193nm waveband ultraviolet laser generating device

Abstract

The invention discloses a device and a method for generating ultraviolet laser in a 193nm wave band. The device comprises a near-infrared laser driving unit 1, a nonlinear frequency conversion system 2 and an ultraviolet laser generating system 3 which are connected in sequence. The near-infrared laser driving unit is a high-power picosecond laser which generates near-infrared laser with the wavelength of 1064nm. The laser is changed into two parts after passing through a beam splitter, one part serves as pump light of a first optical parametric oscillator (OPO1) after frequency doubling, and the generated laser with the wavelength of 840 nm is changed into 210 nm after being subjected to quadruplicated frequency; and the other part is directly used as pump light of a second optical parametric oscillator (OPO2) to generate laser with the wavelength of 2380nm. And in the final ultraviolet laser generation system, the 210nm laser and the 2380nm laser are subjected to a sum frequency process to finally realize the output of the 193nm wave band ultraviolet laser. According to the invention, a mature nonlinear crystal and a nonlinear frequency conversion process are utilized, and a new thought and a technical route are provided for the development of a vacuum ultraviolet 193nm wave band solid laser.

Description

Technical Field

[0001] The invention belongs to the field of laser technology, and in particular relates to a device for generating ultraviolet laser in the 193nm band. Background Art

[0002] 193nm ultraviolet laser is an important tool for research in high-resolution spectroscopy, surface science, photochemistry, fiber grating preparation, integrated circuit etching, precision laser processing, etc. The development of 193nm ultraviolet laser is of great significance and has broad application prospects. At present, the main way to obtain 193nm ultraviolet laser is to rely on ArF excimer gas laser, which uses a combination of rare gas and reactive gas under high pressure to produce ultraviolet laser. However, it has the risk of harmful gases endangering personal safety and environmental pollution, as well as high cost, limited repetition frequency, poor beam quality, poor coherence and other disadvantages, which seriously limit the development of related research and application. Compared with gas lasers, solid 193nm laser has the advantages of adjustable repetition frequency, good beam quality, good coherence, small size, and tunable wavelength. With the continuous development of lasers, nonlinear crystals and related technologies, the advantages of using frequency doubling, sum frequency and other methods to generate 193nm ultraviolet laser through nonlinear frequency conversion are becoming more and more obvious compared to using gas lasers.

[0003] At present, the scheme based on nonlinear frequency conversion has been widely used in the generation of 193nm ultraviolet laser, but it has high requirements for the driving light source and related nonlinear crystals, and there are problems with low output power and conversion efficiency. In addition, the ultraviolet continuous laser generation system that combines fiber laser and diamond Raman technology uses diamond crystals to generate diamond Raman lasers, and further frequency conversion is performed on this basis to generate 193nm ultraviolet lasers. However, it has high requirements for the driving light source, and the diamond crystal needs to be specially cooled, which increases the complexity of the experiment.

[0004] Therefore, how to use a driving light source to stably and efficiently generate high-power 193nm band ultraviolet lasers, and to develop a variety of technical routes for generating 193nm band ultraviolet lasers are issues that researchers in this field urgently need to solve. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides a device and method for generating 193nm ultraviolet laser. The technical solutions of the present invention are as follows:

[0006] A device for generating ultraviolet laser in the 193nm band comprises a near-infrared laser driving unit, a nonlinear frequency conversion system and an ultraviolet laser generating system which are connected in sequence; wherein the near-infrared laser driving unit generates near-infrared laser with a wavelength of λ1; in the nonlinear frequency conversion system, the near-infrared laser with a wavelength of λ1 generated by the near-infrared driving unit is divided into two parts after passing through a beam splitter, wherein one part generates laser with a wavelength of λ2 through a frequency doubling process, λ2=λ1 / 2, then the laser with a wavelength of λ2 is used as pump light to pump a first optical parametric oscillator (OPO1) to generate laser with a wavelength of λ3, and then through a frequency quadrupling process to generate laser with a wavelength of λ4, λ4=λ3 / 4, and the other part directly pumps a second optical parametric oscillator (OPO2) to generate laser with a wavelength of λ5; then, two laser beams with wavelengths of λ4 and λ5 enter the ultraviolet laser generating system, and finally generate ultraviolet laser with a wavelength of λ6 in the 193nm band through a sum frequency method, 1 / λ6=1 / λ4+1 / λ5.

[0007] The near-infrared laser driving unit includes an optical fiber seed source, a stretcher, a pre-amplifier, a main amplifier, and a compressor;

[0008] The seed source is an optical fiber seed source, which generates a seed laser with a central wavelength of 1064nm and an energy of nanojoule level;

[0009] The stretcher is a CFBG stretcher, which is responsible for stretching the seed laser pulse width to hundreds of picoseconds or even nanoseconds;

[0010] The pre-amplifier is a regenerative amplifier, which has the advantages of good beam quality and simple structure;

[0011] The main amplifier is a dual-pass amplifier, which is responsible for further improving the laser energy output by the pre-amplifier;

[0012] The compressor uses a single grating compressor, which can provide negative second-order dispersion for the pulse, and is conjugate with the stretcher. The dispersion amount is adjusted by adjusting the incident angle and the delay position, and the amplified pulse is compressed to the picosecond level;

[0013] The nonlinear frequency conversion system includes a beam splitter, a first focusing system, a first nonlinear crystal, a first collimation system, a first optical parametric oscillator module, a second collimation system, a second focusing system, a third nonlinear crystal, a third collimation system, a third focusing system, a second optical parametric oscillator module and a fourth collimation system.

[0014] The first nonlinear crystal is used as a frequency doubling crystal to generate a frequency-doubled light with a wavelength of λ2 by single-pass frequency doubling, double-pass frequency doubling or cascaded single-pass frequency doubling, where λ2=λ1 / 2; the first optical parametric oscillator module uses the frequency-doubled light with a wavelength of λ2 generated by frequency doubling as pump light, and uses the second nonlinear crystal as a frequency conversion device to generate a signal light with a wavelength of λ3; the third nonlinear crystal is used as a quadruple frequency crystal, and uses the signal light with a wavelength of λ3 generated by the first optical parametric oscillator module as fundamental frequency light to generate a quadruple frequency light with a wavelength of λ4 by quadruple frequency doubling; the second optical parametric oscillator module uses a picosecond laser with a wavelength of λ1 output by a near-infrared laser driving unit as pump light, and uses the fourth nonlinear crystal as a frequency conversion device to generate an idler light with a wavelength of λ5.

[0015] The first nonlinear crystal refers to a single nonlinear crystal for realizing single-pass frequency doubling or double-pass frequency doubling, or a plurality of cascaded nonlinear crystals for realizing cascaded single-pass frequency doubling, such as β-barium metaborate crystal, lithium triborate crystal, bismuth triborate crystal, lithium cesium borate crystal, potassium titanyl phosphate crystal, potassium titanyl arsenate crystal, potassium dihydrogen phosphate crystal, potassium dideuterium phosphate crystal, diammonium dihydrogen phosphate crystal, dideuterium ammonium phosphate crystal, guanidine tetrafluoroborate crystal, yttrium calcium oxyborate crystal, periodically poled lithium niobate crystal, magnesium oxide-doped periodically poled lithium niobate crystal, periodically poled titanium oxide phosphate crystal. Potassium crystal or periodically poled potassium titanium arsenate crystal; the second nonlinear crystal refers to a nonlinear crystal used in the first optical parametric oscillator module to achieve frequency conversion from wavelength λ2 to λ3, such as lithium triborate crystal, barium borate crystal, bismuth borate crystal, etc.; the third nonlinear crystal refers to a nonlinear crystal used to achieve frequency quadrupling to achieve frequency conversion from wavelength λ3 to λ4, such as β-barium metaborate crystal; the fourth nonlinear crystal refers to a nonlinear crystal used in the second optical parametric oscillator module to achieve frequency conversion from wavelength λ1 to λ5, such as periodically poled magnesium oxide-doped lithium niobate crystal;

[0016] The ultraviolet laser generating system comprises a fourth focusing system, a fifth nonlinear crystal, and a fifth collimation system;

[0017] The fifth nonlinear crystal is used as a sum frequency crystal, and two light beams with wavelengths of λ4 and λ5 are used as fundamental frequency lights, and a sum frequency light with a wavelength of λ6 is generated by a sum frequency method.

[0018] The fifth nonlinear crystal refers to a nonlinear crystal used to achieve sum frequency, such as a lithium triborate crystal;

[0019] The first focusing system, the second focusing system, the third focusing system and the fourth focusing system, the first collimating system, the second collimating system, the third collimating system, the fourth collimating system and the fifth collimating system adopt a single lens or a lens group.

[0020] The near-infrared laser driving unit further includes a first spatial isolator and a second spatial isolator, wherein the first spatial isolator is connected between the stretcher and the pre-amplifier, and the second spatial isolator is connected between the pre-amplifier and the main amplifier.

[0021] Advantages of the present invention:

[0022] 1. The device and method for generating ultraviolet laser in the 193nm band of the present invention utilizes a picosecond laser generated by an ytterbium-doped picosecond solid laser as a driving light source, without the need for assistance from other lasers, thereby greatly simplifying the laser system.

[0023] 2. Compared with the existing ArF excimer gas laser, the present invention does not have the risk of endangering personal safety and environmental pollution, and has the advantages of scalable repetition frequency, good beam quality, good coherence, small size, adjustable pulse width, and tunable wavelength; compared with the diamond Raman laser, the crystals used for frequency conversion in the present invention are all very mature crystals, and have the characteristics of high efficiency, low cost, easy maintenance, and stable operation.

[0024] 3. The frequency conversion involved in the present invention is a nonlinear process with good flexibility, which can realize wavelength tunable output and provide convenience for generating high-power 193nm band ultraviolet laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a device and method system for generating 193nm ultraviolet laser in the present invention;

[0026] Figure 2 is a schematic structural diagram of a near-infrared drive unit included in the system of the present invention;

[0027] Figure 3 It is a structural schematic diagram of a nonlinear frequency conversion system included in the system of the present invention;

[0028] Figure 4 It is a schematic diagram of the structure of the ultraviolet laser generating system included in the system of the present invention;

[0029] Figure 5 is a schematic diagram of an optical path of a first optical parametric oscillator module included in the system of the present invention;

[0030] Figure 6 is a schematic diagram of an optical path of a second optical parametric oscillator module included in the system of the present invention;

[0031] In the accompanying drawings, a near-infrared laser driving unit 1, a seed source 11, a stretcher 12, a spatial isolator 13, a pre-amplifier 14, a spatial isolator 15, a main amplifier 16, a compressor 17, a nonlinear frequency conversion system 2, a beam splitter 21, a first focusing system 22, a first nonlinear crystal 23, a first collimation system 24, a first optical parametric oscillator module 25, a second collimation system 26, a second focusing system 27, a third nonlinear crystal 28, a third collimation system 29, and a third focusing system 210 are provided. , second optical parametric oscillator module 211, fourth collimation system 212, ultraviolet laser generating system 3, fourth focusing system 31, fifth nonlinear crystal 32, fifth collimation system 33, first dichroic mirror 251a, second dichroic mirror 251b, second nonlinear crystal 252, first end mirror 253, first coupling output mirror 254, third dichroic mirror 2111a, fourth dichroic mirror 2111b, fourth nonlinear crystal 2112, second end mirror 2113, second coupling output mirror 2114. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] The present invention provides a device and method for generating 193nm ultraviolet laser, such as Figure 1 The system shown includes: a near-infrared laser driving unit 1, a nonlinear frequency conversion system 2, and an ultraviolet laser generating system 3. The near-infrared laser driving unit 1 is used to generate a near-infrared laser with a wavelength of 1064nm as a system driving light source, the nonlinear frequency conversion system 2 obtains a laser of a desired wavelength band through nonlinear processes such as frequency doubling, optical parametric oscillation, and frequency quadrupling, and finally generates an ultraviolet laser of a wavelength band of 193nm through a sum frequency process in the ultraviolet laser generating system 3.

[0034] like Figure 2 As shown, the near-infrared laser driving unit 1 includes a seed source 11, a stretcher 12, a first spatial isolator 13, a pre-amplifier 14, a second spatial isolator 15, a main amplifier 16 and a compressor 17.

[0035] The seed source 11 is a Huari fiber seed source HR-Seed-ps, which can generate a seed laser with a central wavelength of 1064.3 nm and energy of nanojoule level.

[0036] The stretcher 12 is a CFBG stretcher PWS-HPSR manufactured by Teraxion, which is responsible for stretching the seed laser pulse width to hundreds of picoseconds or even nanoseconds.

[0037] The pre-amplifier 14 is a regenerative amplifier, which has the advantages of good beam quality and simple structure.

[0038] The main amplifier 16 is a dual-pass amplifier, which is responsible for further increasing the laser energy output by the pre-amplifier.

[0039] The first space isolator 13 and the second space isolator 15 are both used to prevent the reflected light from damaging the front-stage optical elements and equipment.

[0040] The compressor 17 uses a single grating compressor, which can provide negative second-order dispersion for the pulse, and is conjugate with the stretcher. The dispersion amount is adjusted by adjusting the incident angle and the delay position, and the amplified pulse is compressed to the picosecond level.

[0041] like Figure 3 , Figure 5 and Figure 6 As shown, the nonlinear frequency conversion system 2 includes a beam splitter 21, a first focusing system 22, a first nonlinear crystal 23, a first collimation system 24, a first optical parametric oscillator module 25, a second collimation system 26, a second focusing system 27, a third nonlinear crystal 28, a third collimation system 29, a third focusing system 210, a second optical parametric oscillator module 211, a fourth collimation system 212, a first dichroic mirror 251a, a second dichroic mirror 251b, a second nonlinear crystal 252, a first end mirror 253, a first coupling output mirror 254, a third dichroic mirror 2111a, a fourth dichroic mirror 2111b, a fourth nonlinear crystal 2112, a second end mirror 2113, and a second coupling output mirror 2114.

[0042] The first nonlinear crystal 23 is used as a frequency doubling crystal to generate a frequency-doubled light with a wavelength of λ2 by single-pass frequency doubling, double-pass frequency doubling or cascaded single-pass frequency doubling, where λ2=λ1 / 2; the first optical parametric oscillator module 25 uses the frequency-doubled light with a wavelength of λ2 as pump light, which enters the first optical parametric oscillator module through the first dichroic mirror 251a, and uses the second nonlinear crystal 252 as a frequency conversion device to generate a signal light with a wavelength of λ3, which oscillates in a resonant cavity composed of the first dichroic mirror 251a, the second dichroic mirror 251b, the first end mirror 253 and the first coupling output mirror 254, and is finally output through the first coupling output mirror 254; the third nonlinear crystal 28 is used as a quadruple A frequency crystal is used, and the signal light with a wavelength of λ3 generated by the first optical parametric oscillator module is used as the fundamental frequency light, and a quadrupled frequency light with a wavelength of λ4 is generated by quadrupling the frequency; the second optical parametric oscillator module 211 uses the picosecond laser with a wavelength of λ1 output by the near-infrared laser driving unit as the pump light, and the pump light enters the second optical parametric oscillator module through the third dichroic mirror 2111a, and uses the fourth nonlinear crystal 2112 as a frequency conversion device to generate an idler light with a wavelength of λ5, which oscillates in the resonant cavity composed of the third dichroic mirror 2111a, the fourth dichroic mirror 2111b, the second end mirror 2113, and the second coupling output mirror 2114, and is finally output through the second coupling output mirror 2114;

[0043] The first nonlinear crystal refers to a single nonlinear crystal used to achieve single-pass frequency doubling or double-pass frequency doubling, or multiple cascaded nonlinear crystals used to achieve cascaded single-pass frequency doubling, and is selected from β-barium metaborate crystals, lithium triborate crystals, bismuth triborate crystals, lithium cesium borate crystals, potassium titanyl phosphate crystals, potassium titanyl arsenate crystals, potassium dihydrogen phosphate crystals, potassium deuterium phosphate crystals, diammonium dihydrogen phosphate crystals, diammonium deuterium phosphate crystals, guanidine tetrafluoroborate crystals, yttrium calcium oxidoborate crystals, periodically poled lithium niobate crystals, magnesium oxide-doped periodically poled lithium niobate crystals, periodically poled potassium titanyl phosphate crystals or periodically poled potassium titanyl arsenate crystals.

[0044] The second nonlinear crystal refers to a nonlinear crystal used in the first optical parametric oscillator module to achieve frequency conversion from wavelength λ2 to λ3, and lithium triborate crystal, barium borate crystal, and bismuth borate crystal are selected.

[0045] The third nonlinear crystal refers to a nonlinear crystal used to realize frequency quadrupling, realizing frequency conversion from wavelength λ3 to λ4, and β-barium borate crystal is selected.

[0046] The fourth nonlinear crystal refers to a nonlinear crystal used in the second optical parametric oscillator module to achieve frequency conversion from wavelength λ1 to λ5, and is a periodically polarized magnesium oxide-doped lithium niobate crystal.

[0047] The first dichroic mirror and the second dichroic mirror refer to lenses having high transmittance for lasers with a wavelength of λ2 band and high reflectivity for lasers with a wavelength of λ3 band; the third dichroic mirror and the fourth dichroic mirror refer to lenses having high transmittance for lasers with a wavelength of λ1 band and high reflectivity for lasers with a wavelength of λ5 band.

[0048] The first end mirror refers to a lens having high reflectivity for lasers with wavelengths in the λ2 and λ3 bands; the second end mirror refers to a lens having high reflectivity for lasers with wavelengths in the λ1 and λ5 bands.

[0049] The first coupling output mirror refers to a lens having high reflectivity for lasers with a wavelength of λ2 band and a certain transmittance for lasers with a wavelength of λ3 band; the second coupling output mirror refers to a lens having high reflectivity for lasers with a wavelength of λ1 band and a certain transmittance for lasers with a wavelength of λ5 band.

[0050] like Figure 4 As shown, the ultraviolet laser generating system 3 includes a fourth focusing system 31, a fifth nonlinear crystal 32 and a fifth collimating system 33 which are connected in sequence.

[0051] The five nonlinear crystals 32 are used as sum frequency crystals, and two light beams with wavelengths of λ4 and λ5 are used as fundamental frequency lights to generate sum frequency light with a wavelength of λ6 through sum frequency method.

[0052] The fifth nonlinear crystal refers to a nonlinear crystal used to realize the sum frequency generation of a sum frequency light with a wavelength of λ6 by using two light beams with wavelengths of λ4 and λ5, and a lithium triborate crystal is selected.

[0053] The first focusing system 22, the second focusing system 27, the third focusing system 210 and the fourth focusing system 31, the first collimating system 24, the second collimating system 26, the third collimating system 29, the fourth collimating system 212 and the fifth collimating system 33 may all adopt a single lens or a lens group.

[0054] Example

[0055] The high-power near-infrared laser with a wavelength of 1064nm generated by the near-infrared laser driving unit 1 enters the nonlinear frequency conversion system 2, and is divided into two parts after passing through the beam splitter 21. One part passes through the first focusing system 22, enters the β-barium metaborate crystal, and generates a doubled frequency light with a wavelength of 532nm after frequency conversion, and then enters the first optical parametric oscillator module, and generates a signal light with a wavelength of 840nm after frequency conversion through the lithium triborate crystal therein, and then passes through the second focusing system 27, enters the β-barium metaborate crystal, and generates a quadrupled frequency light with a wavelength of 210nm after frequency conversion; the other part enters the second optical parametric oscillator module, and generates an idler light with a wavelength of 2380nm after frequency conversion through the periodically polarized magnesium oxide-doped lithium niobate crystal therein. The quadrupled frequency light with a wavelength of 210nm and the idler light with a wavelength of 2380nm enter the ultraviolet laser generation system 3 together, and enter the lithium triborate crystal after passing through the fourth focusing system 31, and generate an ultraviolet laser with a wavelength of 193nm after frequency conversion.

[0056] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A 193nm band ultraviolet laser generating device, characterized in that: The invention comprises a near-infrared laser driving unit, a nonlinear frequency conversion system and an ultraviolet laser generating system which are connected in sequence. The near-infrared laser driving unit generates a near-infrared laser with a wavelength of λ1, where λ1 is 1064nm. The nonlinear frequency conversion system divides the near-infrared laser into two paths through a beam splitter, wherein one path generates a visible laser with a wavelength of λ2 for pumping a first optical parametric oscillator (OPO1) through a frequency doubling process to generate a laser with a wavelength of λ3, and then generates a laser with a wavelength of λ4 through a frequency quadrupling process. The other path directly pumps a second optical parametric oscillator (OPO2) through the near-infrared laser to generate a laser with a wavelength of λ5. The ultraviolet laser generating system generates an ultraviolet laser with a wavelength of λ6 in the 193nm band by summing the two laser beams with wavelengths of λ4 and λ5 through a sum frequency method.

2. A 193nm band ultraviolet laser generating device according to claim 1, characterized in that: The near-infrared laser driving unit includes an optical fiber seed source, a stretcher, a pre-amplifier, a main amplifier, and a compressor; the optical fiber seed source generates seed light with a central wavelength of 1064nm, which is stretched by the stretcher, then enters the pre-amplifier and the main amplifier in sequence for amplification, and finally is compressed by the compressor to obtain a high-power near-infrared picosecond laser output.

3. A 193nm band ultraviolet laser generating device according to claim 2, characterized in that: The seed source is a commercial optical fiber seed source, which generates seed light with a central wavelength of 1064nm and energy in the nanojoule level. The stretcher is a chirped fiber grating (CFBG) stretcher. The pre-amplifier is a regenerative amplifier. The main amplifier is a dual-pass amplifier. The compressor is a single grating compressor.

4. The 193nm band ultraviolet laser generating device according to claim 2, characterized in that: A first spatial isolator is connected between the stretcher and the pre-amplifier, and a second spatial isolator is connected between the pre-amplifier and the main amplifier.

5. The 193nm band ultraviolet laser generating device according to claim 1, characterized in that: The nonlinear frequency conversion includes a beam splitter and two optical paths through which the near-infrared laser generated by the near-infrared laser driving unit is split, one optical path sequentially passing through a first focusing system, a first nonlinear crystal, a first collimation system, a first optical parametric oscillator module, a second collimation system, a second focusing system, a third nonlinear crystal, and a third collimation system, and the other optical path sequentially passing through a third focusing system, a second optical parametric oscillator module, and a fourth collimation system; The first nonlinear crystal is used as a frequency doubling crystal to generate a frequency-doubled light with a wavelength of λ2 by single-pass frequency doubling, double-pass frequency doubling or cascaded single-pass frequency doubling, where λ2=λ1 / 2; the first optical parametric oscillator module uses the frequency-doubled light with a wavelength of λ2 as pump light and uses the second nonlinear crystal as a frequency conversion device to generate a signal light with a wavelength of λ3; the third nonlinear crystal is used as a quadruple frequency crystal to use the signal light with a wavelength of λ3 generated by the first optical parametric oscillator module as fundamental frequency light to generate a quadruple frequency light with a wavelength of λ4 by quadruple frequency doubling; the second optical parametric oscillator module uses a picosecond laser with a wavelength of λ1 output by a near-infrared laser driving unit as pump light and uses the fourth nonlinear crystal as a frequency conversion device to generate an idler light with a wavelength of λ5.

6. The 193nm band ultraviolet laser generating device according to claim 5, characterized in that: The beam splitter is a non-polarizing beam splitter; the first nonlinear crystal is a β-barium metaborate crystal, a lithium triborate crystal, a bismuth triborate crystal, a lithium cesium borate crystal, a potassium titanyl phosphate crystal, a potassium titanyl arsenate crystal, a potassium dihydrogen phosphate crystal, a potassium dideuterium phosphate crystal, a diammonium dihydrogen phosphate crystal, a dideuterium ammonium phosphate crystal, a guanidine tetrafluoroborate crystal, a calcium yttrium oxide borate crystal, a periodically poled lithium niobate crystal, a magnesium oxide-doped periodically poled lithium niobate crystal, a periodically poled potassium titanyl phosphate crystal or a periodically poled potassium titanyl arsenate crystal; the second nonlinear crystal is a lithium triborate crystal, a barium borate crystal or a bismuth borate crystal; the third nonlinear crystal is a β-barium metaborate crystal; the fourth nonlinear crystal is a periodically poled magnesium oxide-doped lithium niobate crystal.

7. The 193nm band ultraviolet laser generating device according to claim 5, characterized in that: The first focusing system, the second focusing system, the third focusing system, the first collimating system, the second collimating system, the third collimating system and the fourth collimating system are a single lens or a lens group.

8. The 193nm band ultraviolet laser generating device according to claim 1, characterized in that: The ultraviolet laser generating system comprises a fourth focusing system, a fifth nonlinear crystal and a fifth collimating system. The two laser beams generated by the nonlinear frequency conversion system are focused by the fourth focusing system, and then the two laser beams are frequency-added by the fifth nonlinear crystal, and then collimated and output by the fifth collimating system.

9. The 193nm band ultraviolet laser generating device according to claim 8, characterized in that: The fifth nonlinear crystal is a sum frequency crystal and is a lithium triborate crystal.

10. The 193nm band ultraviolet laser generating device according to claim 8, characterized in that: The fourth focusing system and the fifth collimating system are a single lens or a lens group.

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