All-solid-state continuous-wave vacuum ultraviolet laser using a double-resonant cavity

Abstract

The present invention relates to the technical field of lasers, and particularly relates to an all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity. A first cavity mirror M1, a first laser crystal C1, a fourth cavity mirror M4, a fifth cavity mirror M5, and a sixth cavity mirror M6 form a first laser resonant cavity; a second cavity mirror M2, a second laser crystal C2, a third cavity mirror M3, the fourth cavity mirror M4, the fifth cavity mirror M5, and the sixth cavity mirror M6 form a second laser resonant cavity; a first nonlinear optical crystal O1 is disposed between the fifth cavity mirror M5 and the sixth cavity mirror M6 to frequency-double the 526-nm laser generated by the first resonant cavity into a 263-nm frequency-doubled laser; a second nonlinear optical crystal O2 is disposed between the fourth cavity mirror M4 and the fifth cavity mirror M5 to sum-frequency the 725-nm fundamental-frequency laser generated by the second resonant cavity and the 263-nm frequency-doubled laser generated by the first nonlinear optical crystal O1 to generate a 193-nm vacuum ultraviolet laser, which is output through the fourth cavity mirror M4. The present invention has a simple internal structure and requires fewer frequency conversion times.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, and more particularly to a all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity. Background Art

[0002] Vacuum ultraviolet laser refers to a laser light source with a wavelength in the range of 100-200 nm. Among them, 193 nm is a very important wavelength and is an important tool for high-resolution spectroscopy, photochemistry, fiber grating fabrication, integrated circuit etching, precision laser processing, etc. Especially in the field of semiconductor integrated circuit manufacturing, with the increasing chip integration and the continuous reduction of the scribing scale, the wavelength of the required lithography light source is getting shorter and shorter.

[0003] Currently, the ArF excimer gas laser is the only type of laser light source that can directly generate laser output at the vacuum ultraviolet wavelength of 193 nm. It usually generates ultraviolet laser by using a combination of rare gases and reactive gases under high pressure, has a relatively large output power, and occupies a large market share of the lithography light source. However, the working medium of the ArF excimer laser contains fluorine gas, which is toxic and corrosive, and there are risks of harming personal safety and environmental pollution; in addition, the pulsed repetition frequency of the gas laser is limited (usually <10 kHz), the peak power is relatively high, the beam quality is poor, and the coherence is poor, which limits its application in detection.

[0004] Compared with gas lasers, solid 193 nm laser light sources have the advantages of high repetition frequency, good beam quality, good coherence, small volume, adjustable pulse width, etc. The generation process of this type of solid light source mainly relies on nonlinear optical frequency conversion. Although the output power and efficiency are relatively low, it can already meet the requirements of applications such as fiber grating writing, angle-resolved photoemission spectroscopy experiments, semiconductor chip defect detection, and ArF excimer gas laser seed injection.

[0005] For a solid-state 193 nm laser source, the selection of the fundamental frequency source and the choice of the nonlinear optical frequency conversion path are crucial, directly determining the efficiency and complexity of the entire laser system. Currently, solid-state 193 nm lasers generally use near-infrared lasers as the fundamental frequency source and obtain 193 nm laser output through more than 3 times of intracavity or extracavity frequency conversion. For example, in the paper "Advanced Photonics Nexus, 3, 026012, 2024", 258 nm laser is first obtained through the second harmonic generation of a 1030 nm light source, and then 193 nm output is achieved through the second sum frequency with a 1553 nm light source, experiencing a total of 4 times of frequency conversion. In the paper "Optics Letters, 40, 5590 - 5593, 2015", 275.5 nm laser is first obtained through the second harmonic generation of an 1102 nm light source, then 234.1 nm laser is obtained through the sum frequency with a 1560 nm light source, and finally 193.4 nm output is achieved through the sum frequency with an 1110 nm light source, also experiencing 4 times of frequency conversion. And 3 kinds of fundamental frequency light sources (1102 nm, 1560 nm, 1110 nm) are used. In the patent document CN118610880 A, the 773.6 nm laser of a emerald crystal is used as the fundamental frequency source, and frequency doubling, tripling, and quadrupling are carried out with a nonlinear crystal for a total of 3 times of frequency conversion to achieve the output of the target wavelength of 193.4 nm. To sum up, the existing solid-state 193 nm laser technologies all use 3 times or more of nonlinear optical frequency conversion, having disadvantages such as complex generation processes, serious energy attenuation, low conversion efficiency, high manufacturing costs, and poor reliability.

[0006] Therefore, how to provide a 193 nm ultraviolet laser with a simple structure and few frequency conversion times has become a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides a all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity, which has a simple internal structure and few frequency conversion times.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity, comprising: a first pump source LD1, a first cavity mirror M1, a first laser crystal C1, a second cavity mirror M2, a second laser crystal C2, a third cavity mirror M3, a fourth cavity mirror M4, a fifth cavity mirror M5, a sixth cavity mirror M6, a first nonlinear optical crystal O1, and a second nonlinear optical crystal O2;

[0010] Wherein, the first cavity mirror M1, the first laser crystal C1, the fourth cavity mirror M4, the fifth cavity mirror M5, and the sixth cavity mirror M6 form a first laser resonant cavity;

[0011] The second endoscope M2, the second laser crystal C2, the third endoscope M3, the fourth endoscope M4, the fifth endoscope M5 and the sixth endoscope M6 form a second laser resonator;

[0012] The first nonlinear optical crystal O1 is disposed between the fifth endoscope M5 and the sixth endoscope M6, and doubles the 526 nm laser generated by the first resonator into a second harmonic laser of 263 nm;

[0013] The second nonlinear optical crystal O2 is disposed between the fourth endoscope M4 and the fifth endoscope M5, and sum - frequency mixes the 725 nm fundamental frequency laser generated by the second resonator and the 263 nm second harmonic laser generated by the first nonlinear optical crystal O1 to generate a vacuum ultraviolet laser of 193 nm ± 2 nm, which is output through the fourth endoscope M4.

[0014] Further, a first birefringent filter BRF1 (Birefringence Filter) is inserted into the optical cavity formed by the first endoscope M1 and the third endoscope M3; a second birefringent filter BRF2 is inserted into the optical cavity formed by the second endoscope M2 and the third endoscope M3.

[0015] Further, the first birefringent filter BRF1 and the second birefringent filter BRF2 are both made of quartz, with a thickness of 0.5 mm, and the optical axis C is parallel to the surface;

[0016] The first birefringent filter BRF1 is inserted into the optical cavity formed by the first endoscope M1 and the third endoscope M3 at a Brewster angle of 57.28°, adjusts the angle A between the incident plane and the principal plane to 38.1°, and controls the laser wavelength at 526 nm;

[0017] The second birefringent filter BRF2 is inserted into the optical cavity formed by the second endoscope M2 and the third endoscope M3 at a Brewster angle of 57.15°, adjusts the angle α between the incident plane and the principal plane to 38.8°, and controls the laser wavelength at 725 nm.

[0018] Further, both the first laser crystal C1 and the second laser crystal C2 are Pr 3+ :SRA, Pr 3+ :YLF or Pr 3+ :LMA; wherein, both end - faces of the first laser crystal C1 are coated with an antireflection film at 526 nm; both end - faces of the second laser crystal C2 are coated with an antireflection film at 725 nm.

[0019] Further, the first nonlinear optical crystal O1 is a frequency doubling crystal for 526 nm laser, and is made of β-BBO crystal, KDP crystal or ADP crystal, and antireflection films of 725 nm, 526 nm and 263 nm are coated on its two light-passing end faces.

[0020] Further, the second nonlinear optical crystal O2 is a sum frequency crystal for 725 nm laser and 263 nm laser, and is made of β-BBO crystal or KBBF crystal, and antireflection films of 725 nm, 526 nm, 263 nm and 193 nm are coated on its two light-passing end faces.

[0021] Further, both the first pump source LD1 and the second pump source LD2 are laser diodes with spatial output or fiber-coupled output, and the laser wavelength they emit is 445 nm.

[0022] Further, the first cavity mirror M1 is a plane mirror coated with a dielectric film with 445 nm antireflection and 526 nm high reflection, and is arranged close to the first pump source LD1; the second cavity mirror M2 is a plane mirror coated with a dielectric film with 445 nm high transmission and 725 nm high reflection, and is arranged close to the second pump source LD2;

[0023] The first laser crystal C1 is located between the first cavity mirror M1 and the second cavity mirror M2, and is arranged close to the first cavity mirror M1; the second laser crystal C2 is located between the second cavity mirror M2 and the third cavity mirror M3, and is arranged close to the second cavity mirror M2.

[0024] Further, the third cavity mirror M3 is arranged between the first cavity mirror M1 and the fourth cavity mirror M4, and is placed at an angle of 45 degrees relative to the optical path M1M4;

[0025] The third cavity mirror M3 is a plane mirror coated with a dielectric film with 526 nm high transmission and 725 nm high reflection, and is used to separate the first laser resonator and the second laser resonator.

[0026] Further, the fourth cavity mirror M4 is a plano-concave mirror, serving as a common reflection cavity mirror for the first laser resonator and the second laser resonator, and an output mirror for 193 nm laser; on the side of the fourth cavity mirror M4 close to the resonator, a dielectric film with 193 nm high transmission, 526 nm high reflection and 725 nm high reflection is coated, and on the side far from the resonator, a dielectric film with 193 nm high transmission is coated;

[0027] The fifth cavity mirror M5 is a plano-concave mirror, serving as a common reflection cavity mirror for the first laser resonator and the second laser resonator; on the side of the fifth cavity mirror M5 close to the resonator, a dielectric film with 263 nm high reflection, 526 nm high reflection and 725 nm high reflection is coated;

[0028] The sixth mirror M6 is a plane mirror and serves as a common reflecting mirror for the first laser resonator and the second laser resonator; a dielectric film with high reflectivity at 263 nm, high reflectivity at 526 nm, high transmittance at 600 - 650 nm, and high reflectivity at 725 nm is coated on the side of the sixth mirror M6 close to the resonator;

[0029] The first nonlinear optical crystal O1 is arranged close to the sixth mirror M6; the second nonlinear optical frequency crystal O2 is arranged at the waist of the optical cavity formed by the fourth mirror M4 and the fifth mirror M5.

[0030] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The fundamental optical frequencies used in the present invention are 526 nm and 725 nm. Only two - stage frequency conversion is required to obtain 193 - nm laser output. Compared with the previous three - to - five - stage frequency conversion, the nonlinear optical conversion process is less, and the overall conversion efficiency is higher.

[0032] 2. The first laser resonator and the second laser resonator of the present invention share mirrors M3, M4, and M5, and the two resonators are separated by mirror M3. The two resonators form a multi - mirror folded cavity. A total of four waist positions are designed in the two resonators, and the laser crystals C1, C2 and the nonlinear optical crystals O1, O2 are placed respectively, ensuring high power and high efficiency of continuous laser generation and nonlinear frequency - conversion output.

[0033] 3. The present invention uses birefringent filters to regulate the laser wavelengths of the two resonators respectively, accurately controls the oscillating laser wavelengths at 526 nm and 725 nm, with narrow spectral lines and stable output. At the same time, the BRF also enables the output wavelength of this laser to have a certain tunability near 193 nm, which can meet various special requirements, such as accurate alignment with the wavelength when used as a seed source for ArF excimer gas laser.

[0034] 4. The present invention carefully selects rare - earth ions and host crystals, and determines Pr 3+ :SRA crystal as the working medium for generating 193 - nm solid - state laser. The center wavelength of the P1→ 3 H5 radiative transition of this crystal is at 525 nm, and the radiative bandwidth is 9.8 nm. It is easy to obtain 526 - nm laser through the frequency selection of BRF. Its 3 P0→ 3 F4 radiative transition center wavelength is at 725 nm, and the radiative bandwidth is 4.35 nm. It is easy to lock the output laser at 725 nm through the use of BRF. Therefore, Pr 3 F4 radiative transition center wavelength is at 725 nm, and the radiative bandwidth is 4.35 nm. It is easy to lock the output laser at 725 nm through the use of BRF. Therefore, Pr 3+: The efficient emission of the SRA crystal at 526 nm and 725 nm ensures that the output of vacuum ultraviolet laser with an accurate wavelength of 193 nm can be achieved through further intracavity frequency conversion. Moreover, the characteristic of its relatively large fluorescence emission bandwidth also endows the laser with a certain wavelength tuning ability near 193 nm, which can be adjusted according to actual needs, only by slightly adjusting the BRF and the nonlinear optical crystal.

[0035] In summary, the present invention reduces the frequency conversion steps for generating 193 nm solid-state laser, improves the conversion efficiency, reduces the device volume, simplifies the internal structure, and has the advantages of wavelength tunability, good reliability, easy maintenance, and low cost. Brief Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0037] Figure 1 It is a schematic structural diagram of a fully solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity provided in Embodiment 1 of the present invention.

[0038] Figure 2 It is a schematic optical path diagram of the fundamental frequency laser passing through the birefringent filter in Embodiment 1 of the present invention.

[0039] Figure 3 It is a schematic diagram of the transmission characteristic (α = 38.1°, d = 0.5 mm) of the first birefringent filter BRF1 in Embodiment 1 of the present invention.

[0040] Figure 4 It is a schematic diagram of the transmission characteristic (α = 38.8°, d = 0.5 mm) of the second birefringent filter BRF2 in Embodiment 1 of the present invention.

[0041] Figure 5 It is a schematic diagram of the beam size at each position within the first laser resonant cavity surrounded by M1 - M4 - M5 - M6 in Embodiment 1 of the present invention.

[0042] Figure 6 It is a schematic diagram of the beam size at each position within the second laser resonant cavity surrounded by M2 - M3 - M4 - M5 - M6 in Embodiment 1 of the present invention. Detailed Embodiments

[0043] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] Embodiment 1: The output wavelength of the vacuum ultraviolet laser in this embodiment is 193 nm, and the specific structure is as Figure 1 shown, including: the first pump source LD1, the first cavity mirror M1, the first laser crystal C1, the second cavity mirror M2, the second laser crystal C2, the third cavity mirror M3, the fourth cavity mirror M4, the fifth cavity mirror M5, the sixth cavity mirror M6, the first nonlinear optical crystal O1, and the second nonlinear optical crystal O2;

[0045] Among them, the first cavity mirror M1, the first laser crystal C1, the fourth cavity mirror M4, the fifth cavity mirror M5, and the sixth cavity mirror M6 form the first laser resonator;

[0046] The second cavity mirror M2, the second laser crystal C2, the third cavity mirror M3, the fourth cavity mirror M4, the fifth cavity mirror M5, and the sixth cavity mirror M6 form the second laser resonator;

[0047] A first birefringent filter BRF1 is inserted into the optical cavity M1M3 formed by the first cavity mirror M1 and the third cavity mirror M3; a second birefringent filter BRF2 is inserted into the optical cavity M2M3 formed by the second cavity mirror M2 and the third cavity mirror M3; the two birefringent filters are used to accurately adjust the oscillation wavelength to 526 nm and 725 nm.

[0048] The first nonlinear optical crystal O1 is arranged between the fifth cavity mirror M5 and the sixth cavity mirror M6 to double - frequency the 526 - nm laser generated by the first resonator into a second - harmonic laser of 263 nm;

[0049] The second nonlinear optical crystal O2 is arranged between the fourth cavity mirror M4 and the fifth cavity mirror M5 to perform sum - frequency mixing on the 725 - nm fundamental - frequency laser generated by the second resonator and the 263 - nm second - harmonic laser generated by the first nonlinear optical crystal O1 to generate a 193 - nm vacuum ultraviolet laser, which is output through the fourth cavity mirror M4.

[0050] To ensure the effective convergence of the pump light, a focusing lens F1 is arranged between the first pump source LD1 and the first mirror cavity M1, and a focusing lens F2 is arranged between the second pump source LD2 and the second mirror cavity M2. The focal lengths of F1 and F2 are both 100 mm, and their function is to focus the pump light emitted by LD1 and LD2 onto the laser crystals C1 and C2.

[0051] Specifically, the first birefringent filter BRF1 is made of quartz, with a thickness of 0.5 mm, and its optical axis C is parallel to the surface. The first birefringent filter BRF1 is inserted into the optical cavity M1M3 formed by the first mirror M1 and the third mirror M3 at the Brewster angle of 57.28° (corresponding to 526 nm), and the angle A between the incident plane (the plane formed by the incident light and the normal of the birefringent filter plane) and the principal plane (the plane formed by the normal of the birefringent filter plane and the optical axis) is adjusted to 38.1° to accurately control the oscillation wavelength at 526 nm. The optimization process of the above parameters is as follows:

[0052] Insert the first birefringent filter BRF1 at the Brewster angle θ b into the laser resonator, and the propagation optical path of the fundamental frequency laser is as Figure 2 shown. Due to the birefringence effect, a certain phase difference will be generated between the incident o-ray and e-ray after passing through the BRF:

[0053]

[0054] where λ is the incident wavelength, n o and n e are the refractive indices of the ordinary light and extraordinary light respectively, d is the thickness of the BRF, and β is the angle between the optical axis and the wave vector of the ordinary light wave. The angle between the incident plane (the plane formed by the incident light and the normal of the birefringent filter plane) and the principal plane (the plane formed by the normal of the birefringent filter plane and the optical axis) is the tuning angle α, and there is the following geometric relationship:

[0055] cosβ = cosαcosθ b (2)

[0056] The o-ray and e-ray passing through the first birefringent filter BRF1 will interfere when they exit from the rear surface, and the single-pass transmittance of BRF1 can be calculated from the interference light intensity. When the polarized light is incident at the Brewster angle, the transmittance can be expressed as:

[0057]

[0058] where φ represents the angle between the o-ray and the electric displacement vector of the incident light, and there is:

[0059] sinφ = cotβ·tnaθ b (4)

[0060] According to the above formula, the tuning effect of BRF1 on the laser wavelength after being inserted into the resonator can be theoretically simulated. Take the Brewster angle as 57.28°, and the birefringence Δn = n e -n oIt is approximately 0.009. By taking different thicknesses d and tuning angles α, the following conclusions can be obtained from the calculation results of formula (3): at the same tuning angle α, the greater the thickness of the BRF, the narrower the main peak of its transmittance will be compressed. As the thickness of BRF1 increases, the interval between the transmittance peaks becomes smaller and smaller, and in this case, multi-wavelength output may occur within the gain range of the laser crystal. In order to minimize the insertion loss of BRF1 while considering its mechanical strength, the thickness d of BRF1 is optimized to 0.5 mm. When the tuning angle α is near 40°, the minimum transmittance of the wavelength is almost zero, and the linewidth compression effect is the best. The more the tuning angle α deviates from 40°, the higher the minimum transmittance and the worse the linewidth narrowing effect. Through multiple iterative optimizations, when d = 0.5 mm, the corresponding α = 38.1° for the transmittance of 1 at 526 nm, and its transmittance curve is as shown in Figure 3 shown.

[0061] Similarly, the optimized parameters of the second birefringent filter BRF2 can be obtained. The second birefringent filter BRF2 is inserted into the optical cavity M2M3 formed by the second mirror M2 and the third mirror M3 at the Brewster angle of 57.15°. The angle α between the incident plane (the plane formed by the incident light and the normal of the birefringent filter plane) and the principal plane (the plane formed by the normal of the birefringent filter plane and the optical axis) is adjusted to 38.8°, and the oscillating laser wavelength is accurately controlled at 725 nm. Its transmittance curve is as shown in the appendix Figure 4 shown.

[0062] The first laser crystal C1 and the second laser crystal C2 are both Pr 3+ :SRA(Pr 3+ :SrAl 12 O 19 ), with a doping concentration of 0.5 at.%. Among them, the two light-passing end faces of the first laser crystal C1 are coated with an antireflection film at 526 nm and emit 526 nm laser under the feedback of the 526 nm laser resonator. The two light-passing end faces of the second laser crystal C2 are coated with an antireflection film at 725 nm and emit 725 nm laser under the feedback of the 725 nm laser resonator.

[0063] The first nonlinear optical crystal O1 is the frequency-doubling crystal of the 526 nm laser. Its two light-passing end faces are coated with antireflection films at 725 nm, 526 nm, and 263 nm, and generate 263 nm frequency-doubled laser through type-I phase matching. When O1 is a β-BBO crystal, the processing angles are (θ = 48.5°, φ = 0°). When O1 is a CLBO crystal, the processing angles are (θ = 62.8°, φ = 45°). When C3 is a KDP crystal, the processing angles are (θ = 79.5°, φ = 45°). When O1 is an ADP crystal, the processing angles are (θ = 83.7°, φ = 45°).

[0064] The second nonlinear optical crystal O2 is a sum-frequency crystal for 725 nm laser and 263 nm laser, using β-BBO crystal or KBBF crystal, and its two light-passing end faces are coated with antireflection films of 725 nm, 526 nm, 263 nm and 193 nm, and generate 193 nm frequency-doubled laser through type-I phase matching. When O2 is a β-BBO crystal, the processing angle is (θ = 74.8°, φ = 0°). When O2 is a KBBF crystal, the processing angle is (θ = 47.1°, φ = 0°).

[0065] Both the first pump source LD1 and the second pump source LD2 are laser diodes (LD, laser diode) with spatial output or fiber-coupled output, the central wavelength is 445 nm, and it is aligned with Pr 3+ : the 3 H4→ 3 Absorption peak of the P2 energy level transition.

[0066] The first cavity mirror M1 is a plane mirror, coated with a dielectric film with 445 nm antireflection and 526 nm high reflection, and is arranged close to the first pump source LD1; the second cavity mirror M2 is a plane mirror, coated with a dielectric film with 445 nm high transmission and 725 nm high reflection, and is arranged close to the second pump source LD2; the first laser crystal C1 is located between the first cavity mirror M1 and the second cavity mirror M2, and is arranged close to the first cavity mirror M1; the second laser crystal C2 is located between the second cavity mirror M2 and the third cavity mirror M3, and is arranged close to the second cavity mirror M2.

[0067] The third cavity mirror M3 is arranged between the first cavity mirror M1 and the fourth cavity mirror M4, and is placed at an angle of 45 degrees relative to the optical path M1M4;

[0068] The third cavity mirror M3 is a plane mirror, coated with a dielectric film with 526 nm high transmission and 725 nm high reflection, and is used to separate the first laser resonator and the second laser resonator.

[0069] The fourth cavity mirror M4 is a plano-concave mirror, serving as the common reflection mirror of the first laser resonator and the second laser resonator, and the output mirror of 193 nm laser; the side of the fourth cavity mirror M4 close to the resonator is coated with a dielectric film with 193 nm high transmission, 526 nm high reflection and 725 nm high reflection, and the side far from the resonator is coated with a 193 nm high transmission dielectric film.

[0070] The fifth cavity mirror M5 is a plano-concave mirror, serving as the common reflection mirror of the first laser resonator and the second laser resonator; the side of the fifth cavity mirror M5 close to the resonator is coated with a dielectric film with 263 nm high reflection, 526 nm high reflection and 725 nm high reflection.

[0071] The sixth cavity mirror M6 is a plane mirror and serves as the common reflecting cavity mirror for the first laser resonator and the second laser resonator; on the side of the sixth cavity mirror M6 close to the resonator, a dielectric film with high reflectivity at 263 nm, high reflectivity at 526 nm, high transmittance at 600 - 650 nm, and high reflectivity at 725 nm is coated.

[0072] The first laser crystal C1 is arranged close to the first cavity mirror M1, and the second laser crystal C2 is arranged close to the second cavity mirror M2. The first nonlinear optical crystal O1 is arranged close to the sixth cavity mirror M6; the second nonlinear optical frequency crystal O2 is arranged at the waist of the optical cavity formed by the fourth cavity mirror M4 and the fifth cavity mirror M5.

[0073] In this embodiment, the relevant components of the laser and the geometric dimensions of each part are as follows:

[0074] (1) The total cavity length of both the first laser resonator and the second laser resonator is: 179 mm, and the beam sizes at various positions in the two resonators are as Figures 5 - 6 shown. Here, the beam size is the spot radius size of the laser at various positions in the resonator simulated by the ABCD matrix.

[0075] (2) Crystals: C1: 2×2×10 mm 3 , C2: 2×2×10 mm 3 , C4: 3×3×10 mm 3 , C3: 3×3×10 mm 3

[0076] (3) M1 is a plane mirror, M2 is a plane mirror, M3 is a plane mirror, M4 is a plano - concave mirror (concave surface curvature 50 mm), M5 is a plano - concave mirror (concave surface curvature 50 mm), M6 is a plane mirror. Among them, the lens M4 is made of a material with high ultraviolet transmittance, such as JGS1 quartz glass, CaF2, MgF2.

[0077] (4) C1 and C2 are respectively in close contact with M1 and M2. The distance between M1 - M3 is: 20 mm, the distance between M2 - M3 is: 20 mm, the distance between M3 - M4 is: 24 mm, the distance between M4 - M5 is: 90 mm, C4 is at the middle position between M4 - M5, the distance between M5 - M6 is: 45 mm, and C3 is in close contact with M6.

[0078] (5) In the 526 - nm laser resonator formed by M1 - M4 - M5 - M6, the waist radius at the C1 crystal is 58 μm, the waist radius at the O2 crystal is 57 μm, and the waist radius at the O1 crystal is 51 μm. In the 725 - nm laser resonator formed by M1 - M3 - M4 - M5 - M6, the waist radius at the C2 crystal is 69 μm, the waist radius at the O2 crystal is 67 μm, and the waist radius at the O1 crystal is 59 μm.

[0079] Example 2: The difference between this example and Example 1 is that the first birefringent filter BRF1 and the second birefringent filter BRF2 are removed, and the remaining components and parameters are exactly the same. Due to the absence of the frequency selection effect of the birefringent filter, Pr 3+ : The SRA crystal will emit the wavelength corresponding to the fluorescence peak. C1 emits a laser with a wavelength of 525 nm, C2 emits a laser with a wavelength of 725 nm, and finally the laser wavelength emitted from M4 is 192.7 nm.

[0080] Example 3: Compared with Example 2, in this example, the first laser crystal and the second laser crystal are replaced from Pr 3+ :SRA to Pr 3+ :YLF, and the remaining optical components and parameters are exactly the same. The center wavelength of the 3 P1→ 3 H5 radiative transition is at 522 nm, 3 P0→ 3 The center wavelength of the F4 radiative transition is at 720 nm. After two intracavity frequency conversions, the laser wavelength emitted from M4 is 191.5 nm.

[0081] Example 4: Compared with Example 2, in this example, the first laser crystal and the second laser crystal are replaced from Pr 3+ :SRA to Pr 3+ :LMA (Pr 3+ :LaMgAl 11 [[ID=I28]]O 19 ), and the remaining optical components and parameters are exactly the same. The center wavelength of the 3 P1→ 3 H5 radiative transition is at 530 nm, 3 P0→ 3 The center wavelength of the F4 radiative transition is at 728 nm. After two intracavity frequency conversions, the laser wavelength emitted from M4 is 194.3 nm.

[0082] In this specification, each example is described in a progressive manner. The key point of each example is to illustrate the differences from other examples. For the same and similar parts among the examples, reference can be made to each other. For the device disclosed in the examples, since it corresponds to the method disclosed in the examples, the description is relatively simple, and reference can be made to the description in the method part for relevant parts.

[0083] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A all-solid-state continuous-wave vacuum ultraviolet laser using a double-resonant cavity, characterized in that, Comprising: A first pump source LD1, a first mirror M1, a first laser crystal C1, a second pump source LD2, a second mirror M2, a second laser crystal C2, a third mirror M3, a fourth mirror M4, a fifth mirror M5, a sixth mirror M6, a first nonlinear optical crystal O1, and a second nonlinear optical crystal O2; Wherein, the first mirror M1, the first laser crystal C1, the fourth mirror M4, the fifth mirror M5, and the sixth mirror M6 form a first laser resonator; The second mirror M2, the second laser crystal C2, the third mirror M3, the fourth mirror M4, the fifth mirror M5, and the sixth mirror M6 form a second laser resonator; The first nonlinear optical crystal O1 is disposed between the fifth mirror M5 and the sixth mirror M6, doubling the 526 nm laser generated by the first laser resonator into a second harmonic laser of 263 nm; The second nonlinear optical crystal O2 is disposed between the fourth mirror M4 and the fifth mirror M5, sum-frequency mixing the 725 nm fundamental frequency laser generated by the second laser resonator and the 263 nm second harmonic laser generated by the first nonlinear optical crystal O1 to generate a vacuum ultraviolet laser of 193 nm ± 2 nm, and outputting same through the fourth mirror M4.

2. The all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity according to claim 1, characterized in that, A first birefringent filter BRF1 is inserted into the optical cavity formed by the first mirror M1 and the third mirror M3; a second birefringent filter BRF2 is inserted into the optical cavity formed by the second mirror M2 and the third mirror M3.

3. The all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity according to claim 2, characterized in that, The materials of the first birefringent filter BRF1 and the second birefringent filter BRF2 are both quartz, with a thickness of 0.5 mm, and the optical axis C is parallel to the surface; The first birefringent filter BRF1 is inserted into the optical cavity formed by the first mirror M1 and the third mirror M3 at a Brewster angle of 57.28°, adjusting the angle A between the incident plane and the principal plane to 38.1°, and controlling the laser wavelength at 526 nm; The second birefringent filter BRF2 is inserted into the optical cavity formed by the second mirror M2 and the third mirror M3 at a Brewster angle of 57.15°, adjusting the angle α between the incident plane and the principal plane to 38.8°, and controlling the laser wavelength at 725 nm.

4. The all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity according to claim 1, characterized in that, The first laser crystal C1 and the second laser crystal C2 are both Pr 3+ :SRA, Pr 3+ :YLF or Pr 3+ :LMA; wherein, both light-passing end faces of the first laser crystal C1 are coated with an antireflection film of 526 nm; both light-passing end faces of the second laser crystal C2 are coated with an antireflection film of 725 nm.

5. The all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity according to claim 1, characterized in that, The first nonlinear optical crystal O1 is a second harmonic crystal for 526 nm laser, using a β-BBO crystal, a KDP crystal, or an ADP crystal, and its two light-passing end faces are coated with antireflection films of 725 nm, 526 nm, and 263 nm.

6. The all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity according to claim 1, characterized in that, The second nonlinear optical crystal O2 is a sum-frequency crystal for 725 nm laser and 263 nm laser, using a β-BBO crystal or a KBBF crystal, and its two light-passing end faces are coated with antireflection films of 725 nm, 526 nm, 263 nm, and 193 nm.

7. The all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity according to claim 1, wherein, Both the first pump source LD1 and the second pump source LD2 are laser diodes with spatial output or fiber-coupled output, and the laser wavelength they emit is 445 nm.

8. The all-solid-state continuous-wave vacuum ultraviolet laser using a double-resonator according to claim 1, characterized in that, The first endoscope M1 is a plane mirror coated with a dielectric film that has an anti-reflection coating for 445 nm and a high reflection coating for 526 nm, and is arranged close to the first pump source LD1; the second endoscope M2 is a plane mirror coated with a dielectric film that has a high transmission coating for 445 nm and a high reflection coating for 725 nm, and is arranged close to the second pump source LD2; The first laser crystal C1 is located between the first endoscope M1 and the second endoscope M2, and is arranged close to the first endoscope M1; the second laser crystal C2 is located between the second endoscope M2 and the third endoscope M3, and is arranged close to the second endoscope M2.

9. The all-solid-state continuous-wave vacuum ultraviolet laser using a double-resonant cavity according to claim 1, characterized in that, The third endoscope M3 is arranged between the first endoscope M1 and the fourth endoscope M4, and is placed at an angle of 45 degrees relative to the optical path M1M4; The third endoscope M3 is a plane mirror coated with a dielectric film that has a high transmission coating for 526 nm and a high reflection coating for 725 nm, and is used to separate the first laser resonator and the second laser resonator.

10. The all-solid-state continuous-wave vacuum ultraviolet laser using a double resonant cavity according to claim 1, characterized in that, The fourth endoscope M4 is a plano-concave mirror, serving as a common reflection mirror for the first laser resonator and the second laser resonator, and as an output mirror for 193 nm laser; on the side of the fourth endoscope M4 close to the resonator, it is coated with a dielectric film that has a high transmission coating for 193 nm, a high reflection coating for 526 nm, and a high reflection coating for 725 nm, and on the side far from the resonator, it is coated with a high transmission dielectric film for 193 nm; The fifth endoscope M5 is a plano-concave mirror, serving as a common reflection mirror for the first laser resonator and the second laser resonator; on the side of the fifth endoscope M5 close to the resonator, it is coated with a dielectric film that has a high reflection coating for 263 nm, a high reflection coating for 526 nm, and a high reflection coating for 725 nm; The sixth endoscope M6 is a plane mirror, serving as a common reflection mirror for the first laser resonator and the second laser resonator; on the side of the sixth endoscope M6 close to the resonator, it is coated with a dielectric film that has a high reflection coating for 263 nm, a high reflection coating for 526 nm, a high transmission coating for 600 - 650 nm, and a high reflection coating for 725 nm; The first nonlinear optical crystal O1 is arranged close to the sixth endoscope M6; the second nonlinear optical frequency crystal O2 is arranged at the waist of the optical cavity formed by the fourth endoscope M4 and the fifth endoscope M5.

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