Deep ultraviolet solid laser based on NH4B4O6F crystal

Abstract

The invention provides a deep ultraviolet solid laser based on an NH4B4O6F crystal, which is composed of an ultraviolet laser, a frequency doubling device, a light splitting prism, a light beam shaping system, a vacuum cavity, an incident window sheet, an emergent window sheet and a light beam terminator, and is characterized in that a plurality of frequency converters are used for converting near-infrared laser into 318-410nm ultraviolet laser; a light beam shaping system is adopted to shape ultraviolet laser into a space light beam contour beneficial to improving frequency doubling output, the ultraviolet laser is emitted into a frequency doubling device arranged in a vacuum cavity system, and 159-205 nm deep ultraviolet laser is output through direct frequency doubling. The laser has the advantages of being simple in system, convenient to operate, stable in laser output, compact, small in size, low in cost and the like, and can be applied to the fields of frontier scientific research equipment, precision machining, optical detection and the like.

Description

Technical Field

[0001] The present invention relates to the field of solid laser technology, and mainly relates to a deep ultraviolet solid laser based on NH4B4O6F crystal, which is a device capable of realizing solid deep ultraviolet laser with a wavelength of 159 - 205nm through direct frequency doubling. Background Art

[0002] Lasers in the deep ultraviolet band (<200nm) have been widely used in frontier scientific fields such as atomic clock cooling, precision machining, lithography, and photoelectron spectrometers due to their advantages of high single - photon energy, short optical period, and high spatial resolution, and have important application values. Currently, the most effective way to achieve high - quality deep ultraviolet laser output is the deep ultraviolet solid laser technology based on nonlinear frequency up - conversion. This technology combines the advantages of good beam quality and small volume of solid lasers 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 the commonly used large - volume and high - cost gas - medium ultraviolet excimer lasers, solid lasers have been widely used due to their advantages of reasonable price, high throughput, and small volume.

[0003] The core of the deep ultraviolet solid laser technology is the nonlinear optical crystal used for frequency conversion. The nonlinear optical crystal in the deep ultraviolet band needs to meet the basic requirements of being transparent in the deep ultraviolet band, capable of achieving phase matching, and having a sufficient nonlinear optical coefficient. Currently, the only crystal that can meet the above requirements and be used in the deep ultraviolet all - solid - state laser technology realized by direct frequency doubling and obtain practical applications is the KBe2BO3F2 (KBBF) family of crystals. However, it has a serious layered growth habit, which brings difficulties to the growth and processing of the crystal, and can only achieve deep ultraviolet laser output through prism coupling technology, which is not conducive to industrialization. Generally speaking, there are few materials that can meet the requirements of deep ultraviolet nonlinear optical materials, making it difficult to further promote the development of deep ultraviolet lasers.

[0004] The Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences first discovered the NH4B4O6F crystal internationally (Guoqiang Shi, Ying Wang, Fangfang Zhang, Bingbing Zhang, Zhihua Yang, Xueling Hou, Shilie Pan, Kenneth R. Poeppelmeier, "Finding the Next Deep-Ultraviolet Nonlinear Optical Material: NH4B4O6F", Journal of the American Chemical Society, 2017(139): 10645). A number of technologies such as the nonlinear optical crystal growth equipment and crystal growth technology of this crystal were developed. The raw material of this crystal does not contain highly toxic beryllium oxide, has no layered growth habit, the band gap is 7.95 eV, the deep ultraviolet transparent range can be as short as 156 nm, and the shortest phase matching wavelength can reach 158 nm. The nonlinear optical coefficient d 11 = 1 pm / V, meeting all the requirements of deep ultraviolet nonlinear optical crystals.

[0005] In summary, the NH4B4O6F crystal can achieve direct frequency doubling output in the deep ultraviolet range of 159 - 205 nm, enabling a laser device with high power, high efficiency, compact integration, and small volume, which is conducive to industrialization. Summary of the Invention

[0006] The object of the present invention is to propose a deep ultraviolet solid-state laser based on the NH4B4O6F crystal to address the problem that it is difficult to achieve 159 - 205 nm solid deep ultraviolet lasers. This laser is composed of an ultraviolet laser, a frequency doubling device, a beam splitting prism, a beam shaping system, a vacuum chamber, an incident window plate, an exit window plate, and a beam terminator. A number of frequency converters are used to convert near-infrared laser into ultraviolet laser with a wavelength of 318 - 410 nm. The beam shaping system is used to shape the ultraviolet laser into a spatial beam profile that is conducive to improving the frequency doubling output, and the ultraviolet laser is incident on the frequency doubling device placed inside the vacuum chamber system to directly generate 159 - 205 nm deep ultraviolet laser through frequency doubling. This laser has the advantages of a simple system, convenient operation, stable laser output, compact volume, and low cost, and can be applied to fields such as cutting-edge scientific research equipment, precision machining, and optical detection.

[0007] A deep ultraviolet solid-state laser based on an NH4B4O6F crystal according to the present invention. The laser is composed of an ultraviolet laser (1), a frequency doubling device (2), a beam splitting prism (3), a beam shaping system (4), a vacuum chamber (5), an incident window plate (6), an exit window plate (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 chamber (5), and the incident window plate (6). The frequency doubling device (2) is connected to the beam splitting prism (3), and the beam splitting prism (3) is respectively connected to the exit window plate (7) and the beam terminator (8). 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 matches that of the frequency doubling device (2), and enters the vacuum chamber (5) with a nitrogen or inert gas environment through the incident window plate (6), and enters and passes through the frequency doubling device (2); b. The frequency doubling device (2) is placed in the light passing direction at the phase matching angle. Second harmonic generation occurs in the frequency doubling device (2) to generate deep ultraviolet second harmonic laser. Due to dispersion, the remaining ultraviolet fundamental frequency light passing through the frequency doubling device (2) and the output deep ultraviolet second harmonic light pass through the beam splitting prism (3) placed at the Brewster angle of the deep ultraviolet second harmonic light, and the ultraviolet fundamental frequency beam and the deep ultraviolet second harmonic beam are separated at 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 exits through the exit window plate (7) arranged in the transmission direction.

[0008] The ultraviolet laser (1) includes a first ultraviolet laser composed of a titanium sapphire laser (9), a first frequency converter (10), and a first beam splitter (11); or a second ultraviolet laser composed 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); or a third ultraviolet laser composed of a 1064 nm high reflector (29), a neodymium-doped yttrium vanadate laser crystal (30), a potassium dihydrogen phosphate electro-optic Q-switching crystal (31), a 1064 nm partial reflector (32), a fourth frequency converter (33), a third beam splitter (34), a 640 - 820 nm highly reflective lens (36), a lithium triborate crystal (37), a 640 - 820 nm partially reflective lens (38), a fourth beam splitter (39), and a sixth frequency converter (41).

[0009] The ultraviolet laser (1) described above is composed of an infrared fundamental frequency light source and several frequency converters; the infrared fundamental frequency light source is a titanium sapphire laser with a wavelength of 640 - 950 nm, a ytterbium laser with a wavelength of 1030 nm - 1080 nm, or a neodymium laser with a wavelength of 1064 nm or 1.3 μm. Through one - stage or multi - stage frequency doubling, sum - frequency generation, optical parametric generation, optical parametric amplification, optical parametric oscillation, and difference - frequency generation frequency converters, ultraviolet laser with a wavelength in the range of 318 - 410 nm is generated and output.

[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 that can directly achieve deep ultraviolet output of 159 - 205 nm through frequency doubling. The light - passing direction of the frequency doubling device (2) is the phase - matching direction for ultraviolet laser frequency doubling to 159 - 205 nm deep ultraviolet laser. The incident surface of the frequency doubling device (2) is processed to be normal incidence or incidence at the Brewster angle of the ultraviolet pump light, and the exit surface is processed to be parallel to the incident surface or exit at the Brewster angle of the deep ultraviolet frequency - doubled light; the phase - matching cutting angle of the 159 - 205 nm deep ultraviolet laser output is 50° - 90°.

[0011] The beam - splitting prism (3) includes a first beam - splitting prism (15), a second beam - splitting prism (26), and a third beam - splitting prism (46); the beam - splitting prism (3) is composed of materials with high transmittance in the deep ultraviolet band. The laser incident surface and the exit surface are in the direction of the Brewster angle of the output deep ultraviolet laser, and both surfaces are polished; the material of the beam - splitting prism (3) is silica or calcium fluoride, and the angle of the apex 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 for shaping 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-transmitting window, and a vacuum pump. The inside of the sealed cavity is evacuated or filled with nitrogen or inert gas to ensure that the frequency doubling device (2) outputs deep ultraviolet laser by frequency doubling in a vacuum or nitrogen or inert gas environment. The light-transmitting window of the vacuum cavity (5) is composed 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) from the light-transmitting window at one end of the sealed cavity, enters the frequency doubling device (2) by normal incidence or Brewster angle incidence, generates and outputs deep ultraviolet laser with a wavelength of 159 - 205 nm, and outputs from the output window on the vacuum cavity (5) set in its propagation direction.

[0014] The incident window plate (6) includes a first incident window plate (23) and a second incident window plate (43); the output window plate (7) includes a first output window plate (27) and a second output window plate (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 processed from an NH4B4O6F crystal, processed according to the phase matching angle direction of the output laser, and the light-transmitting surface is polished.

[0016] A deep ultraviolet solid-state laser based on NH4B4O6F crystal according to the present invention. The laser includes an ultraviolet laser (1), a frequency doubling device (2), a beam splitting prism (3), and a beam shaping system (4). Since the loss of light with wavelengths in the range of 159 - 190 nm in air is severe, a vacuum chamber system (5) is required. The ultraviolet laser generates ultraviolet laser with a wavelength of 318 - 410 nm by using non-linear frequency conversion methods with titanium sapphire laser at 640 - 950 nm, ytterbium laser at 1030 - 1080 nm, neodymium laser at 1064 nm or 1.3 μm. The frequency doubling device (2) is made of NH4B4O6F crystal that can directly double the frequency to achieve deep ultraviolet output in the range of 159 - 205 nm. The light passing direction of the frequency doubling device (2) is the phase matching direction for doubling the ultraviolet laser to deep ultraviolet laser in the range of 159 - 205 nm. The incident surface of the frequency doubling device (2) is processed to be normal incidence or incidence at the Brewster angle of the ultraviolet pump light, and the exit surface is processed to be parallel to the incident surface or exit at the Brewster angle of the deep ultraviolet frequency doubled light. 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. The beam splitting prism (3) is composed of materials with high transmittance in the deep ultraviolet band. The laser incident surface and the exit surface are in the direction of 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 chamber system (5) consists of a sealed chamber, a chamber light passing window, and a vacuum pump. The inside of the sealed chamber is evacuated or filled with nitrogen or inert gas to ensure that the frequency doubling device (2) doubles the frequency and outputs deep ultraviolet laser in a vacuum or nitrogen or inert gas environment, preventing the deep ultraviolet laser output by frequency doubling from being absorbed and lost by oxygen or water vapor. The chamber light passing window is composed of materials with high transmittance for ultraviolet pump laser and deep ultraviolet frequency doubled laser. The ultraviolet laser emitted by the ultraviolet laser enters the chamber through the light passing window at one end of the sealed chamber and enters the frequency doubling device (2) by normal incidence or incidence at the Brewster angle, generating and outputting deep ultraviolet laser in the range of 159 - 205 nm. The ultraviolet pump light is collected by a beam stopper, and the deep ultraviolet laser is output through the exit window provided in its propagation direction.

[0017] The ultraviolet laser described above 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 reflector for fundamental frequency laser, a partial reflector for fundamental frequency laser, and a laser gain medium. The laser gain medium is titanium sapphire crystal, crystal doped with neodymium or ytterbium, glass, ceramic, or optical fiber material. The frequency converter mainly includes a frequency doubling 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, with the Chinese name of ammonium fluoroborate crystal, the chemical formula of NH4B4O6F, the molecular weight of 176.28, belonging to the orthorhombic crystal system, and the space group is Pna 21, and the unit cell parameters are a = 7.602(2) Å, b = 11.197(3) Å, c = 6.5952(19) Å, α = 90°, β = 90°, γ = 90°.

[0019] For the described NH4B4O6F crystal, the phase matching cutting angle of the output 159 - 205 nm deep ultraviolet laser is 50° - 90°.

[0020] The material of the beam splitting prism is silica or calcium fluoride, and the angle of the apex angle for beam splitting is 56.1 - 59.6°. Description of the Drawings

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

[0022] The following further describes the present invention with reference to embodiments. It should be noted that the given embodiments cannot be used as a limitation to the protection scope of the present invention, and any improvement made on the basis of the present invention does not violate the spirit of the present invention. The components or devices used in the present invention are commercially available unless otherwise specified. Example 1

[0023] Figure 1Schematic structural diagram of the device of the present invention: A deep ultraviolet solid laser based on an NH4B4O6F crystal according to the present invention, the laser is composed of an ultraviolet laser 1, a frequency doubling device 2, a beam splitting prism 3, a beam shaping system 4, a vacuum chamber 5, an incident window plate 6, an exit window plate 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 chamber 5 and the incident window plate 6. The frequency doubling device 2 is connected to the beam splitting prism 3, and the beam splitting prism 3 is respectively connected to the exit window plate 7 and the beam terminator 8. 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 matches that of the frequency doubling device 2, and enters the vacuum chamber 5 in an environment of nitrogen or inert gas through the incident window plate 6, and is incident on and passes through the frequency doubling device 2; b. The frequency doubling device 2 is placed in the optical passing direction at 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, and the ultraviolet fundamental frequency beam and the deep ultraviolet frequency doubled beam are separated at 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 exits through the exit window plate 7 arranged in the transmission direction. Embodiment 2

[0024] According to Figure 2 , this embodiment is a schematic structural diagram of a 193nm wavelength tunable solid deep ultraviolet laser with direct frequency doubling output of NH4B4O6F deep ultraviolet: In this embodiment, a titanium sapphire laser 9 is used to output 773nm laser, and then a first frequency converter 10 composed of a commercial lithium triborate crystal with a tangential phase matching angle θ = 90° and φ = 34° and an antireflection coating @773nm&386nm on the optical passing surface and a temperature control module with a controlled temperature of 25°C is used to convert the 773nm laser into 386nm laser, and the 773nm laser is reflected to the first beam terminator 12 through the first beam splitter 11, and the 386nm ultraviolet fundamental frequency laser transmits through the first beam splitter 11; After passing through the first beam shaping system 13, the spatial intensity distribution of the beam matches that of the first frequency doubling device 14, and the beam is incident on and passes through the first frequency doubling device 14. Since the 193 nm laser has almost no loss in air, a vacuum chamber is not required in this embodiment. The first frequency doubling device 14 is arranged with a light passing direction of phase matching angles θ = 90° and φ = 54°. Frequency doubling occurs in the first frequency doubling device 14 to generate deep ultraviolet frequency doubled laser. Due to dispersion, after the remaining ultraviolet fundamental frequency light and the output deep ultraviolet frequency doubled light pass through the first beam splitting prism 15, the ultraviolet fundamental frequency beam and the deep ultraviolet frequency doubled beam are separated at a deflection angle of 5 - 30°. The remaining ultraviolet fundamental frequency laser is collected by the second beam terminator 16. Embodiment 3

[0025] According to Figure 3 , this embodiment is a schematic structural diagram of a 177.3 nm solid deep ultraviolet laser with direct frequency doubling output of NH4B4O6F deep ultraviolet: In this embodiment, a neodymium-doped yttrium aluminum garnet laser 17 is used to output 1064 nm laser. Then, a second frequency converter 18 composed of a commercial lithium triborate crystal with a tangential phase matching angle θ = 90° and φ = 0° and an antireflection coating @1064 nm & 532 nm on the light passing surface and a temperature control module with a controlled temperature of 148 - 151 °C is used to convert the 1064 nm laser into 532 nm laser. The remaining 1064 nm laser and 532 nm laser are incident on a third frequency converter 19 composed of a commercial lithium triborate crystal with a tangential phase matching angle θ = 44° and φ = 90° and an antireflection coating @1064 nm & 532 nm & 355 nm on the light passing surface and a temperature control module at a temperature of 47 °C to convert the 1064 nm laser and 532 nm laser into 355 nm laser. The 1064 nm laser and 532 nm laser are reflected to the third beam terminator 21 through the second beam splitter 20. The ultraviolet fundamental frequency laser with a wavelength of 355 nm passes through the second beam splitter 20. The 355 nm ultraviolet laser passes through the second beam shaping system 22, and the spatial intensity distribution of the beam matches that of the second frequency doubling device 24. It enters the first vacuum chamber 25 in a nitrogen or inert gas environment through the first incident window plate 23, and is incident on and passes through the second frequency doubling device 24. The second frequency doubling device 24 is arranged with a light passing direction of phase matching angles θ = 90° and φ = 63°. Frequency doubling occurs in the second frequency doubling device 24 to generate deep ultraviolet frequency doubled laser. Due to dispersion, after the remaining ultraviolet fundamental frequency light and the output deep ultraviolet frequency doubled light pass through the second beam splitting prism 26, the ultraviolet fundamental frequency beam and the deep ultraviolet frequency doubled beam are separated at a deflection angle of 5 - 30°. The remaining ultraviolet fundamental frequency laser is collected by the fourth beam terminator 28, and the deep ultraviolet laser exits through the first exit window plate 27 arranged in the transmission direction. Embodiment 4

[0026] According to Figure 4, This embodiment is a schematic structural diagram of a 159 - 205 nm wavelength tunable solid deep ultraviolet laser with direct second harmonic generation output of NH4B4O6F: This embodiment adopts a 1064nm Q-switched pulsed laser resonator composed of a 1064nm high reflector 29, a neodymium-doped yttrium vanadate laser crystal 30, a potassium dihydrogen phosphate electro-optic Q-switching crystal 31, and a 1064nm partial reflector 32. The laser crystal is excited by an optical pump or a heat pump to output 1064nm pulsed laser. Then, a fourth frequency converter 33 composed of a commercial lithium triborate crystal 37 with a tangential phase matching angle θ = 90° φ = 0° and an antireflection coating on the light-passing surface @1064nm&532nm and a temperature control module at 148 - 151°C is used to convert the 1064nm laser into 532nm laser. The 1064nm laser is reflected to a fifth beam terminator 35 through a third beam splitter 34. The laser with a wavelength of 532nm transmits through the third beam splitter 34 and enters a fifth frequency converter composed of a lens 36 with high reflectivity for 640 - 820nm, a commercial lithium triborate crystal 37 with a tangential phase matching angle θ = 90° φ = 0° and an antireflection coating on the light-passing surface @532nm&640 - 820nm and wrapped in a temperature control module with a controlled temperature of 90 - 120°C, and a lens 38 with partial reflection for 640 - 820nm. The 532nm laser is converted into tunable lasers with wavelengths of 640 - 820nm and 1.6 - 3.1μm, and the 532nm laser and the 1.6 - 3.1μm wavelength tunable laser are reflected to a sixth beam terminator 40 through a fourth beam splitter 39. The tunable laser with a wavelength of 640 - 820nm transmits through the fourth beam splitter 39 and enters a sixth frequency converter 41 composed of a commercial lithium triborate crystal with a tangential phase matching angle θ = 90° φ = 34° and an antireflection coating on the light-passing surface @773nm&386nm and a temperature control module at 25°C. The tunable laser with a wavelength of 640 - 820nm is converted into a tunable laser with a wavelength of 318 - 410nm as the ultraviolet fundamental frequency laser. The sixth frequency converter 41 realizes wavelength tuning by rotating the direction of the crystal. The spatial intensity distribution of the beam of the 318 - 410nm wavelength tunable ultraviolet fundamental frequency laser matches that of the third harmonic generation device 44 after passing through the third beam shaping system 42. It enters a second vacuum chamber 45 in a nitrogen or inert gas environment through a second incident window plate 43 and enters and passes through the third harmonic generation device 44. The third harmonic generation device 44 is placed with a light-passing direction of a phase matching angle θ = 90° φ = 75°. Second harmonic generation occurs in the third harmonic generation device 44 to generate a tunable deep ultraviolet second harmonic laser with a wavelength of 159 - 205nm. Due to dispersion, after the remaining ultraviolet fundamental frequency light and the output deep ultraviolet second harmonic light pass through a third spectroscopic prism 46, the ultraviolet fundamental frequency beam and the deep ultraviolet second harmonic beam are separated at a deflection angle of 5 - 30°. The remaining ultraviolet fundamental frequency laser is collected by a seventh beam terminator 48, and the deep ultraviolet laser exits through a second exit window plate 47 arranged in the transmission direction.

Claims

1. A deep ultraviolet solid-state laser based on NH4B4O6F crystal, characterized in that: The laser is composed 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 incident 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 incident window (6). The frequency doubling device (2) is connected to the beam splitter prism (3). The beam splitter prism (3) is respectively connected to the exit window (7) and the beam terminator (8). The specific operation is performed according to the following steps: a. The ultraviolet laser (1) emits ultraviolet laser light, and after the ultraviolet laser light passes through the beam shaping system (4), the spatial intensity distribution of the beam matches the frequency doubling device (2), and the beam enters the vacuum cavity (5) in a nitrogen or inert gas environment through the incident window (6), and then enters and passes through the frequency doubling device (2); b. The frequency doubling device (2) is arranged in the light transmission direction of the phase matching angle, and frequency doubling occurs in the frequency doubling device (2) to generate 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 splitter (3) arranged at the Brewster angle of the deep ultraviolet frequency doubling light, and the ultraviolet fundamental frequency beam and the deep ultraviolet frequency doubling beam are separated at a deflection angle of 5-30°; c. The remaining ultraviolet fundamental frequency laser light is collected by the beam terminator (8), and the deep ultraviolet laser light is emitted through the emission window (7) arranged in the transmission direction.

2. The deep ultraviolet solid laser based on NH4B4O6F crystal according to claim 1, characterized in that: The ultraviolet laser (1) comprises a first ultraviolet laser composed of a titanium sapphire laser (9), a first frequency converter (10) and a first beam splitter (11); or a second ultraviolet laser composed 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); Or a third ultraviolet laser consisting of a 1064nm high reflection mirror (29), a neodymium-doped yttrium vanadate laser crystal (30), a potassium dihydrogen phosphate electro-optical Q-switched crystal (31), a 1064nm partial reflection mirror (32), a fourth frequency converter (33), a third beam splitter (34), a 640-820nm high reflection lens (36), a lithium triborate crystal (37), a 640-820nm partial reflection lens (38), a fourth beam splitter (39) and a sixth frequency converter (41).

3. The deep ultraviolet solid laser based on NH4B4O6F crystal according to claim 1, characterized in that: The ultraviolet laser (1) is composed of an infrared fundamental frequency light source and a plurality of frequency converters; the infrared fundamental frequency light source is a 640-950nm titanium sapphire laser, a 1030nm-1080nm ytterbium laser, a 1064nm or 1.3μm neodymium laser, and generates and outputs an ultraviolet laser with a wavelength of 318-410nm through one or more stages of frequency doubling, sum frequency, optical parametric generation, optical parametric amplification, optical parametric oscillation, and a frequency converter of difference frequency.

4. The deep ultraviolet solid laser based on NH4B4O6F crystal according to claim 1, characterized in that: The frequency doubling device (2) comprises 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 capable of directly doubling the frequency to realize 159-205nm deep ultraviolet output; the light transmission direction of the frequency doubling device (2) is the phase matching direction of ultraviolet laser frequency doubling to 159-205nm deep ultraviolet laser; the incident surface of the frequency doubling device (2) is processed to be normal incidence or Brewster angle incidence of ultraviolet pump light; 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 output 159-205nm deep ultraviolet laser is 50°-90°.

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

6. The deep ultraviolet solid laser based on NH4B4O6F crystal according to claim 1, characterized in that: The beam shaping system (4) comprises 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 a spherical, cylindrical, aspherical lens, a spherical, cylindrical, aspherical reflector or a super Gaussian shaping lens, and is used for shaping the spatial profile of the ultraviolet laser beam.

7. The deep ultraviolet solid laser based on NH4B4O6F crystal according to claim 1, characterized in that: The vacuum cavity (5) comprises a first vacuum cavity (25) and a second vacuum cavity (45); the vacuum cavity (5) comprises a sealed cavity, a cavity light-transmitting window, and a vacuum pump; the sealed cavity is evacuated or filled with nitrogen or an inert gas to ensure that the frequency-doubling device (2) outputs deep ultraviolet laser light in a vacuum or nitrogen or inert gas environment; the light-transmitting window of the vacuum cavity (5) is made of a material with high transmittance to ultraviolet laser light and deep ultraviolet frequency-doubling laser light; the ultraviolet laser light emitted by the ultraviolet laser (1) enters the vacuum cavity (5) through the light-transmitting window at one end of the sealed cavity, enters the frequency-doubling device (2) by normal incidence or Brewster angle incidence, generates and outputs 159-205 nm deep ultraviolet laser light, and outputs the deep ultraviolet laser light from an exit window arranged on the vacuum cavity (5) in the propagation direction thereof.

8. The deep ultraviolet solid laser based on NH4B4O6F crystal according to claim 1, characterized in that: The incident window plate (6) comprises a first incident window plate (23) and a second incident window plate (43); the exit window plate (7) comprises a first exit window plate (27) and a second exit window plate (47); and the beam terminator (8) comprises 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. The deep ultraviolet solid laser based on NH4B4O6F crystal according to claim 1, characterized in that: The frequency doubling device (2) is processed in the direction of the phase matching angle of the output laser, and the light-transmitting surface is polished.

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