Ultra-low retroreflection laser power testing device

Abstract

The invention belongs to the field of laser testing, and provides an ultra-low retroreflection laser power testing device, which comprises a beam expanding system lens group; the beam expanding system lens group is configured to perform beam expanding on the high-power laser to be measured so as to reduce the laser power density; the wedge-shaped mirror is used for receiving the laser beam-expanded by the beam-expanding system mirror group and reflecting the laser with laser energy smaller than a preset value; the power meter receives the laser energy smaller than a preset value and calculates the laser power of the high-power laser to be measured based on the laser energy smaller than the preset value; the liquid medium attenuation absorber comprises a high-pressure sealing cavity and liquid arranged in the high-pressure sealing cavity, the wedge-shaped mirror serves as an incidence window and is arranged on one side of the high-pressure sealing cavity, and the liquid is configured to absorb laser energy transmitted by the wedge-shaped mirror. The stability, reliability and safety of the MOPA laser system in the testing process are improved, and accurate measurement of high-power CO2 laser in an EUV photoetching light source is achieved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of laser power detection, in particular to a laser power testing device with ultra-low back reflection. BACKGROUND

[0002] A photoetching machine is a core device for manufacturing large-scale integrated circuits-chips, and a photoetching light source is an important component of the photoetching machine. According to Rayleigh criterion, the shorter the wavelength of the light source is, the higher the photoetching resolution provided is, and an extreme ultra-violet photoetching (EUVL) with a wavelength of 13.5 nm is highly concerned. A laser produced plasma (LPP) can generate extreme ultra-violet light, and a mainstream technical approach is to irradiate a tin droplet target with a high-repetition, narrow-pulse-width and high-power CO2 laser to induce tin plasma to radiate 13.5 nm EUVL.

[0003] The high-repetition, narrow-pulse-width and high-power CO2 laser mainly adopts a Master Oscillator Power-Amplifier (MOPA) technical approach, that is, a high-repetition, narrow-pulse-width seed laser is power-amplified by a plurality of CO2 laser amplifiers to obtain high-power laser. Laser power and power stability are core performance parameters of the Master Oscillator Power-Amplifier (MOPA) system, and indexes thereof directly determine EUV light conversion efficiency and power, so that a high-power CO2 laser with a power of tens of kilowatts is required to be measured and characterized. Precise measurement and characterization of laser power are key technologies in research and application of the system.

[0004] Laser power measurement includes direct measurement and sampling indirect measurement. When a high-power CO2 laser is directly measured, since a power meter is not an absolute black body, backscattering laser is generated. The backscattering light of the tens-of-kilowatt CO2 laser is reversely amplified by a laser amplifier, and is enough to cause fatal damage to optical elements in a front end of the Master Oscillator Power-Amplifier (MOPA). A conventional sampling indirect measurement of a high-power CO2 laser usually adopts a sampling mirror with a known reflectivity, uses a power meter to receive reflected light, and calculates laser power, but high-power laser passing through the sampling mirror still needs to be absorbed by a solid-state energy absorber. Since the solid-state energy absorber is difficult to have both high diffuse reflectivity and high absorption, a high-absorption material finally has high back diffuse reflection, and after being reversely amplified by the laser amplifier, causes damage to the optical elements.

[0005] Therefore, a laser power testing device with ultra-low back reflection is provided to solve one of the above technical problems. SUMMARY

[0006] The purpose of this application is to provide a laser power testing device with ultra-low backreflection, which can solve at least one of the aforementioned technical problems. The specific solution is as follows: According to a specific embodiment of this application, a laser power testing device with ultra-low backreflection includes: A beam expander system mirror assembly; the beam expander system mirror assembly is configured to expand the beam of the high-power laser under test in order to reduce the laser power density; A wedge mirror receives the laser beam expanded by the beam expanding system's mirror group and reflects the laser beam with an energy less than a preset value; A power meter receives the laser energy that is less than a preset value and calculates the laser power of the high-power laser to be tested based on the laser energy that is less than the preset value. A liquid medium attenuation absorber includes a high-pressure sealed cavity and a liquid disposed within the high-pressure sealed cavity, wherein a wedge-shaped mirror is disposed on one side of the high-pressure sealed cavity as an incident window, and the liquid is configured to absorb laser energy transmitted through the wedge-shaped mirror.

[0007] In some embodiments, the beam expander system mirror group includes a primary mirror and a secondary mirror; the high-power laser to be tested passes through the Cassegrain structure composed of the secondary mirror and the primary mirror, and is reflected off-axis before being incident on the wedge mirror.

[0008] In some embodiments, the incident surface of the wedge mirror is coated with an antireflection film of ZnSe and air medium at a wavelength of 10.6 μm, with a reflectivity of <0.2%, and the exit surface is coated with an antireflection film of ZnSe and liquid medium at a wavelength of 10.6 μm, with a reflectivity of <0.2%.

[0009] In some embodiments, the inner side of the high-pressure sealing cavity is subjected to black anodizing treatment.

[0010] In some embodiments, the wavelength of the high-power laser to be tested is 10.6 μm, and the liquid is dimethyl silicone oil.

[0011] In some embodiments, the thickness H of the liquid within the high-pressure sealed cavity is determined according to the following relationship: ， in, I 0 represents the initial energy value of the laser. I Indicates the laser propagation distance L The energy value after that, α Indicates the attenuation coefficient of the liquid; Based on the energy value after propagation distance I Calculate the laser propagation distance based on the preset threshold. L， And ensure that the thickness H of the liquid inside the high-pressure sealed cavity is greater than the laser propagation distance. L。

[0012] In some embodiments, it also includes: A liquid cooling system is circulated in connection with the liquid medium attenuation absorber and is used to control the temperature and pressure of the liquid in the liquid medium attenuation absorber.

[0013] In some embodiments, the liquid cooling system includes: A pressure sensor is used to detect the pressure of the liquid inside the high-pressure sealed cavity; A pressure reducing valve is activated when the pressure reaches a preset threshold to reduce the pressure of the liquid in the high-pressure sealed cavity.

[0014] In some embodiments, it also includes: An explosion-proof valve is installed on one side of the liquid medium attenuation absorber. It is configured such that when the pressure reducing valve is opened, if the pressure value is still higher than the preset threshold, the explosion-proof valve opens to quickly reduce the pressure of the liquid in the high-pressure sealed cavity.

[0015] In some embodiments, the liquid cooling system includes: A temperature sensor is used to detect the temperature of the liquid inside the high-pressure sealed cavity, so as to control the temperature of the circulating liquid to remain stable within a preset range and avoid changes in the refractive index of the liquid caused by liquid vibration.

[0016] Compared with the prior art, the above-described solutions of this application have at least the following beneficial effects: The device provided in this application solves the problem of backlight damage to laser systems caused by diffuse reflection from energy absorbers and power meters, thus improving the stability, reliability, and safety of MOPA laser systems during testing. It also addresses the current limitations of solid-state energy absorbers and power meters in terms of low power handling capacity and susceptibility to damage, enabling precise measurement of high-power CO2 lasers in EUV lithography light sources. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 A schematic diagram of a laser power testing device with ultra-low back reflection provided in an embodiment of the present invention; Figure 2 A flowchart of a laser power testing method with ultra-low back reflection provided in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: In the diagram: 1. Secondary mirror, 2. Primary mirror, 3. Wedge mirror, 4. Liquid medium attenuation absorber, 5. Explosion-proof valve, 6. Liquid cooler, 7. Pressure reducing valve, 8. Temperature sensor, 9. Pressure sensor, 10. Power meter, 11. Dimethyl silicone oil, 12. Circulation pipeline. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the article or device that includes said element.

[0021] In existing high-power laser measurements, backscattered light damages optical components, causing the MOPA system to malfunction. This application proposes a novel method using a high-energy laser window and a liquid absorber. The window material is ZnSe crystal, coated with a 10.6μm wavelength antireflection film on both sides. The outer side of the liquid cavity has a high-transmittance film between air and the ZnSe medium, while the inner side has an antireflection film between the ZnSe medium and the liquid medium. The entrance window is a wedge-shaped mirror. When the high-power CO2 laser strikes the wedge-shaped mirror, reflected light deviates from the incident optical axis. By calibration and measuring the laser power of the reflected light, the incident CO2 laser power can be obtained. Since the measured light is low-power reflected light, it will not damage the power meter. The backscattered light power of the power meter is low, and upon re-passing through the wedge-shaped window mirror, it experiences a power attenuation of more than two orders of magnitude, thus preventing damage to the MOPA system's optical components. Simultaneously, the high-power laser entering the liquid medium attenuator is absorbed by the liquid. Since the diffuse reflectance is related to the purity of the liquid, using a high-purity liquid medium attenuator can significantly reduce the backscattered reflectance. The device described in this application can achieve ultra-low back reflectivity during high laser power measurement, solving the problem of backlight damaging optical components of the MOPA system.

[0022] The following is in conjunction with the appendix Figure 1 and 2 Detailed description of optional embodiments of the present invention.

[0023] According to a specific embodiment of the present invention, this application provides a laser power testing device with ultra-low backreflection, such as... Figure 1 As shown, it includes: A beam expander system mirror assembly; the beam expander system mirror assembly is configured to expand the beam of the high-power laser under test in order to reduce the laser power density; the beam expander system mirror assembly selects an appropriate beam expansion ratio according to the laser power. For example, the beam expander system mirror assembly uses a 4x beam expander system, which can expand the laser diameter by 4 times and reduce the laser power density by 16 times. The wedge mirror 3 receives the laser beam expanded by the beam expander system lens group and reflects the laser beam with a laser energy less than a preset value, for example, 0.2% energy reflection and 99.8% energy transmission; the angle of the wedge mirror 3 is designed to be 10° to avoid the reflected light back to the MOPA system; A power meter 10 receives the laser energy that is less than a preset value and calculates the laser power of the high-power laser to be measured based on the laser energy that is less than the preset value. For example, the laser power is calculated using 0.2% of the laser energy. The power meter 10 receives the laser reflected back from the first surface of the wedge mirror 3. Since the reflectivity of the wedge mirror 3 is known, the power of the incident laser can be calculated. Since the measured power is inherently low, even if the laser power is diffusely reflected and then reflected back to the amplifier by the wedge mirror 3, there will still be a power attenuation of more than two orders of magnitude, which will not interfere with the normal operation of the 10,000-watt MOPA system, thus achieving a dual balance between power measurement and optical path safety. The liquid medium attenuation absorber 4 includes a high-pressure sealed cavity and a liquid disposed within the high-pressure sealed cavity. The wedge-shaped mirror 3 is disposed on one side of the high-pressure sealed cavity as an incident window. The liquid is configured to absorb 99.8% of the energy of the laser transmitted through the wedge-shaped mirror 3. The high-pressure sealed cavity maintains the temperature and pressure of the liquid.

[0024] In some embodiments, the beam expander system includes a primary mirror 2 and a secondary mirror 1. The high-power laser to be measured passes through a Cassegrain structure composed of the secondary mirror 1 and the primary mirror 2, and after off-axis reflection, is incident on the wedge-shaped mirror 3. The secondary mirror 1 is a parabolic convex mirror, a copper-based liquid-cooled mirror with a reflectivity >99.5%@10.6μm. The primary mirror 2 of the beam expander system is a parabolic concave mirror, a copper-based liquid-cooled mirror with a reflectivity >99.5%@10.6μm. The Cassegrain structure, combined with off-axis reflection, achieves beam expansion without central obstruction, avoiding diffraction and beam quality degradation caused by traditional coaxial systems, and avoiding backscattered reflection and energy loss of the laser caused by obstruction by the primary mirror 2, thus improving the accuracy and safety of high-power laser measurement.

[0025] In some embodiments, the wedge mirror 3 is coated with an antireflection film of ZnSe and air medium at a wavelength of 10.6 μm on the incident side and with an antireflection film of ZnSe and liquid medium at a wavelength of 10.6 μm on the exit side, ensuring high transmittance at a wavelength of 10.6 μm.

[0026] In some embodiments, the inner side of the high-pressure sealing cavity is treated with black anodizing; for example, the high-pressure sealing cavity is made of 316 stainless steel, with a length, width and height of 30cm*30cm*30cm. The black surface improves the absorption capacity of leaked laser light, prevents stray light caused by cavity wall reflection, and reduces the safety risks of residual reflected light to operators and equipment.

[0027] In some embodiments, the wavelength of the high-power laser to be tested is 10.6 μm, and the liquid is dimethyl silicone oil 11. Diffuse reflectivity is related to the purity of the liquid; using a high-purity liquid medium attenuator can significantly reduce backscattered reflectivity, avoid laser-induced breakdown or chemical reactions, and ensure long-term stable operation. In some embodiments, the thickness H of the liquid inside the high-pressure sealed cavity is determined according to the following relationship: ， in, I 0 represents the initial energy value of the laser. I Indicates the laser propagation distance L The energy value after that, α This represents the attenuation coefficient of the liquid. It is determined by the energy value after propagation distance. I Calculate the laser propagation distance based on the preset threshold. L， And ensure that the thickness H of the liquid inside the high-pressure sealed cavity is greater than the laser propagation distance. L。 For example, dimethyl silicone oil 11 absorbs The laser power, and the absorption coefficient of dimethyl silicone oil for a 10.6μm laser is approximately 1 cm⁻¹. -1 The absorption of this laser is nearly three orders of magnitude weaker than that of commonly used liquid pure water, which can significantly increase the transmission distance of the laser and avoid the boiling phenomenon caused by the rapid absorption of laser light by the liquid. For CO2 lasers with an intensity of tens of kilowatts, when the residual light intensity after liquid absorption is in the tens of watts range, the backscattered light will not have a significant impact on the laser system, i.e., I / I 0.1%, assuming I is the preset threshold, will not damage the high-pressure sealing cavity. Using the above formula, the propagation distance L through the 11 layers of dimethyl silicone oil is approximately 7cm. Therefore, the thickness H of the liquid inside the high-pressure sealing cavity only needs to be greater than 10cm. This can also be understood by using the initial laser energy value. I 0, laser propagation distance L The energy value after IThe thickness H of the liquid inside the high-pressure sealed cavity was calculated and will not be elaborated here. Dimethyl silicone oil 11 can efficiently capture laser energy transmitted to the cavity through the optical path, and its own temperature rises synchronously with the continuous accumulation of energy, with the heat being carried away by the liquid circulation system. At the same time, dimethyl silicone oil 11 has advantages such as low high temperature resistance, non-vaporization, strong chemical inertness, stable physical properties, non-corrosiveness, and maintenance-free characteristics. It not only ensures the directional absorption and uniform conduction of laser energy, but also avoids the corrosion of the cavity by the working fluid and the scattering interference of the laser, providing a stable working fluid basis for the subsequent heat exchange process.

[0028] In some embodiments, the ultra-low backreflection laser power testing device further includes a liquid cooling system, comprising a liquid cooler 6 and a circulation pipe 12. The liquid cooling system is circulatedly connected to the liquid medium attenuation absorber 4 and is used to control the temperature and pressure of the liquid in the liquid medium attenuation absorber 4. The high-pressure sealing cavity has an inlet and an outlet, forming a circulation loop through the circulation pipe 12 and the liquid cooler 6. The liquid flow in the circulation pipe 12 carries away the heat in the high-pressure sealing cavity, providing a continuous and stable cooling liquid for the liquid medium attenuation absorber and maintaining the temperature stability of the liquid medium attenuation absorber. Dimethyl silicone oil 11 absorbs laser energy, passes through the circulation pipe 12, is transported to the external liquid cooler 6 for cooling, and then returns to the liquid medium attenuation absorber, ensuring long-term stable operation. The circulation pipe 12 guides the heated dimethyl silicone oil 11 to the external liquid cooler 6, allowing the dimethyl silicone oil 11 to exchange heat with the heat dissipation system of the liquid cooler 6. After its temperature drops to the preset working range, the circulation pipe 12 returns the cooled dimethyl silicone oil 11 to the high-pressure sealed chamber of the liquid medium attenuation absorber, enabling the dimethyl silicone oil 11 to repeatedly participate in the laser energy absorption process. The circulation pipe 12 has sealing, temperature resistance, and low flow resistance characteristics, which can ensure the continuity of dimethyl silicone oil 11 circulation and heat exchange efficiency, thereby maintaining the thermal management stability of the liquid medium attenuation absorber and enabling it to withstand continuous lasers at the kilowatt level. During operation, it adapts to the changes in the heat load of the liquid medium attenuation absorber in real time, efficiently removing the heat generated when the laser irradiates the liquid medium through the circulating dimethyl silicone oil 11, and precisely controlling the liquid temperature to remain stable within the preset range, avoiding changes in refractive index caused by fluctuations in the dimethyl silicone oil 11.

[0029] In some embodiments, the liquid cooling system further includes: Pressure sensor 9 is used to detect the pressure of the liquid inside the high-pressure sealed cavity; Pressure reducing valve 7 opens when the pressure reaches a preset threshold to reduce the pressure of the liquid in the high-pressure sealing chamber; The real-time data from pressure sensor 9 provides core signal support for pressure control, accurately captures pressure fluctuations, provides triggering basis for the start and stop adjustment of pressure reducing valve 7, avoids safety accidents, and adjusts system parameters according to pressure data to maintain the optimal working state of the liquid medium decay absorber.

[0030] In some embodiments, the laser power testing device further includes an explosion-proof valve 5, disposed on one side of the liquid medium attenuation absorber 4. The valve is configured such that when the pressure reducing valve 7 is opened, and the pressure value remains higher than the preset threshold, the explosion-proof valve 5 automatically opens to rapidly reduce the pressure of the liquid within the high-pressure sealed cavity, preventing the high-pressure sealed cavity from exploding. As a passive emergency pressure relief component, the explosion-proof valve 5 is set with a burst threshold higher than the upper limit of the pressure reducing valve 7. It only opens and releases pressure when the pressure within the high-pressure sealed cavity exceeds the adjustment capacity of the pressure reducing valve 7 and reaches a dangerous critical value, protecting the testing device. As an active pressure stabilizing component, the pressure reducing valve 7 is preset with a safe pressure threshold within the cavity. When the pressure sensor 9 detects that the pressure within the cavity is close to the upper limit of the threshold, the pressure reducing valve 7 automatically opens in overflow pressure relief mode, stabilizing the pressure within a safe range through gradient pressure relief, avoiding accidental triggering of the emergency explosion-proof mechanism due to frequent pressure fluctuations.

[0031] In some embodiments, the liquid cooling system further includes: Temperature sensor 8 is used to detect the temperature of the liquid inside the high-pressure sealed cavity to control the circulating liquid temperature to remain stable within a preset range, avoiding changes in the liquid's refractive index caused by liquid fluctuations. Temperature sensor 8 collects real-time temperature data of the circulating dimethyl silicone oil 11 and the inner wall of the cavity, and is linked to pressure sensor 9. Overheating triggers enhanced heat dissipation or laser shutdown to block thermally induced pressure increases. Simultaneously, it monitors the temperature of dimethyl silicone oil 11 in real time to prevent overheating that could lead to vaporization or decreased absorption efficiency. Temperature monitoring contributes to the accuracy of power measurement.

[0032] According to a specific embodiment of this application, this application further provides a method for testing laser power with ultra-low backreflection, such as... Figure 2 As shown, the method includes the following steps: S1: The primary mirror 2 and secondary mirror 1 expand the laser beam to reduce the power density of the high-power laser under test; S2: The wedge mirror 3 reflects a preset value of laser energy, such as 0.2%, to the power meter 10, which is configured to detect the power of the laser; the transmitted laser energy, such as 99.8%, is absorbed by dimethyl silicone oil 11 in the liquid medium attenuation absorber.

[0033] Due to the 10,000 watt level The laser has extremely high energy density, and when it irradiates dimethyl silicone oil 11, it will instantly form a local high-temperature zone. Therefore, the liquid medium attenuation absorber is designed with high pressure sealing and has built-in high-precision temperature sensor 8 and pressure sensor 9 to collect the temperature and pressure parameters in the cavity in real time. When the temperature of dimethyl silicone oil 11 is detected to be close to the preset threshold, the system will trigger the dynamic adjustment of the cooling power of the water cooling system. If the pressure exceeds the safe range, the active pressure stabilization process will be activated simultaneously to control the pressure reducing valve 7 to release pressure in a gradient manner to maintain the stability of the pressure in the cavity. At the same time, the device is equipped with an explosion-proof valve 5 as a passive safety redundancy. Once the pressure exceeds the adjustment limit of the pressure reducing valve 7, the explosion-proof valve 5 will respond quickly to complete the emergency pressure relief to avoid structural damage to the device due to overpressure.

[0034] This method fundamentally reduces the risk of back reflection by controlling the energy distribution ratio. By combining low-ratio sampling (0.2%) with high-ratio absorption (99.8%), non-destructive measurement is achieved. It is applicable to lasers of different power levels and only requires adjustment of the beam expansion ratio, reflectivity, and liquid flow rate or type. It can be seamlessly integrated with existing MOPA systems without interfering with the normal optical path, and provides non-destructive testing of laser power in MOPA systems.

[0035] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0036] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A laser power testing device with ultra-low backreflection, characterized in that, include: A beam expander system mirror assembly; the beam expander system mirror assembly is configured to expand the beam of the high-power laser under test in order to reduce the laser power density; A wedge mirror receives the laser beam expanded by the beam expanding system's mirror group and reflects the laser beam with an energy less than a preset value; A power meter receives the laser energy that is less than a preset value and calculates the laser power of the high-power laser to be tested based on the laser energy that is less than the preset value. A liquid medium attenuation absorber includes a high-pressure sealed cavity and a liquid disposed within the high-pressure sealed cavity, wherein a wedge-shaped mirror is disposed on one side of the high-pressure sealed cavity as an incident window, and the liquid is configured to absorb laser energy transmitted through the wedge-shaped mirror.

2. The apparatus according to claim 1, characterized in that, The beam expander system includes a primary mirror and a secondary mirror; the high-power laser to be tested passes through the Cassegrain structure composed of the secondary mirror and the primary mirror, and is reflected off-axis before being incident on the wedge mirror.

3. The apparatus according to claim 1, characterized in that, The incident surface of the wedge mirror is coated with an antireflection film of ZnSe and air medium at a wavelength of 10.6 μm, with a reflectivity of <0.2%. The exit surface is coated with an antireflection film of ZnSe and liquid medium at a wavelength of 10.6 μm, with a reflectivity of <0.2%.

4. The apparatus according to claim 1, characterized in that, The inner side of the high-pressure sealing cavity is treated with black anodizing.

5. The apparatus according to claim 1, characterized in that, The wavelength of the high-power laser to be tested is 10.6 μm, and the liquid is dimethyl silicone oil.

6. The apparatus according to claim 5, characterized in that, The thickness H of the liquid inside the high-pressure sealed cavity is determined according to the following relationship: ， in, I 0 represents the initial energy value of the laser. I Indicates the laser propagation distance L The energy value after that, α Indicates the attenuation coefficient of the liquid; Based on the energy value after propagation distance I Calculate the laser propagation distance based on the preset threshold. L， And ensure that the thickness H of the liquid inside the high-pressure sealed cavity is greater than the laser propagation distance. L。 7. The apparatus according to claim 1, characterized in that, Also includes: A liquid cooling system is circulated in connection with the liquid medium attenuation absorber and is used to control the temperature and pressure of the liquid in the liquid medium attenuation absorber.

8. The apparatus according to claim 7, characterized in that, The liquid cooling system includes: A pressure sensor is used to detect the pressure of the liquid inside the high-pressure sealed cavity; A pressure reducing valve is activated when the pressure reaches a preset threshold to reduce the pressure of the liquid in the high-pressure sealed cavity.

9. The apparatus according to claim 8, characterized in that, Also includes: An explosion-proof valve is installed on one side of the liquid medium attenuation absorber. It is configured such that when the pressure reducing valve is opened, if the pressure value is still higher than the preset threshold, the explosion-proof valve opens to quickly reduce the pressure of the liquid in the high-pressure sealed cavity.

10. The apparatus according to claim 7, characterized in that, The liquid cooling system includes: A temperature sensor is used to detect the temperature of the liquid inside the high-pressure sealed cavity, so as to control the temperature of the circulating liquid to remain stable within a preset range and avoid changes in the refractive index of the liquid caused by liquid vibration.

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