraviolet pulsed laser, belonging to the field of laser technology and thermal management. It comprises a semiconductor laser, a coupling lens group, a total reflection mirror, a praseodymium-doped yttrium aluminate crystal, a chromium-doped yttrium aluminate crystal, an output mirror, a first steering mirror, a second steering mirror, an intensifier cavity input mirror, a barium metaborate crystal, an intensifier cavity output mirror, and a third steering mirror, arranged sequentially along the optical transmission path. This invention solves the technical problem of low overall system energy efficiency and poor output power stability caused by the conflicting requirements of deep cryogenic cooling of the laser crystal and high-temperature annealing of the frequency doubling crystal, coupled with the limited cooling capacity of a single-stage TEC. It also solves the technical problem that existing independent temperature control methods cannot achieve multi-order-of-magnitude temperature difference control under limited power consumption, making it difficult to meet the stable operation requirements of high-power 311nm ultraviolet lasers in complex environments.

Description

Technical Field

[0001] This invention relates to the field of laser technology and thermal management, and in particular to a temperature-controlled high-efficiency ultraviolet pulsed laser. Background Technology

[0002] Deep ultraviolet pulsed lasers have extremely important applications in semiconductor detection, high-resolution laser spectroscopy, precision micromachining, and biomedicine. Among them, 311nm ultraviolet lasers have become a research hotspot in recent years due to their photothermal effects on specific biological tissues and their high signal-to-noise ratio in optical detection. Currently, one effective way to obtain 311nm lasers is by using praseodymium-doped lasers (Pr). 3+ A solid-state laser using praseodymium-doped yttrium aluminate (YA) generates a 622nm fundamental frequency beam, which is then subjected to second harmonic generation (SHG) via a nonlinear crystal. For the gain medium, yttrium aluminate (YAlO3, YAP), an orthorhombic oxide host, exhibits higher thermal conductivity (approximately 11 W·m⁻¹·K⁻¹) and superior mechanical hardness compared to traditional fluoride crystals (such as LiYF4), making it easier to achieve high beam quality output in high-power industrial environments. Furthermore, using a 488nm semiconductor laser or a frequency-doubled optically pumped semiconductor laser (2ω-OPSL) as the pump source is advantageous because its output wavelength is similar to that of praseodymium-doped yttrium aluminate crystals. 3 H4→ 3 The high matching of the P0 transition absorption peaks enables extremely high Stokes efficiency and reduces the internal thermal load of the crystal.

[0003] However, in actual operation, praseodymium-doped yttrium aluminate lasers in the 622nm band (corresponding to...) 3 P0→ 3 The conversion efficiency of the H6 transition is severely limited by the energy level thermal distribution. This is because the endpoint energy level of the 622nm transition is located within the ground state energy level group (…). 3 According to Boltzmann's distribution law, the Gaussian Stark level in yttrium praseodymium-doped ray crystal (Yttrium aluminate) exhibits a significant hot particle number distribution at room temperature (approximately 300 K), leading to substantial reabsorption losses during laser propagation within the crystal. Studies have shown that, without cooling measures, the stimulated emission cross-section of Yttrium aluminate doped with praseodymium at 622 nm is as high as 1.3 × 10⁻⁶. 19cm 2 However, its single-pass reabsorption loss can exceed 4%, which greatly increases the lasing threshold and suppresses the output power. Therefore, controlling the praseodymium-doped yttrium aluminate crystal in the deep cryogenic range to reduce the thermal distribution of the ground state energy level and thus suppress the reabsorption loss is a necessary means to improve the generation efficiency of 622nm fundamental frequency light.

[0004] Meanwhile, the subsequent frequency doubling process presents entirely opposite requirements for temperature management. In the process of converting 622nm laser light into 311nm ultraviolet laser light using barium borate (BBO) crystals, the high energy density of ultraviolet photons easily induces color centers within the BBO crystal. These color centers not only cause severe nonlinear absorption (NLA), leading to a significant decrease in ultraviolet output power over time, but also trigger a strong thermal lensing effect, damaging the transverse mode quality of the output beam. To alleviate this problem, current engineering practices typically employ thermal annealing, a dynamic repair technique. This involves heating the BBO crystal and maintaining it at a high temperature of approximately 180°C to increase the migration rate of defects within the crystal lattice and accelerate the annihilation of color centers. This mechanism is crucial for maintaining the long-term stability of high-power ultraviolet pulses.

[0005] In summary, high-performance 311nm ultraviolet laser systems face a severe temperature control dilemma: on the one hand, praseodymium-doped yttrium aluminate laser crystals require active cooling to suppress reabsorption; on the other hand, barium metaborate frequency-doubling crystals require active heating to suppress color center effects. Traditional laser designs typically employ two completely independent temperature control subsystems: a high-power thermoelectric cooler (TEC) cools the laser crystal and releases waste heat into the atmosphere, while a separate resistance heating wire heats the frequency-doubling crystal. This "heat dissipation on one side, heating on the other" operating mode not only leads to low overall system efficiency and redundant system size and weight, but also creates a severe temperature gradient field inside the laser, affecting the mechanical stability of the optical resonator. Balancing the internal heating and cooling requirements of the system, achieving efficient energy recycling, and optimizing the performance of each optical component has become a critical technical bottleneck in the field of high-stability ultraviolet pulsed lasers. Summary of the Invention

[0006] The purpose of this invention is to provide a temperature-controlled high-efficiency ultraviolet pulsed laser, which solves the technical problems of low overall system energy efficiency and poor output power stability caused by the contradiction between the deep cryogenic cooling requirements of laser crystals and the high-temperature annealing requirements of frequency doubling crystals, as well as the limited cooling capacity of single-stage TEC. It also solves the technical problems that existing independent temperature control methods cannot achieve cross-level temperature difference control under limited power consumption, and cannot meet the stable operation requirements of high-power 311nm ultraviolet lasers in complex environments.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A temperature-controlled high-efficiency ultraviolet pulsed laser includes a semiconductor laser, a coupling lens group, a total reflection mirror, a praseodymium-doped yttrium aluminate crystal, a chromium-doped yttrium aluminate crystal, an output mirror, a first steering mirror, a second steering mirror, an enhancement cavity input mirror, a barium borate crystal, an enhancement cavity output mirror, and a third steering mirror, arranged sequentially along the optical transmission path.

[0008] The sides of the praseodymium-doped yttrium aluminate crystal and the chromium-doped yttrium aluminate crystal are jointly wrapped with indium platinum and placed in the groove on the upper surface of the cold end heat sink. The praseodymium-doped yttrium aluminate crystal and the chromium-doped yttrium aluminate crystal are coupled to the cold end of the semiconductor refrigeration module through the cold end heat sink. The sides of the barium metaborate crystal are wrapped with indium platinum and wrapped with an electric heating wire. The barium metaborate crystal is placed in the groove on the lower surface of the hot end heat sink. The hot end of the semiconductor refrigeration module is thermally coupled to the barium metaborate crystal through the hot end heat sink and a directional heat conduction element. The waste heat discharged from the cold end of the semiconductor refrigeration module and the Joule heat of the component are used as the heat source for the high-temperature annealing of the barium metaborate crystal. The first sensor is in close contact with the surface of the praseodymium-doped yttrium aluminate crystal and is connected to the main controller. The main controller is connected to the second sensor and is in close contact with the surface of the barium metaborate crystal. A cooling fan is provided on the side of the hot end heat sink and is connected to the main controller.

[0009] Furthermore, the semiconductor laser is a 488nm semiconductor laser, adopting a quasi-continuous output mode, with an output center wavelength of 488nm, a spectral bandwidth of less than 3nm, a maximum output power of 20W, and the output beam spot diameter reduced to 2mm after coupling, with the divergence angle matching the absorption numerical aperture of the praseodymium-doped yttrium aluminate crystal.

[0010] Furthermore, the semiconductor cooling module is used to achieve directional energy transfer. The cold end of the semiconductor cooling module is used to construct a low-temperature gain region of -90℃ to -70℃ to suppress the ground-state reabsorption loss of the praseodymium-doped yttrium aluminate crystal. The waste heat recovered by the hot end of the semiconductor cooling module is directionally conducted to the barium metaborate crystal end through the hot end heat sink. Both the cold end heat sink and the hot end heat sink are copper heat sinks. When the recovered waste heat is insufficient to maintain the high-temperature annealing environment of 180℃, the main controller starts to perform thermal compensation, and the cooling fan turns on when the temperature of the hot end heat sink exceeds the safety threshold to dissipate excess heat.

[0011] Furthermore, both the first and second sensors are PT1000 high-precision platinum resistance temperature sensors. The main controller coordinates the drive current of the semiconductor refrigeration module and the compensation power of the electric heating wire based on the temperature signals fed back in real time from the first and second sensors. By utilizing the stepped temperature control logic of waste heat preheating and electric supplementary heating, the controller maintains the praseodymium-doped yttrium aluminate crystal and the chromium-doped yttrium aluminate crystal in a preset low-temperature range and the barium metaborate crystal in a preset high-temperature range.

[0012] Furthermore, the semiconductor refrigeration module is composed of multiple layers of refrigeration units stacked together, and the semiconductor refrigeration module provides an operating temperature difference of more than 80°C through the cascaded temperature difference superposition effect.

[0013] Furthermore, the barium metaborate crystal is disposed within an external enhancement cavity consisting of an enhancement cavity input mirror and an enhancement cavity output mirror, wherein the enhancement cavity input mirror serves as an incident coupling mirror.

[0014] Furthermore, the praseodymium-doped yttrium aluminate crystal is b-axis cut with a doping concentration of 1.0% and a size of 3mm×3mm×15mm. Both the incident and emitted light surfaces are coated with 488nm and 622nm antireflection films, respectively. The chromium-doped yttrium aluminate crystal is used as a saturable absorber for passive Q-switching compression.

[0015] Furthermore, the barium metaborate crystal adopts type I phase matching, has a size of 5mm×5mm×8mm, a cutting angle of θ=31.5°, φ=0°, and is coated with 622nm and 311nm dual-color antireflection films on both the incident and emitting surfaces.

[0016] Furthermore, the coupling lens group, total reflection mirror, output mirror, first steering mirror, second steering mirror, enhancement cavity input mirror, enhancement cavity output mirror and third steering mirror are all made of quartz, with a size of φ25.4mm and a thickness of 5mm.

[0017] Furthermore, the coupling lens group is anti-transmittive to 488nm pump light, the total reflection mirror is anti-transmittive to 488nm pump light and fully reflects 622nm fundamental frequency light, the output mirror partially transmits 622nm fundamental frequency light with a transmittance of 10%, the first and second steering mirrors fully reflect 622nm fundamental frequency light, the right surface of the enhancement cavity input mirror is anti-transmittive to the 622nm fundamental frequency light wavelength, and the left surface of the enhancement cavity input mirror is anti-transmittive to the 622nm fundamental frequency light wavelength and also reflects 311nm violet light. The external light is fully reflected. The left surface of the output mirror of the enhancement cavity is more transparent to 311nm ultraviolet light, and the right surface of the output mirror of the enhancement cavity is fully reflected to the 622nm fundamental frequency light wavelength and more transparent to 311nm ultraviolet light. The input mirror and the output mirror of the enhancement cavity together constitute the enhancement cavity to achieve high-efficiency conversion of the fundamental frequency light in the cavity to 311nm frequency-doubled light. The third steering mirror is highly reflective to 311nm ultraviolet light and highly transparent to 622nm fundamental frequency light to directionally emit high-purity 311nm ultraviolet laser.

[0018] Advantages of this invention: This invention achieves waste heat recovery and multi-source coordinated temperature control through a semiconductor refrigeration module. Compared to existing structures that utilize single-stage thermoelectric refrigeration with independent temperature control modules, this invention enables high-gain operation of praseodymium-doped yttrium aluminate crystals in a low-temperature range of -90℃ to -70℃. Furthermore, it can maintain the high-temperature annealing state of barium metaborate crystals by directional conduction of refrigeration waste heat, thereby improving the stability of ultraviolet laser output power. This invention features a compact structure, high energy efficiency, easy adjustment, and high reliability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention; In the diagram: 1. Semiconductor laser; 2. Coupled lens group; 3. Total reflection mirror; 4. Praseodymium-doped yttrium aluminate crystal; 5. Chromium-doped yttrium aluminate crystal; 6. Output mirror; 7. First steering mirror; 8. Second steering mirror; 9. Intensifier cavity input mirror; 10. Barium metaborate crystal; 11. Heating wire; 12. Intensifier cavity output mirror; 13. Third steering mirror; 14. Cold end heat sink; 15. Semiconductor cooling module; 16. Hot end heat sink; 17. First sensor; 18. Second sensor; 19. Cooling fan; 20. Main controller. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0021] like Figure 1 As shown, a temperature-controlled high-efficiency ultraviolet pulsed laser includes a semiconductor laser 1, a coupling lens group 2, a total reflection mirror 3, a praseodymium-doped yttrium aluminate crystal 4, a chromium-doped yttrium aluminate crystal 5, an output mirror 6, a first steering mirror 7, a second steering mirror 8, an enhancement cavity input mirror 9, a barium metaborate crystal 10, an enhancement cavity output mirror 12, and a third steering mirror 13 arranged sequentially along the optical transmission path.

[0022] The sides of the praseodymium-doped yttrium aluminate crystal 4 and the chromium-doped yttrium aluminate crystal 5 are both wrapped with indium platinum and placed in the groove on the upper surface of the cold end heat sink 14. The indium platinum wrapping ensures that both crystals can obtain normal heat dissipation and maintain stable operation. The praseodymium-doped yttrium aluminate crystal 4 and the chromium-doped yttrium aluminate crystal 5 are coupled to the cold end of the semiconductor refrigeration module 15 through the cold end heat sink 14. The barium metaborate crystal 10 is wrapped with indium platinum on its outer side and has an electric heating wire wrapped around it. The electric heating wire 11 is regulated by the main controller 20 for heat compensation when waste heat is insufficient, ensuring that the barium metaborate crystal 10 is maintained in a high-temperature annealed state of about 180°C.

[0023] The barium metaborate crystal 10 is placed in the groove on the lower surface of the hot end heat sink 16. The hot end of the semiconductor refrigeration module 15 is thermally coupled to the barium metaborate crystal 10 through the hot end heat sink 16 and the directional heat conduction element. The waste heat discharged from the cold end of the semiconductor refrigeration module 15 and the component Joule heat are used as the high-temperature annealing heat source for the barium metaborate crystal 10. The first sensor 17 is in close contact with the surface of the praseodymium-doped yttrium aluminate crystal 4. The first sensor 17 is connected to the main controller 20. The main controller 20 is connected to the second sensor 18. The second sensor 18 is in close contact with the surface of the barium metaborate crystal 10. A cooling fan 19 is provided on the side of the hot end heat sink 16. The cooling fan 19 is connected to the main controller 20.

[0024] In a preferred embodiment of the present invention, the semiconductor laser 1 is a 488nm semiconductor laser, which adopts a quasi-continuous output mode, with an output center wavelength of 488nm, a spectral bandwidth of less than 3nm, a maximum output power of 20W, and the beam spot diameter is reduced to 2mm after coupling. The divergence angle matches the absorption numerical aperture of the praseodymium-doped yttrium aluminate crystal 4.

[0025] In a preferred embodiment of the present invention, the semiconductor cooling module 15 is used to realize directional energy transfer. The cold end of the semiconductor cooling module 15 is used to construct a low-temperature gain region of -90℃ to -70℃ to suppress the ground state reabsorption loss of the praseodymium-doped yttrium aluminate crystal 4. The waste heat recovered by the hot end of the semiconductor cooling module 15 is directionally conducted to the barium metaborate crystal 10 through the hot end heat sink 16. Both the cold end heat sink 14 and the hot end heat sink 16 are copper heat sinks. When the recovered waste heat is insufficient to maintain the high-temperature annealing environment of 180℃, the main controller 20 starts to perform thermal compensation. The cooling fan 19 turns on when the temperature of the hot end heat sink 16 exceeds the safety threshold to dissipate excess heat.

[0026] In a preferred embodiment of the present invention, both the first sensor 17 and the second sensor 18 are PT1000 high-precision platinum resistance temperature sensors. The main controller 20 coordinates the driving current of the semiconductor refrigeration module 15 and the compensation power of the electric heating wire 11 based on the temperature signals fed back in real time by the first sensor 17 and the second sensor 18. By using the stepped temperature control logic of waste heat preheating and electric supplementary heating, the praseodymium-doped yttrium aluminate crystal 4 and chromium-doped yttrium aluminate crystal 5 are kept in a preset low temperature range, and the barium metaborate crystal 10 is kept in a preset high temperature range.

[0027] In a preferred embodiment of the present invention, the semiconductor cooling module 15 is composed of multiple layers of cooling units stacked together, and the semiconductor cooling module 15 provides an operating temperature difference of more than 80°C through the cascaded temperature difference superposition effect.

[0028] In a preferred embodiment of the present invention, the barium metaborate crystal 10 is disposed in an external enhancement cavity composed of an enhancement cavity input mirror 9 and an enhancement cavity output mirror 12, wherein the enhancement cavity input mirror 9 serves as an incident coupling mirror.

[0029] In a preferred embodiment of the present invention, the praseodymium-doped yttrium aluminate crystal 4 is b-axis cut with a doping concentration of 1.0% and a size of 3mm×3mm×15mm. Both the incident and emitting surfaces are coated with 488nm and 622nm antireflection films, respectively. The chromium-doped yttrium aluminate crystal 5 is used as a saturable absorber for passive Q-switching compression.

[0030] In a preferred embodiment of the present invention, the barium metaborate crystal 10 adopts type I phase matching, has a size of 5mm×5mm×8mm, a cutting angle of θ=31.5°, φ=0°, and is coated with 622nm and 311nm dual-color antireflection films on both the light-incident and light-exit surfaces.

[0031] In a preferred embodiment of the present invention, the coupling lens group 2, the total reflection mirror 3, the output mirror 6, the first steering mirror 7, the second steering mirror 8, the enhancement cavity input mirror 9, the enhancement cavity output mirror 12, and the third steering mirror 13 are all made of quartz, with a size of φ25.4mm and a thickness of 5mm.

[0032] In a preferred embodiment of the present invention, the coupling lens group 2 enhances the transmission of 488nm pump light, the total reflection mirror 3 enhances the transmission of 488nm pump light and fully reflects 622nm fundamental frequency light, the output mirror 6 partially transmits 622nm fundamental frequency light with a transmittance of 10%, the first steering mirror 7 and the second steering mirror 8 fully reflect 622nm fundamental frequency light, the right surface of the enhancement cavity input mirror 9 enhances the transmission of 622nm fundamental frequency light wavelength, and the left surface of the enhancement cavity input mirror 9 enhances the transmission of 622nm fundamental frequency light wavelength and 31nm fundamental frequency light wavelength. The system features a 1nm ultraviolet light total reflection capability. The left surface of the enhancement cavity output mirror 12 is made more transparent to 311nm ultraviolet light, while the right surface is made more transparent to 622nm fundamental frequency light and more transparent to 311nm ultraviolet light. The enhancement cavity input mirror 9 and the enhancement cavity output mirror 12 together form the enhancement cavity, which is used to achieve a high-efficiency conversion of the fundamental frequency light in the cavity to 311nm frequency-doubled light. The third steering mirror 13 is highly reflective to 311nm ultraviolet light and highly transparent to 622nm fundamental frequency light, which is used to directionally emit high-purity 311nm ultraviolet laser.

[0033] The working process of the laser of this invention: The 488nm pump light emitted by the semiconductor laser 1 is focused by the coupling lens group 2 and passes through the total reflection mirror 3 to enter the praseodymium-doped yttrium aluminate crystal 4. The cold end of the semiconductor cooling module 15 is closely attached to the praseodymium-doped yttrium aluminate crystal 4 and the chromium-doped yttrium aluminate crystal 5 through the cold end heat sink 14, using the low temperature environment to suppress the thermal particle number distribution of the gain medium and reduce reabsorption. Passive Q-switching compression is performed by the chromium-doped yttrium aluminate crystal 5 to generate a 622nm high peak power pulse. After being emitted by the output mirror 6, the beam is guided by the first steering mirror 7 and the second steering mirror 8 into the enhancement cavity composed of the enhancement cavity input mirror 9 and the enhancement cavity output mirror 12. The 622nm fundamental frequency light is cyclically enhanced in the cavity and excites the barium metaborate crystal 10 to generate 311nm ultraviolet light. The main controller 20 recovers the waste heat discharged from the heat sink 16 in real time and conducts it to the barium metaborate crystal 10. The barium metaborate crystal 10 is the frequency doubling end. The main controller 20, together with the electric heating wire 11, maintains the barium metaborate crystal 10 in the high-temperature range to suppress the color center effect. Finally, the 311nm ultraviolet laser is directed out by the third steering mirror 13.

[0034] Embodiments of the present invention: See Figure 1 A semiconductor laser 1 with an output center wavelength of 488nm and a power of 20W is used as the pump source, a praseodymium-doped yttrium aluminate crystal 4 is used as the gain medium, and a chromium-doped yttrium aluminate crystal 5 is used as the Q-switching medium to adjust the driving current of the semiconductor cooling module 15.

[0035] The effect on the output power of the 311nm ultraviolet laser was observed. As the cooling current increased, the peak power of the 622nm fundamental frequency pulse significantly increased when the temperature of the praseodymium-doped yttrium aluminate crystal 4 dropped to approximately -80℃. At this time, the waste heat discharged from the hot end of the semiconductor cooling module 15 was conducted to the barium metaborate crystal 10 via the hot end heat sink 16, and maintained at 180℃ by the electric heating wire 11. Through the resonant enhancement effect of the input mirror 9, the output conversion efficiency of the 311nm ultraviolet laser was improved by approximately 40%, and the power fluctuation rate was less than 3% during continuous operation for 4 hours.

[0036] Comparative experiments revealed that: If a traditional single-stage TEC is used, the laser crystal can only be cooled to about -30°C, resulting in large reabsorption loss of the fundamental frequency light, a significantly increased threshold, and limited power. If waste heat recovery is not implemented and the barium metaborate crystal 10 is not heated, the output power of the barium metaborate crystal 10 will drop by more than 30% after 15 minutes of operation due to the color center effect induced by the strong ultraviolet field of 311nm.

[0037] In summary, it can be seen that, through the synergistic effect of temperature control by the semiconductor cooling module 15, passive Q-switching, and frequency doubling of the enhancement cavity, a dynamic balance between the low-temperature gain of the laser crystal and the high-temperature annealing of the frequency doubling crystal is achieved, ultimately resulting in high-efficiency and long-term stable ultraviolet pulse output, and the overall power consumption is significantly better than that of the traditional dual independent temperature control system.

[0038] This invention employs an integrated thermal management structure, replacing the traditional single-stage cooler with a semiconductor cooling module 15 at the praseodymium-doped yttrium aluminate crystal 4. The superimposed temperature difference generated by the multi-stage cascade suppresses the laser crystal's operating temperature within the low-temperature gain region, physically inhibiting ground-state reabsorption loss. Simultaneously, this invention combines passive Q-switching technology with the chromium-doped yttrium aluminate crystal 5 with external enhancement cavity frequency doubling technology, and innovatively conducts waste heat discharged from the hot end of the cooling component to the barium metaborate crystal 10 via a hot-end heat sink 16 and directional heat-conducting elements. Through the coordinated scheduling of the current of the semiconductor cooling module 15 and the power of the auxiliary heating wire 11 by the main controller 20, energy utilization efficiency is improved, overcoming the shortcomings of traditional temperature control systems such as low energy efficiency and conflicting crystal temperature control requirements, ultimately achieving high-power and long-term stable 311nm ultraviolet laser output.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can still adjust the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Therefore, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A temperature-controlled high-efficiency ultraviolet pulsed laser, characterized in that: The system includes a semiconductor laser (1), a coupling lens group (2), a total reflection mirror (3), a praseodymium-doped yttrium aluminate crystal (4), a chromium-doped yttrium aluminate crystal (5), an output mirror (6), a first steering mirror (7), a second steering mirror (8), an enhancement cavity input mirror (9), a barium metaborate crystal (10), an enhancement cavity output mirror (12), and a third steering mirror (13), arranged sequentially along the optical transmission path. The sides of the praseodymium-doped yttrium aluminate crystal (4) and the chromium-doped yttrium aluminate crystal (5) are wrapped with indium platinum and placed in the groove on the upper surface of the cold end heat sink (14). The praseodymium-doped yttrium aluminate crystal (4) and the chromium-doped yttrium aluminate crystal (5) are coupled to the cold end of the semiconductor refrigeration module (15) through the cold end heat sink (14). The sides of the barium metaborate crystal (10) are wrapped with indium platinum and wrapped with an electric heating wire (11). The barium metaborate crystal (10) is placed in the groove on the lower surface of the hot end heat sink (16). The hot end of the semiconductor refrigeration module (15) is connected to the cold end of the semiconductor refrigeration module (15) through the hot end heat sink (16) and the directional heat conduction element. The barium metaborate crystal (10) is thermally coupled, and the waste heat discharged from the cold end of the semiconductor refrigeration module (15) and the component Joule heat are used as the high-temperature annealing heat source for the barium metaborate crystal (10). The first sensor (17) is in close contact with the surface of the praseodymium-doped yttrium aluminate crystal (4). The first sensor (17) is connected to the main controller (20). The main controller (20) is connected to the second sensor (18). The second sensor (18) is in close contact with the surface of the barium metaborate crystal (10). A cooling fan (19) is provided on the side of the hot end heat sink (16). The cooling fan (19) is connected to the main controller (20).

2. The temperature-controlled high-efficiency ultraviolet pulsed laser according to claim 1, characterized in that: The semiconductor laser (1) is a 488nm semiconductor laser, which adopts a quasi-continuous output mode, with an output center wavelength of 488nm, a spectral bandwidth of less than 3nm, a maximum output power of 20W, and a beam diameter reduced to 2mm after coupling. The divergence angle matches the absorption numerical aperture of the praseodymium-doped yttrium aluminate crystal (4).

3. A temperature-controlled high-efficiency ultraviolet pulsed laser according to claim 2, characterized in that: The semiconductor cooling module (15) is used to realize the directional transfer of energy. The cold end of the semiconductor cooling module (15) is used to construct a low temperature gain region of -90℃ to -70℃ to suppress the ground state reabsorption loss of the praseodymium-doped yttrium aluminate crystal (4). The waste heat recovered by the hot end of the semiconductor cooling module (15) is directionally conducted to the end of the barium metaborate crystal (10) through the hot end heat sink (16). Both the cold end heat sink (14) and the hot end heat sink (16) are copper heat sinks. When the recovered waste heat is insufficient to maintain the high temperature annealing environment of 180℃, the main controller (20) starts to perform thermal compensation. The cooling fan (19) turns on when the temperature of the hot end heat sink (16) exceeds the safety threshold to discharge excess heat.

4. A temperature-controlled high-efficiency ultraviolet pulsed laser according to claim 3, characterized in that: The first sensor (17) and the second sensor (18) are both PT1000 high-precision platinum resistance temperature sensors. The main controller (20) coordinates the driving current of the semiconductor refrigeration module (15) and the compensation power of the electric heating wire (11) according to the temperature signals fed back in real time by the first sensor (17) and the second sensor (18). It uses the stepped temperature control logic of waste heat preheating and electric supplementary heating to maintain the praseodymium-doped yttrium aluminate crystal (4) and chromium-doped yttrium aluminate crystal (5) in the preset low temperature range and the barium metaborate crystal (10) in the preset high temperature range.

5. A temperature-controlled high-efficiency ultraviolet pulsed laser according to claim 4, characterized in that: The semiconductor cooling module (15) is composed of multiple layers of cooling units stacked together. The semiconductor cooling module (15) provides a working temperature difference greater than 80°C through the cascaded temperature difference superposition effect.

6. A temperature-controlled high-efficiency ultraviolet pulsed laser according to claim 5, characterized in that: The barium metaborate crystal (10) is disposed in the external enhancement cavity formed by the enhancement cavity input mirror (9) and the enhancement cavity output mirror (12), wherein the enhancement cavity input mirror (9) serves as the incident coupling mirror.

7. A temperature-controlled high-efficiency ultraviolet pulsed laser according to claim 6, characterized in that: The praseodymium-doped yttrium aluminate crystal (4) is cut along the b-axis with a doping concentration of 1.0% and a size of 3mm×3mm×15mm. Both the incident and emitting surfaces are coated with 488nm and 622nm antireflection films, respectively. The chromium-doped yttrium aluminate crystal (5) is used as a saturated absorber for passive Q-switching compression.

8. A temperature-controlled high-efficiency ultraviolet pulsed laser according to claim 7, characterized in that: The barium metaborate crystal (10) adopts type I phase matching, with a size of 5mm×5mm×8mm, a cutting angle of θ=31.5°, φ=0°, and both the incident and exit surfaces are coated with 622nm and 311nm dual-color antireflection films.

9. A temperature-controlled high-efficiency ultraviolet pulsed laser according to claim 8, characterized in that: The coupling lens group (2), total reflection mirror (3), output mirror (6), first steering mirror (7), second steering mirror (8), enhancement cavity input mirror (9), enhancement cavity output mirror (12) and third steering mirror (13) are all made of quartz, with a size of φ25.4mm and a thickness of 5mm.

10. A temperature-controlled high-efficiency ultraviolet pulsed laser according to claim 9, characterized in that: The coupling lens group (2) is anti-transmitter for 488nm pump light, the total reflection mirror (3) is anti-transmitter for 488nm pump light and is fully reflective of 622nm fundamental frequency light, the output mirror (6) is partially transmittable of 622nm fundamental frequency light with a transmittance of 10%, the first steering mirror (7) and the second steering mirror (8) are fully reflective of 622nm fundamental frequency light, the right surface of the enhancement cavity input mirror (9) is anti-transmitter for 622nm fundamental frequency light wavelength, the left surface of the enhancement cavity input mirror (9) is anti-transmitter for 622nm fundamental frequency light wavelength and is also anti-transmitter for 311nm ultraviolet light. The light is totally reflected. The left surface of the enhancement cavity output mirror (12) is transparent to 311nm ultraviolet light, and the right surface of the enhancement cavity output mirror (12) is totally reflected to 622nm fundamental frequency light wavelength and transparent to 311nm ultraviolet light. The enhancement cavity input mirror (9) and the enhancement cavity output mirror (12) together constitute the enhancement cavity to achieve high-efficiency conversion of fundamental frequency light into 311nm frequency-doubled light in the cavity. The third steering mirror (13) is highly reflective to 311nm ultraviolet light and highly transparent to 622nm fundamental frequency light to directionally emit high-purity 311nm ultraviolet laser.

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