All-solid-state continuous wave vacuum ultraviolet laser adopting double resonant cavities

Abstract

The invention relates to the technical field of lasers, in particular to an all-solid-state continuous wave vacuum ultraviolet laser adopting double resonant cavities, which is characterized in that 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; 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 a second laser resonant cavity; the first nonlinear optical crystal O1 is arranged between the fifth cavity mirror M5 and the sixth cavity mirror M6, and is used for performing frequency doubling on the 526-nm laser generated by the first resonant cavity into 263-nm frequency-doubled laser; the second nonlinear optical crystal O2 is arranged between the fourth cavity mirror M4 and the fifth cavity mirror M5, frequency sum is carried out on 725nm fundamental frequency laser generated by the second resonant cavity and 263nm frequency doubling laser generated by the first nonlinear optical crystal O1, and 193nm vacuum ultraviolet laser is generated and output through the fourth cavity mirror M4. The internal structure is simple, and the frequency conversion frequency is low.

Description

Technical Field

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

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

[0003] Currently, ArF excimer gas lasers are the only type of laser light source that can directly generate laser output at a vacuum ultraviolet wavelength of 193nm. They usually use a combination of rare gases and reactive gases under high pressure conditions to generate ultraviolet lasers. They have a large output power and occupy a large market share of lithography light sources. However, the working medium of ArF excimer lasers contains fluorine gas, which is toxic and corrosive, and there is a risk of endangering personal safety and environmental pollution. In addition, gas lasers have limited pulse repetition frequency (usually <10kHz), high peak power, poor beam quality, and poor coherence, which limits their application in detection.

[0004] Compared with gas lasers, solid 193nm laser sources have the advantages of high repetition frequency, good beam quality, good coherence, small size, and adjustable pulse width. 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 meet the needs of applications such as fiber grating writing, angle-resolved photoelectron spectroscopy experiments, semiconductor chip defect detection, and ArF excimer gas laser seed injection.

[0005] For solid-state 193nm laser light sources, the selection of the fundamental frequency light source and the choice of the nonlinear optical frequency conversion path are crucial, which directly determines the efficiency and complexity of the entire laser system. Current solid-state 193nm lasers generally use near-infrared lasers as the fundamental frequency light source, and then obtain 193nm laser output through more than 3 intracavity or extracavity frequency conversions. For example, the paper "Advanced Photonics Nexus, 3, 026012, 2024" first obtains 258nm lasers through two frequency doublings of a 1030nm light source, and then achieves 193nm output through two sum-frequency additions with a 1553nm light source, which has undergone a total of 4 frequency conversions. In the paper "Optics Letters, 40, 5590-5593, 2015", a 275.5nm laser is first obtained through two frequency doublings of a 1102nm light source, and then a 234.1nm laser is obtained through sum-frequency additions with a 1560nm light source, and finally a 193.4nm output is achieved through sum-frequency additions with a 1110nm light source, which has also undergone 4 frequency conversions. Three fundamental frequency light sources (1102nm, 1560nm, 1110nm) were used. In the patent document CN118610880 A, the 773.6nm laser of alexandrite crystal was used as the fundamental frequency light source, and the nonlinear crystal was used for frequency doubling, tripling, and quadrupling to achieve the target wavelength 193.4nm output. In summary, the existing solid-state 193nm laser technology uses three or more nonlinear optical frequency conversions, which have the disadvantages of complex generation process, severe energy attenuation, low conversion efficiency, high production cost, and poor reliability.

[0006] Therefore, how to provide a 193nm ultraviolet laser with a simple structure and a small number of frequency conversion times has become a technical problem that technical personnel in this field need to solve urgently. Summary of the invention

[0007] In view of this, the present invention provides an all-solid-state continuous-wave vacuum ultraviolet laser using a dual-resonance cavity, which has a simple internal structure and requires fewer frequency conversions.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A full 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 constitute a first laser resonant cavity;

[0011] 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 constitute a second laser resonant cavity;

[0012] The first nonlinear optical crystal O1 is disposed between the fifth cavity mirror M5 and the sixth cavity mirror M6, and frequency-doubles the 526nm laser generated by the first resonant cavity into a 263nm frequency-doubled laser;

[0013] The second nonlinear optical crystal O2 is arranged between the fourth cavity mirror M4 and the fifth cavity mirror M5, and performs frequency summing of the 725nm fundamental frequency laser generated by the second resonant cavity and the 263nm frequency-doubled laser generated by the first nonlinear optical crystal O1 to generate 193nm±2nm vacuum ultraviolet laser, which is output through the fourth cavity mirror M4.

[0014] Furthermore, a first birefringence filter BRF1 (Birefringence Filter) is inserted into the optical cavity formed by the first cavity mirror M1 and the third cavity mirror M3; a second birefringence filter BRF2 is inserted into the optical cavity formed by the second cavity mirror M2 and the third cavity mirror 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 cavity mirror M1 and the third cavity mirror M3 at a Brewster angle of 57.28°, and the angle A between the incident surface and the main plane is adjusted to 38.1°, and the laser wavelength is controlled at 526nm;

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

[0018] Furthermore, the first laser crystal C1 and the second laser crystal C2 are both Pr 3+ :SRA、Pr 3+ :YLF or Pr 3+ :LMA; wherein the two light-passing end faces of the first laser crystal C1 are coated with a 526nm anti-reflection film; the two light-passing end faces of the second laser crystal C2 are coated with a 725nm anti-reflection film.

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

[0020] Furthermore, the second nonlinear optical crystal O2 is a sum frequency crystal of 725nm laser and 263nm laser, using β-BBO crystal or KBBF crystal, and its two light-transmitting end faces are plated with 725nm, 526nm, 263nm and 193nm anti-reflection films.

[0021] Furthermore, both the first pump source LD1 and the second pump source LD2 are laser diodes with spatial output or fiber-coupled output, and the wavelength of the lasers emitted by them is 445 nm.

[0022] Further, the first cavity mirror M1 is a plane mirror, coated with a dielectric film with 445nm anti-reflection and 526nm 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 445nm high transmission and 725nm 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 disposed 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 disposed close to the second cavity mirror M2.

[0024] Further, the third cavity mirror M3 is disposed 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 high transmittance at 526nm and high reflectivity at 725nm, and is used to separate the first laser resonant cavity and the second laser resonant cavity.

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

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

[0028] The sixth cavity mirror M6 is a plane mirror, serving as a common reflection cavity mirror of the first laser resonant cavity and the second laser resonant cavity; the side of the sixth cavity mirror M6 close to the resonant cavity is coated with a dielectric film with 263nm high reflection, 526nm high reflection, 600-650nm high transmittance and 725nm high reflection;

[0029] The first nonlinear optical crystal O1 is arranged close to the sixth cavity mirror M6; the second nonlinear optical crystal O2 is arranged at the beam waist of the optical cavity formed by the fourth cavity mirror M4 and the fifth cavity 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 frequency light wavelengths used in the present invention are 526nm and 725nm, and only two frequency conversions are required to obtain 193nm laser output. Compared with the previous 3 to 5 frequency conversions, the nonlinear optical conversion process is less and the overall conversion efficiency is higher.

[0032] 2. The first laser resonant cavity and the second laser resonant cavity of the present invention share the cavity mirrors M3, M4 and M5, and the two resonant cavities are separated by the cavity mirror M3. The two resonant cavities constitute a multi-mirror folded cavity. A total of 4 beam waist positions are designed in the two resonant cavities, and laser crystals C1, C2 and 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 resonant cavities respectively, and accurately controls the oscillating laser wavelengths at 526nm and 725nm, with narrow spectrum lines and stable output. At the same time, BRF also makes the output wavelength of the laser have a certain degree of tunability around 193nm, which can meet various special needs, such as precise alignment with the wavelength of ArF excimer gas laser when used as a seed source.

[0034] 4. The present invention carefully screens rare earth ions and matrix crystals to determine the 3+ :SRA crystal is used as the working medium to generate 193nm solid laser. 3 P1→ 3 The central wavelength of H5 radiation transition is 525nm, and the radiation bandwidth is 9.8nm. Through the frequency selection of BRF, 526nm laser can be easily obtained. 3 P0→ 3 The central wavelength of F4 radiation transition is 725nm, and the radiation bandwidth is 4.35nm. By using BRF, it is easy to lock the output laser at 725nm. 3+The high-efficiency emission of the SRA crystal at 526nm and 725nm ensures that the vacuum ultraviolet laser output with a precise wavelength of 193nm can be achieved through further intracavity frequency conversion. In addition, the large bandwidth of its fluorescence emission also enables the laser to have a certain wavelength tuning capability near 193nm, which can be adjusted according to actual needs, only by fine-tuning the BRF and nonlinear optical crystal.

[0035] In summary, the present invention reduces the frequency conversion steps for generating 193nm solid-state laser, improves conversion efficiency, reduces the size of the device, simplifies the internal structure, and has tunable wavelength, good reliability, easy maintenance and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0037] Figure 1 This is a schematic structural diagram of an all-solid-state continuous-wave vacuum ultraviolet laser using a dual-resonance cavity provided in Example 1 of the present invention.

[0038] Figure 2 Schematic diagram of the optical path of the fundamental frequency laser through the birefringent filter in Example 1 of the present invention.

[0039] Figure 3 Schematic diagram of the transmission characteristics (α=38.1°, d=0.5 mm) of the first birefringent filter BRF1 in Example 1 of the present invention.

[0040] Figure 4 Schematic diagram of the transmission characteristics (α=38.8°, d=0.5 mm) of the second birefringent filter BRF2 in Example 1 of the present invention.

[0041] Figure 5 This is a schematic diagram of the beam sizes at various positions in the first laser resonant cavity surrounded by M1-M4-M5-M6 in Example 1 of the present invention.

[0042] Figure 6 This is a schematic diagram of the beam sizes at various positions in the second laser resonant cavity surrounded by M2-M3-M4-M5-M6 in Example 1 of the present invention. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Embodiment 1: The output wavelength of the vacuum ultraviolet laser in this embodiment is 193nm, and the specific structure is as follows Figure 1 As shown, it includes: 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;

[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 constitute a first laser resonant cavity;

[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 constitute a second laser resonant cavity;

[0047] A first birefringent filter BRF1 is inserted into the M1M3 optical cavity formed by the first cavity mirror M1 and the third cavity mirror M3; a second birefringent filter BRF2 is inserted into the M2M3 optical cavity 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 526nm and 725nm.

[0048] The first nonlinear optical crystal O1 is disposed between the fifth cavity mirror M5 and the sixth cavity mirror M6 to frequency-double the 526nm laser generated by the first resonant cavity into a 263nm frequency-doubled laser.

[0049] The second nonlinear optical crystal O2 is arranged between the fourth cavity mirror M4 and the fifth cavity mirror M5, and performs frequency summation of the 725nm fundamental frequency laser generated by the second resonant cavity and the 263nm doubled frequency laser generated by the first nonlinear optical crystal O1 to generate a 193nm vacuum ultraviolet laser, which is output through the fourth cavity mirror M4.

[0050] In order to ensure the effective convergence of the pump light, a focusing lens F1 is set between the first pump source LD1 and the first mirror cavity M1, and a focusing lens F2 is set between the second pump source LD2 and the second mirror cavity M2. The focal lengths of F1 and F2 are both 100 mm. 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 the optical axis C is parallel to the surface. The first birefringent filter BRF1 is inserted into the M1M3 optical cavity composed of the first cavity mirror M1 and the third cavity mirror M3 at a 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 line of the birefringent filter plane) and the main plane (the plane formed by the normal line 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] The first birefringent filter BRF1 is set at Brewster's angle θ b Insert into the laser resonant cavity, the propagation optical path of the fundamental frequency laser is as follows Figure 2 As shown. Due to the birefringence effect, the incident o-light and e-light will have a certain phase difference after passing through the BRF:

[0053]

[0054] Where λ is the incident wavelength, n o and n e are the refractive indices of ordinary light and extraordinary light, d is the thickness of BRF, and β is the angle between the optical axis and the ordinary light wave vector. The angle between the incident plane (the plane formed by the incident light and the normal line of the birefringent filter plane) and the principal plane (the plane formed by the normal line 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-light and e-light passing through the first birefringent filter BRF1 will interfere when emitted from the back surface, and the single-pass transmittance of BRF1 can be calculated from the interference light intensity. When polarized light is incident at the Brewster angle, the transmittance can be expressed as:

[0057]

[0058] Among them, φ represents the angle between the electric displacement vector of the o-light and the incident light, and:

[0059] sinφ=cotβ·tnaθ b (4)

[0060] According to the above formula, the tuning effect of BRF1 on the laser wavelength after it is inserted into the resonant cavity can be theoretically simulated. Taking the Brewster angle as 57.28° and the birefringence Δn=n e -n oIt is about 0.009. Taking different thicknesses d and tuning angles α, the following conclusions can be drawn from the calculation results of formula (3): At the same tuning angle α, the greater the thickness of the BRF, the narrower its main transmittance peak will be compressed. As the thickness of BRF1 increases, the interval between the transmittance peaks becomes smaller and smaller. At this time, multi-wavelength output may appear within the gain range of the laser crystal. In order to minimize the insertion loss of BRF1 while taking into account its mechanical strength, the thickness d of BRF1 is optimized to 0.5mm. 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, it is obtained that when the transmittance of 526nm is 1 under the condition of d=0.5mm, the corresponding α=38.1° is obtained. Its transmittance curve is as follows 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 M2M3 optical cavity composed of the second cavity mirror M2 and the third cavity mirror M3 at a Brewster angle of 57.15°, and the angle α between the incident plane (the plane formed by the incident light and the normal line of the birefringent filter plane) and the main plane (the plane formed by the normal line of the birefringent filter plane and the optical axis) is adjusted to 38.8°, and the oscillation laser wavelength is precisely controlled at 725nm. Its transmittance curve is shown in the attached figure. 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 0.5at.%; wherein, the two light-passing end faces of the first laser crystal C1 are coated with a 526nm anti-reflection film, and emit 526nm laser under the feedback of the 526nm laser resonant cavity. The two light-passing end faces of the second laser crystal C2 are coated with a 725nm anti-reflection film, and emit 725nm laser under the feedback of the 725nm laser resonant cavity.

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

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

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

[0066] The first cavity mirror M1 is a plane mirror, coated with a dielectric film with 445nm anti-reflection and 526nm 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 445nm high transmittance and 725nm 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 disposed 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 high transmittance at 526nm and high reflectivity at 725nm, and is used to separate the first laser resonant cavity from the second laser resonant cavity.

[0069] The fourth cavity mirror M4 is a plano-concave mirror, serving as a common reflection cavity mirror for the first laser resonant cavity and the second laser resonant cavity, as well as an output mirror for the 193nm laser. The fourth cavity mirror M4 is coated with a dielectric film with 193nm high transmittance, 526nm high reflection and 725nm high reflection on the side close to the resonant cavity, and is coated with a 193nm high transmittance dielectric film on the side away from the resonant cavity.

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

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

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

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

[0074] (1) The total cavity length of the first laser resonant cavity and the second laser resonant cavity is 179 mm. The beam size at each position of the two resonant cavities is as follows: Figure 5-Figure 6 As shown, the beam size here is the spot radius size of the laser at each position in the resonant cavity simulated by the ABCD matrix.

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

[0076] (3) M1 flat mirror, M2 flat mirror, M3 flat mirror, M4 flat concave mirror (concave curvature 50 mm), M5 flat concave mirror (concave curvature 50 mm), M6 flat mirror, where the lens M4 is made of a material with high UV transmittance, such as JGS1 quartz glass, CaF2, and MgF2.

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

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

[0079] Embodiment 2: The difference between this embodiment and embodiment 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. Since there is no frequency selection effect of the birefringent filter, Pr 3+ : The SRA crystal will emit the wavelength corresponding to the fluorescence peak, C1 will emit 525nm laser, C2 will emit 725nm laser, and finally the laser wavelength emitted by M4 is 192.7nm.

[0080] Embodiment 3: Compared with Embodiment 2, in this embodiment, the first laser crystal and the second laser crystal are made of Pr 3+ :SRA replaced by Pr 3+ :YLF, the rest of the optical components and parameters are exactly the same. 3 P1→ 3 The central wavelength of the H5 radiation transition is 522nm. 3 P0→ 3 The central wavelength of F4 radiation transition is 720nm, and the wavelength of the laser emitted by M4 after two intracavity frequency conversions is 191.5nm.

[0081] Embodiment 4: Compared with Embodiment 2, in this embodiment, the first laser crystal and the second laser crystal are made of Pr 3+ :SRA replaced by Pr 3+ :LMA(Pr 3+ :LaMgAl 11 O 19 ), the rest of the optical components and parameters are exactly the same. 3 P1→ 3 The central wavelength of H5 radiation transition is 530nm. 3 P0→ 3 The central wavelength of F4 radiation transition is 728nm, and the wavelength of the laser emitted by M4 after two intracavity frequency conversions is 194.3nm.

[0082] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0083] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An all-solid-state continuous-wave vacuum ultraviolet laser using a dual-resonance cavity, characterized in that: include: 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; 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 constitute a first laser resonant cavity; 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 constitute a second laser resonant cavity; The first nonlinear optical crystal O1 is disposed between the fifth cavity mirror M5 and the sixth cavity mirror M6, and frequency-doubles the 526nm laser generated by the first resonant cavity into a 263nm frequency-doubled laser; The second nonlinear optical crystal O2 is arranged between the fourth cavity mirror M4 and the fifth cavity mirror M5, and performs frequency summing of the 725nm fundamental frequency laser generated by the second resonant cavity and the 263nm frequency-doubled laser generated by the first nonlinear optical crystal O1 to generate 193nm±2nm vacuum ultraviolet laser, which is output through the fourth cavity mirror M4.

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

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

4. The all-solid-state continuous-wave vacuum ultraviolet laser using a dual-resonance 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 the two light-passing end faces of the first laser crystal C1 are coated with a 526nm anti-reflection film; the two light-passing end faces of the second laser crystal C2 are coated with a 725nm anti-reflection film.

5. The all-solid-state continuous-wave vacuum ultraviolet laser using a dual-resonance cavity according to claim 1, characterized in that: The first nonlinear optical crystal O1 is a frequency doubling crystal for 526nm laser, and is made of β-BBO crystal, KDP crystal or ADP crystal, and its two light-transmitting end faces are plated with 725nm, 526nm and 263nm anti-reflection films.

6. The all-solid-state continuous-wave vacuum ultraviolet laser using a dual-resonance cavity according to claim 1, characterized in that: The second nonlinear optical crystal O2 is a sum frequency crystal of 725nm laser and 263nm laser, adopts β-BBO crystal or KBBF crystal, and its two light-transmitting end faces are plated with 725nm, 526nm, 263nm and 193nm anti-reflection films.

7. The all-solid-state continuous-wave vacuum ultraviolet laser using a dual-resonance cavity according to claim 1, characterized in that: The first pump source LD1 and the second pump source LD2 are both laser diodes with spatial output or fiber-coupled output, and the wavelength of the lasers emitted by them is 445 nm.

8. The all-solid-state continuous-wave vacuum ultraviolet laser using a dual-resonance cavity according to claim 1, characterized in that: The first cavity mirror M1 is a plane mirror, coated with a dielectric film with 445nm anti-reflection and 526nm 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 445nm high transmittance and 725nm 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 disposed 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 disposed close to the second cavity mirror M2.

9. The all-solid-state continuous-wave vacuum ultraviolet laser using a dual-resonance cavity according to claim 1, characterized in that: The third cavity mirror M3 is disposed 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; The third cavity mirror M3 is a plane mirror coated with a dielectric film with high transmittance at 526nm and high reflectivity at 725nm, and is used to separate the first laser resonant cavity and the second laser resonant cavity.

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

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