A deep ultraviolet solid-state laser based on NH4B4O6F crystal

Abstract

This invention provides a deep ultraviolet solid-state laser based on NH4B4O6F crystal. The laser comprises an ultraviolet laser, a frequency doubling device, a beam-splitting prism, a beam shaping system, a vacuum cavity, an entrance window, an exit window, and a beam terminator. Several frequency converters convert near-infrared laser light into 318-410nm ultraviolet laser light. The beam shaping system shapes the ultraviolet laser light into a spatial beam profile conducive to improving frequency doubling output. The ultraviolet laser light is then incident on the frequency doubling device located inside the vacuum cavity system, directly frequency doubling to output 159-205nm deep ultraviolet laser light. This laser has advantages such as system simplicity, convenient operation, stable laser output, compact size, and low cost, and can be applied in cutting-edge scientific research equipment, precision machining, optical detection, and other fields.

Description

Technical Field

[0001] This invention relates to the field of solid-state laser technology, and mainly to a deep ultraviolet solid-state laser based on NH4B4O6F crystal, which can realize a solid-state deep ultraviolet laser with a wavelength of 159-205nm through direct frequency doubling. Background Technology

[0002] Deep ultraviolet (<200nm) lasers, with their advantages of high single-photon energy, short optical period, and high spatial resolution, are widely used in cutting-edge scientific fields such as atomic clock cooling, precision machining, photolithography, and photoelectron spectroscopy, and have significant application value. Currently, the most effective way to achieve high-quality deep ultraviolet laser output is through deep ultraviolet solid-state laser technology based on nonlinear frequency up-conversion. This technology combines the advantages of solid-state lasers—high beam quality, small size, and high frequency doubling efficiency of nonlinear optical crystals—and has become a major trend in laser technology research. In the field of precision machining, compared with commonly used large-volume, high-cost gas-medium ultraviolet excimer lasers, solid-state lasers have been widely used due to their reasonable price, high throughput, and small size.

[0003] The core of deep-ultraviolet (DUV) solid-state laser technology is the nonlinear optical crystal used for frequency conversion. Nonlinear optical crystals in the DUV band must meet the basic requirements of transparency in the DUV band, phase matching capability, and sufficient nonlinear optical coefficients. Currently, the only crystal that can meet these requirements and achieve practical applications for direct frequency doubling to realize DUV all-solid-state laser technology is the KBe2BO3F2 (KBBF) family crystal. However, it has a severe layered growth habit, which brings difficulties to crystal growth and processing, and DUV laser output can only be achieved through prism coupling technology, which is not conducive to industrialization. In general, there are very few materials that can meet the requirements of DUV nonlinear optical materials, making it difficult to further advance the development of DUV lasers.

[0004] The Xinjiang Institute of Physics and Chemistry, Chinese Academy of Sciences, has made the world's first discovery of the NH4B4O6F crystal (Guoqiang Shi, Ying Wang, Fangfang Zhang, Bingbing Zhang, Zhihua Yang, Xueling Hou, Shilie Pan, Kenneth R. Poeppelmeie, "Finding the Next Deep-Ultraviolet NonlinearOptical Material: NH4B4O6F", Journal of the American Chemical Society, 2017(139): 10645). They have developed several technologies, including nonlinear optical crystal growth equipment and crystal growth techniques. This crystal material does not contain highly toxic beryllium oxide, exhibits no layered growth habit, has a band gap of 7.95 eV, a deep ultraviolet transparency range as short as 156 nm, a minimum phase-matching wavelength of 158 nm, and a nonlinear optical coefficient d. 11 =1pm / V, which meets all the requirements of deep ultraviolet nonlinear optical crystals.

[0005] In summary, NH4B4O6F crystals can achieve direct frequency doubling output in the 159-205nm deep ultraviolet range, enabling high-power, high-efficiency, compact integration, and small-sized laser devices, which are conducive to industrialization. Summary of the Invention

[0006] The purpose of this invention is to address the difficulty in achieving 159-205nm solid-state deep ultraviolet lasers by proposing a deep ultraviolet solid-state laser based on NH4B4O6F crystal. This laser comprises an ultraviolet laser, a frequency doubling device, a beam-splitting prism, a beam shaping system, a vacuum cavity, an entrance window, an exit window, and a beam terminator. Several frequency converters convert near-infrared laser light into 318-410nm ultraviolet laser light. The beam shaping system shapes the ultraviolet laser light into a spatial beam profile conducive to improving frequency doubling output. The ultraviolet laser light is then incident on the frequency doubling device located inside the vacuum cavity system, directly frequency doubling to output 159-205nm deep ultraviolet laser light. This laser has advantages such as system simplicity, ease of operation, stable laser output, compact size, and low cost, and can be applied in cutting-edge scientific research equipment, precision machining, optical detection, and other fields.

[0007] The present invention discloses a deep ultraviolet solid-state laser based on NH4B4O6F crystal. The laser consists of an ultraviolet laser (1), a frequency doubling device (2), a beam splitter prism (3), a beam shaping system (4), a vacuum cavity (5), an entrance window (6), an exit window (7), and a beam terminator (8). The ultraviolet laser (1) is connected in series with the frequency doubling device (2) through the beam shaping system (4), the vacuum cavity (5), and the entrance window (6). The frequency doubling device (2) is connected to the beam splitter prism (3). The beam splitter prism (3) is connected to the exit window (7) and the beam terminator (8) respectively. The specific operation is carried out according to the following steps: a. The ultraviolet laser (1) emits ultraviolet laser. After passing through the beam shaping system (4), the spatial intensity distribution of the beam is matched with the frequency doubling device (2). It enters the vacuum cavity (5) of nitrogen or inert gas environment through the incident window (6) and passes through the frequency doubling device (2). b. The frequency doubling device (2) is placed in the light transmission direction with the phase matching angle. The frequency doubling device (2) generates deep ultraviolet frequency doubling laser. Due to dispersion, the remaining ultraviolet fundamental frequency light passing through the frequency doubling device (2) and the output deep ultraviolet frequency doubling light pass through the beam splitting prism (3) placed with the Brewster angle of the deep ultraviolet frequency doubling light. The ultraviolet fundamental frequency beam and the deep ultraviolet frequency doubling beam are separated by a deflection angle of 5-30°. c. The remaining ultraviolet fundamental frequency laser is collected by the beam terminator (8), and the deep ultraviolet laser is emitted through the emission window (7) set in the transmission direction.

[0008] The ultraviolet laser (1) includes a first ultraviolet laser consisting of a Ti:sapphire laser (9), a first frequency converter (10) and a first beam splitter (11); Or a second ultraviolet laser consisting of a neodymium-doped yttrium aluminum garnet laser (17), a second frequency converter (18), a third frequency converter (19), and a second beam splitter (20); Alternatively, a third ultraviolet laser may be composed of a 1064nm high-reflectivity mirror (29), a neodymium-doped yttrium vanadate laser crystal (30), a potassium dihydrogen phosphate electro-optic Q-switching crystal (31), a 1064nm partial reflector (32), a fourth frequency converter (33), a third beam splitter (34), a 640-820nm high-reflectivity lens (36), a lithium triborate crystal (37), a 640-820nm partial reflector lens (38), a fourth beam splitter (39), and a sixth frequency converter (41).

[0009] The ultraviolet laser (1) consists of an infrared fundamental frequency light source and several frequency converters; the infrared fundamental frequency light source is a 640-950nm Ti:sapphire laser, a 1030nm-1080nm ytterbium laser, a 1064nm or 1.3μm neodymium laser, which generates and outputs an ultraviolet laser with a wavelength of 318-410nm through one or more frequency converters that perform frequency doubling, summing, optical parameter generation, optical parameter amplification, optical parameter oscillation and difference frequency.

[0010] The frequency doubling device (2) includes a first frequency doubling device (14), a second frequency doubling device (24), and a third frequency doubling device (44). The frequency doubling device (2) is made of NH4B4O6F crystal, which can directly double the frequency to achieve 159-205nm deep ultraviolet output. The light transmission direction of the frequency doubling device (2) is the phase matching direction of the ultraviolet laser frequency doubling to 159-205nm deep ultraviolet laser. The incident surface of the frequency doubling device (2) is processed to be normal incident or Brewster angle incident of ultraviolet pump light, and the exit surface is processed to be parallel to the incident surface or Brewster angle exit of deep ultraviolet frequency doubling light. The phase matching cutting angle of the 159-205nm deep ultraviolet laser output is 50°-90°.

[0011] The beam splitter (3) includes a first beam splitter (15), a second beam splitter (26) and a third beam splitter (46); the beam splitter (3) is composed of a material with high transmittance in the deep ultraviolet band, the laser incident surface and the exit surface are in the Brewster angle direction of the output deep ultraviolet laser, and both sides are polished; the material of the beam splitter (3) is silicon dioxide or calcium fluoride, and the apex angle used for beam splitting is 56.1-59.6°.

[0012] The beam shaping system (4) includes a first beam shaping system (13), a second beam shaping system (22) and a third beam shaping system (42); the beam shaping system (4) is composed of spherical, cylindrical, aspherical lenses, spherical, cylindrical, aspherical mirrors or super-Gaussian shaping lenses, and is used to shape the spatial profile of the ultraviolet laser beam.

[0013] The vacuum cavity (5) includes a first vacuum cavity (25) and a second vacuum cavity (45). The vacuum cavity (5) consists of a sealed cavity, a cavity light transmission window, and a vacuum pump. The sealed cavity is evacuated or filled with nitrogen or inert gas to ensure that the frequency doubling device (2) outputs deep ultraviolet laser in a vacuum or nitrogen / inert gas environment. The light transmission window of the vacuum cavity (5) is made of a material with high transmittance to ultraviolet laser and deep ultraviolet frequency doubling laser. The ultraviolet laser emitted by the ultraviolet laser (1) enters the vacuum cavity (5) through the light transmission window at one end of the sealed cavity. It enters the frequency doubling device (2) by normal incidence or Brewster angle incidence, generating and outputting 159-205nm deep ultraviolet laser, which is output from the exit window on the vacuum cavity (5) set in its propagation direction.

[0014] The incident window (6) includes a first incident window (23) and a second incident window (43); the exit window (7) includes a first exit window (27) and a second exit window (47); the beam terminator (8) includes a first beam terminator (12), a second beam terminator (16), a third beam terminator (21), a fourth beam terminator (28), a fifth beam terminator (35), a sixth beam terminator (40), and a seventh beam terminator (48).

[0015] The frequency doubling device (2) is made of NH4B4O6F crystal, processed according to the phase matching angle direction of the output laser, and the light-transmitting surface is polished.

[0016] This invention discloses a deep ultraviolet solid-state laser based on NH4B4O6F crystal. The laser comprises an ultraviolet laser (1), a frequency doubling device (2), a beam splitter prism (3), and a beam shaping system (4). The 159-190nm wavelength range suffers severe energy loss in air, requiring a vacuum cavity system (5). The ultraviolet laser achieves a wavelength range of 318-410nm using a nonlinear frequency conversion method with a 640-950nm Ti:sapphire laser, a 1030nm-1080nm ytterbium laser, a 1064nm or 1.3μm neodymium laser. The wavelength of the ultraviolet laser; the frequency doubling device (2) is made of NH4B4O6F crystal that can directly double the frequency to achieve 159-205nm deep ultraviolet output. The light transmission direction of the frequency doubling device (2) is the phase matching direction of the ultraviolet laser frequency doubling to 159-205nm deep ultraviolet laser. The incident surface of the frequency doubling device (2) is processed to be normal incident or Brewster angle incident of ultraviolet pump light, and the exit surface is processed to be parallel to the incident surface or Brewster angle exit of deep ultraviolet frequency-doubled light; the beam shaping system (4) consists of spherical, cylindrical, aspherical lenses, and spherical... The system consists of a surface, cylindrical, aspherical, or super-Gaussian shaping lens for shaping the spatial profile of the ultraviolet laser beam; the beam splitter prism (3) is made of a high-transmittance material in the deep ultraviolet band, with the laser incident surface and exit surface aligned with the Brewster angle of the output deep ultraviolet laser, and both surfaces are polished to separate the ultraviolet laser and the deep ultraviolet laser; the vacuum cavity system (5) consists of a sealed cavity, a cavity light-transmitting window, and a vacuum pump, with the sealed cavity evacuated or filled with nitrogen or inert gas to ensure that the frequency doubling device (2) operates in a vacuum or in nitrogen or inert gas environment. The cavity generates a frequency-doubled deep ultraviolet laser within the environment to prevent the frequency-doubled deep ultraviolet laser from being absorbed and lost by oxygen or water vapor. The cavity's light transmission window is made of a material with high transmittance to the ultraviolet pump laser and the deep ultraviolet frequency-doubled laser. The ultraviolet laser emitted by the ultraviolet laser enters the cavity through the light transmission window at one end of the sealed cavity and enters the frequency doubling device (2) by normal incidence or Brewster angle incidence, generating and outputting a 159-205nm deep ultraviolet laser. The ultraviolet pump light is collected by the beam cutoff device, and the deep ultraviolet laser is output from the exit window set in its propagation direction.

[0017] The ultraviolet laser consists of a fundamental frequency laser and 1-3 frequency converters; the fundamental frequency light source consists of an excitation device composed of a high-reflection mirror for the fundamental frequency laser, a partial-reflection mirror for the fundamental frequency laser, and a laser gain medium, wherein the laser gain medium is a titanium sapphire crystal, a crystal doped with neodymium or ytterbium, glass, ceramic, or optical fiber material; the frequency converters mainly include a frequency multiplier generator, a sum frequency generator, an optical parametric generator, an optical parametric amplifier, an optical parametric oscillator, and a difference frequency generator.

[0018] The frequency doubling device (2) is an NH4B4O6F crystal, also known as ammonium fluoroborate crystal, with the chemical formula NH4B4O6F and a molecular weight of 176.28. It belongs to the orthorhombic crystal system and has a space group of [missing information]. Pna 21, with unit cell parameters a = 7.602(2) Å, b = 11.197(3) Å, c = 6.5952(19) Å, α = 90°, β = 90°, γ = 90°.

[0019] The NH4B4O6F crystal outputs a 159-205nm deep ultraviolet laser with a phase-matched cutting angle of 50°-90°.

[0020] The beam-splitting prism is made of silicon dioxide or calcium fluoride, and the apex angle for beam splitting is 56.1-59.6°. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the 159-205nm solid-state deep ultraviolet laser output by direct frequency doubling of NH4B4O6F deep ultraviolet laser of the present invention. Figure 2 This is a schematic diagram of the 193nm wavelength tunable solid-state deep ultraviolet laser with direct frequency doubling output from NH4B4O6F in Example 2. Figure 3 This is a schematic diagram of the 177.3nm solid-state deep ultraviolet laser output from NH4B4O6F deep ultraviolet direct frequency doubling in Example 3; Figure 4 This is a schematic diagram of the structure of the 159-205nm wavelength tunable solid-state deep ultraviolet laser with direct frequency doubling output from NH4B4O6F in Example 4. Detailed Implementation

[0022] The present invention will be further described below with reference to embodiments. It should be noted that the given embodiments are not intended to limit the scope of protection of the present invention, and any improvements made based on the present invention do not depart from the spirit of the present invention. Unless otherwise specified, all components or devices used in the present invention are commercially available. Example 1

[0023] Figure 1This is a schematic diagram of the device of the present invention: The deep ultraviolet solid-state laser based on NH4B4O6F crystal described in this invention consists of an ultraviolet laser 1, a frequency doubling device 2, a beam splitter prism 3, a beam shaping system 4, a vacuum cavity 5, an entrance window 6, an exit window 7, and a beam terminator 8. The ultraviolet laser 1 is connected in series with the frequency doubling device 2 through the beam shaping system 4, the vacuum cavity 5, and the entrance window 6. The frequency doubling device 2 is connected to the beam splitter prism 3. The beam splitter prism 3 is connected to the exit window 7 and the beam terminator 8, respectively. The specific operation is carried out according to the following steps: a. After the ultraviolet laser emitted by the ultraviolet laser passes through the beam shaping system 4, the spatial intensity distribution of the beam is matched with the frequency doubling device 2. The beam enters the vacuum cavity 5 in the nitrogen or inert gas environment through the incident window 6 and passes through the frequency doubling device 2. b. The frequency doubling device 2 is placed in the light transmission direction with the phase matching angle. Frequency doubling occurs in the frequency doubling device 2 to generate deep ultraviolet frequency-doubled laser. Due to dispersion, the remaining ultraviolet fundamental frequency light passing through the frequency doubling device 2 and the output deep ultraviolet frequency-doubled light pass through the beam splitting prism 3 placed at the Brewster angle of the deep ultraviolet frequency-doubled light. The ultraviolet fundamental frequency beam and the deep ultraviolet frequency-doubled beam are separated by a deflection angle of 5-30°. c. The remaining ultraviolet fundamental frequency laser is collected by beam terminator 8, and the deep ultraviolet laser is emitted through the emission window 7 set in the transmission direction. Example 2

[0024] according to Figure 2 This embodiment is a schematic diagram of a 193nm wavelength tunable solid-state deep ultraviolet laser with direct frequency doubling output from NH4B4O6F deep ultraviolet laser: In this embodiment, a Ti:sapphire laser 9 outputs a 773nm laser. Then, a first frequency converter 10, consisting of a commercial lithium triborate crystal with a tangential phase matching angle of θ=90° and φ=34° and an anti-reflection coating on the light-transmitting surface at 773nm and 386nm, and a temperature control module with a temperature control temperature of 25°C, is used to convert the 773nm laser into a 386nm laser. The 773nm laser is then reflected to the first beam terminator 12 by a first beam splitter 11, and the 386nm ultraviolet fundamental frequency laser is transmitted through the first beam splitter 11. After passing through the first beam shaping system 13, the spatial intensity distribution of the beam is matched with the first frequency doubling device 14, and the beam is incident on and passes through the first frequency doubling device 14. Since the 193nm laser has almost no loss in air, a vacuum cavity is not required in this embodiment. The first frequency doubling device 14 is placed with a phase matching angle θ=90° and φ=54° in the light transmission direction. Frequency doubling occurs in the first frequency doubling device 14 to generate deep ultraviolet frequency doubling laser. Due to dispersion, after the remaining ultraviolet fundamental frequency light and the output deep ultraviolet frequency doubling light pass through the first beam splitting prism 15, the ultraviolet fundamental frequency beam and the deep ultraviolet frequency doubling beam are separated by a deflection angle of 5-30°. The remaining ultraviolet fundamental frequency laser is collected by the second beam terminator 16. Example 3

[0025] according to Figure 3 This embodiment is a schematic diagram of the structure of a 177.3nm solid-state deep ultraviolet laser with direct frequency doubling output from NH4B4O6F: In this embodiment, a neodymium-doped yttrium aluminum garnet laser 17 outputs a 1064nm laser. A second frequency converter 18, consisting of a commercially available lithium triborate crystal with a tangential phase matching angle θ=90° and φ=0° and an antireflection coating on the light-transmitting surface at 1064nm and 532nm, and a temperature control module with a temperature range of 148-151℃, converts the 1064nm laser into a 532nm laser. The remaining 1064nm and 532nm lasers are incident with a tangential phase matching angle θ=44°. A third frequency converter 19, consisting of a commercial lithium triborate crystal with an anti-reflection coating on the light-transmitting surface at φ=90° and a temperature control module at 47°C, converts the 1064nm and 532nm lasers into a 355nm laser. The 1064nm and 532nm lasers are then reflected by a second beam splitter 20 to a third beam terminator 21. The 355nm ultraviolet fundamental frequency laser passes through the second beam splitter 20. After passing through a second beam shaping system 22, the spatial intensity distribution of the 355nm ultraviolet laser beam is matched with a second frequency doubling device 24. It then passes through a first incident window 23 and enters a first vacuum cavity 25 in a nitrogen or inert gas environment, and is incident on and passes through the second frequency doubling device 24. The second frequency doubling device 24 has a phase matching angle θ=90°. With the light transmission direction φ=63°, the deep ultraviolet frequency-doubled laser is generated by frequency doubling in the second frequency doubling device 24. Due to dispersion, the remaining ultraviolet fundamental frequency light and the output deep ultraviolet frequency-doubled light are separated by a deflection angle of 5-30° after passing through the second beam splitter prism 26. The remaining ultraviolet fundamental frequency laser is collected by the fourth beam terminator 28, and the deep ultraviolet laser is emitted through the first emission window 27 set in the transmission direction. Example 4

[0026] according to Figure 4This embodiment is a schematic diagram of a 159-205nm wavelength tunable solid-state deep ultraviolet laser with direct frequency doubling output from NH4B4O6F: This embodiment employs a 1064nm Q-switched pulsed laser resonator composed of a 1064nm high-reflectivity mirror 29, a neodymium-doped yttrium vanadate laser crystal 30, a potassium dihydrogen phosphate electro-optic Q-switched crystal 31, and a 1064nm partial reflector 32. The laser crystal is excited by optical pumping or heat pumping to output a 1064nm pulsed laser. A phase-matching angle θ = 90° is used in the tangential direction. A fourth frequency converter 33, consisting of a commercial lithium triborate crystal 37 with an anti-reflection coating on the light-transmitting surface at 1064nm & 532nm and a temperature control module with a temperature of 148-151℃, converts the 1064nm laser into a 532nm laser. The 1064nm laser is then reflected by a third beam splitter 34 to a fifth beam terminator 35. The 532nm laser is transmitted through the third beam splitter 34. The 532nm laser is incident on a lens 36 that has high reflectivity to 640-820nm and is enclosed in a temperature control module with a temperature of 90-120℃. The tangential phase matching angle is θ=90°. A commercial lithium triborate crystal 37 with a φ=0° aperture and an anti-reflection coating on its light-transmitting surface at 532nm & 640-820nm, along with a lens 38 that partially reflects the 640-820nm wavelength, forms a fifth frequency converter. This converter transforms the 532nm laser into tunable lasers with wavelengths of 640-820nm and 1.6-3.1μm. These tunable lasers are then reflected by a fourth beam splitter 39 to a sixth beam terminator 40. The tunable laser with wavelengths of 640-820nm is transmitted through the fourth beam splitter 39. The incident light is emitted from a commercial lithium triborate crystal 37 with a tangential phase matching angle θ=90° and a φ=34° aperture and an anti-reflection coating on its light-transmitting surface at 773nm & 386nm. A sixth frequency converter 41, consisting of a lithium borate crystal and a temperature control module with a temperature of 25°C, converts a tunable laser with a wavelength of 640-820nm into a tunable laser with a wavelength of 318-410nm as the ultraviolet fundamental frequency laser. The sixth frequency converter 41 achieves wavelength tuning by rotating the crystal. After passing through the third beam shaping system 42, the spatial intensity distribution of the 318-410nm tunable ultraviolet fundamental frequency laser is matched with the third frequency doubling device 44. After passing through the second incident window 43, it enters the second vacuum cavity 45 in a nitrogen or inert gas environment and is incident on and passes through the third frequency doubling device 44. The third frequency doubling device 44 has a phase matching angle θ=90°. With the light transmission direction φ=75°, the third frequency doubling device 44 generates a tunable deep ultraviolet frequency-doubled laser with a wavelength of 159-205nm. Due to dispersion, the remaining ultraviolet fundamental frequency light and the output deep ultraviolet frequency-doubled light are separated by a deflection angle of 5-30° after passing through the third beam splitter prism 46. The remaining ultraviolet fundamental frequency laser is collected by the seventh beam terminator 48, and the deep ultraviolet laser is emitted through the second emission window 47 set in the transmission direction.

Claims

1. A deep ultraviolet solid-state laser based on NH4B4O6F crystal, characterized in that, The laser consists of an ultraviolet laser (1), a frequency doubling device (2), a beam splitter prism (3), a beam shaping system (4), a vacuum cavity (5), an entrance window (6), an exit window (7), and a beam terminator (8). The ultraviolet laser (1) is connected in series with the frequency doubling device (2) through the beam shaping system (4), the vacuum cavity (5), and the entrance window (6). The frequency doubling device (2) is connected to the beam splitter prism (3). The beam splitter prism (3) is connected to the exit window (7) and the beam terminator (8) respectively. The specific operation is carried out according to the following steps: a. The ultraviolet laser (1) emits ultraviolet laser. After passing through the beam shaping system (4), the spatial intensity distribution of the beam is matched with the frequency doubling device (2). It enters the vacuum cavity (5) of nitrogen or inert gas environment through the incident window (6) and passes through the frequency doubling device (2). b. The frequency doubling device (2) is made of NH4B4O6F crystal, which can directly double the frequency to achieve deep ultraviolet output of 159-205nm. It is placed in the light transmission direction with the phase matching angle. In the frequency doubling device (2), the frequency is doubled to generate deep ultraviolet frequency doubled laser. Due to dispersion, the remaining ultraviolet fundamental frequency light passing through the frequency doubling device (2) and the output deep ultraviolet frequency doubled light pass through the beam splitting prism (3) placed with the Brewster angle of the deep ultraviolet frequency doubled light. The ultraviolet fundamental frequency beam and the deep ultraviolet frequency doubled beam are separated by a deflection angle of 5-30°. c. The remaining ultraviolet fundamental frequency laser is collected by the beam terminator (8), and the deep ultraviolet laser is emitted through the emission window (7) set in the transmission direction.

2. The deep ultraviolet solid-state laser based on NH4B4O6F crystal according to claim 1, characterized in that, The ultraviolet laser (1) includes a first ultraviolet laser consisting of a Ti:sapphire laser (9), a first frequency converter (10) and a first beam splitter (11); Or a second ultraviolet laser consisting of a neodymium-doped yttrium aluminum garnet laser (17), a second frequency converter (18), a third frequency converter (19), and a second beam splitter (20); Alternatively, a third ultraviolet laser may be composed of a 1064nm high-reflectivity mirror (29), a neodymium-doped yttrium vanadate laser crystal (30), a potassium dihydrogen phosphate electro-optic Q-switching crystal (31), a 1064nm partial reflector (32), a fourth frequency converter (33), a third beam splitter (34), a 640-820nm high-reflectivity lens (36), a lithium triborate crystal (37), a 640-820nm partial reflector lens (38), a fourth beam splitter (39), and a sixth frequency converter (41).

3. A deep ultraviolet solid-state laser based on NH4B4O6F crystal according to claim 1, characterized in that, The ultraviolet laser (1) consists of an infrared fundamental frequency light source and several frequency converters; the infrared fundamental frequency light source is a 640-950nm Ti:sapphire laser, a 1030nm-1080nm ytterbium laser, a 1064nm or 1.3μm neodymium laser, which generates and outputs an ultraviolet laser with a wavelength of 318-410nm through one or more frequency converters that perform frequency doubling, summing, optical parameter generation, optical parameter amplification, optical parameter oscillation and difference frequency.

4. A deep ultraviolet solid-state laser based on NH4B4O6F crystal according to claim 1, characterized in that, The frequency doubling device (2) includes a first frequency doubling device (14), a second frequency doubling device (24), and a third frequency doubling device (44). The frequency doubling device (2) is made of NH4B4O6F crystal, which can directly double the frequency to achieve 159-205nm deep ultraviolet output. The light transmission direction of the frequency doubling device (2) is the phase matching direction of the ultraviolet laser frequency doubling to 159-205nm deep ultraviolet laser. The incident surface of the frequency doubling device (2) is processed to be normal incident or Brewster angle incident of ultraviolet pump light, and the exit surface is processed to be parallel to the incident surface or Brewster angle exit of deep ultraviolet frequency doubling light. The phase matching cutting angle of the 159-205nm deep ultraviolet laser output is 50°-90°.

5. A deep ultraviolet solid-state laser based on NH4B4O6F crystal according to claim 1, characterized in that, The beam splitter (3) includes a first beam splitter (15), a second beam splitter (26) and a third beam splitter (46); the beam splitter (3) is composed of a material with high transmittance in the deep ultraviolet band, the laser incident surface and the exit surface are in the Brewster angle direction of the output deep ultraviolet laser, and both sides are polished; the material of the beam splitter (3) is silicon dioxide or calcium fluoride, and the apex angle used for beam splitting is 56.1-59.6°.

6. A deep ultraviolet solid-state laser based on NH4B4O6F crystal according to claim 1, characterized in that, The beam shaping system (4) includes a first beam shaping system (13), a second beam shaping system (22) and a third beam shaping system (42); the beam shaping system (4) is composed of spherical, cylindrical, aspherical lenses, spherical, cylindrical, aspherical mirrors or super-Gaussian shaping lenses, and is used to shape the spatial profile of the ultraviolet laser beam.

7. A deep ultraviolet solid-state laser based on NH4B4O6F crystal according to claim 1, characterized in that, The vacuum cavity (5) includes a first vacuum cavity (25) and a second vacuum cavity (45). The vacuum cavity (5) consists of a sealed cavity, a cavity light transmission window, and a vacuum pump. The sealed cavity is evacuated or filled with nitrogen or inert gas to ensure that the frequency doubling device (2) outputs deep ultraviolet laser in a vacuum or nitrogen / inert gas environment. The light transmission window of the vacuum cavity (5) is made of a material with high transmittance to ultraviolet laser and deep ultraviolet frequency doubling laser. The ultraviolet laser emitted by the ultraviolet laser (1) enters the vacuum cavity (5) through the light transmission window at one end of the sealed cavity. It enters the frequency doubling device (2) by normal incidence or Brewster angle incidence, generating and outputting 159-205nm deep ultraviolet laser, which is output from the exit window on the vacuum cavity (5) set in its propagation direction.

8. A deep ultraviolet solid-state laser based on NH4B4O6F crystal according to claim 1, characterized in that, The incident window (6) includes a first incident window (23) and a second incident window (43); the exit window (7) includes a first exit window (27) and a second exit window (47); the beam terminator (8) includes a first beam terminator (12), a second beam terminator (16), a third beam terminator (21), a fourth beam terminator (28), a fifth beam terminator (35), a sixth beam terminator (40), and a seventh beam terminator (48).

9. A deep ultraviolet solid-state laser based on NH4B4O6F crystal according to claim 1, characterized in that, The frequency doubling device (2) is processed according to the phase matching angle direction of the output laser and the light-transmitting surface is polished.

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