A high-efficiency stable all-solid-state ultraviolet laser

Abstract

The application discloses a kind of high-efficiency stable all-solid-state ultraviolet laser, comprising: pump source, focusing system, resonator input mirror, laser crystal, frequency doubling crystal, frequency doubling output mirror and frequency doubling full mirror;Pump light emitted by pump source successively passes through focusing system, resonator input mirror, is irradiated on laser crystal, again by frequency doubling output mirror reflection focusing, passes through frequency doubling crystal frequency doubling incidence to frequency doubling full mirror, is reflected by frequency doubling full mirror again and passes through frequency doubling crystal, finally is output by laser output mirror;Resonator input mirror, frequency doubling output mirror and frequency doubling full mirror form three-mirror resonator;Laser crystal and frequency doubling crystal are all long crystal, and are respectively placed at the waist of two arms of three-mirror resonator.This application calculates the waist area size in resonator based on ABCD matrix, can improve resonator fundamental frequency light power density, and simultaneously, in combination with the applicable selection of different length crystal, the efficient and stable work of laser can be realized.

Description

Technical Field

[0001] This invention relates to the field of laser and nonlinear optics technology, and more specifically to a highly efficient and stable all-solid-state ultraviolet laser. Background Technology

[0002] Currently, diode-pumped solid-state lasers (DPSSLs) possess numerous advantages such as small size, high efficiency, simple structure, and long lifespan, making them a research hotspot in recent years and finding wide applications in scientific research, medicine, and military fields. Among the many research areas of DPSSLs, ultraviolet frequency doubling output is an important direction.

[0003] In frequency-converting lasers based on DPSSL technology, the frequency doubling and sum-frequency effects of nonlinear optical crystals can be utilized to convert the fundamental frequency light in the near-infrared band to the visible, ultraviolet, and even deep ultraviolet bands, meeting a wider range of needs in various fields, such as precision micromachining, gene sequencing, optical data storage, atmospheric detection, emission spectroscopy, Raman spectroscopy, ultra-high energy resolution photoelectron spectroscopy, and photoelectron emission microscopy. The frequency doubling efficiency of the nonlinear crystal is related to the fundamental frequency power density; the higher the fundamental frequency power density, the higher the frequency doubling efficiency and the higher the output frequency-doubled light power. By using a tri-concave resonant cavity mirror, the resonant cavity mode beam waist is reduced, increasing the fundamental frequency power density. However, an extremely small cavity mode beam waist can cause end-face damage to both the laser crystal and the frequency-doubling crystal. Therefore, it is necessary to increase the crystal length to increase the crystal end-face spot area, mitigate crystal end-face damage, and improve the stability of the laser. Therefore, for all-solid-state frequency-doubled lasers pumped by laser diodes, the energy conversion process includes pump light to fundamental light and fundamental light to frequency-doubled light. When the resonant cavity mode beam waist is too large, it will lead to a decrease in frequency doubling efficiency. A very small cavity mode beam waist will damage the crystal end face. These factors accumulate together and cause a more significant change in the final output, making it more difficult to operate efficiently and stably.

[0004] Therefore, how to improve the fundamental frequency optical power density of the resonant cavity and reduce optical damage to the crystal end face so that the laser can work efficiently and stably in the ultraviolet band is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a highly efficient and stable all-solid-state ultraviolet laser and a frequency-doubled laser. Based on the ABCD matrix, the beam waist area inside the resonant cavity is calculated to improve the fundamental frequency optical power density of the resonant cavity. Combined with the change of crystal length, the laser can operate efficiently and stably.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A high-efficiency and stable all-solid-state ultraviolet laser includes: a pump source, a focusing system, a resonant cavity input mirror, a laser crystal, a frequency-doubling crystal, a frequency-doubling output mirror, and a frequency-doubling total reflection mirror;

[0008] The pump light emitted by the pump source passes sequentially through the focusing system and the resonant cavity input mirror, and then irradiates the laser crystal to generate a fundamental frequency visible laser. The laser light is reflected and focused by the frequency doubling output mirror, and then incident on the frequency doubling crystal to double the wavelength of the fundamental frequency visible laser so that the wavelength of the doubled light is in the deep ultraviolet band. The laser light then passes through the frequency doubling total reflection mirror, is reflected by the frequency doubling total reflection mirror, passes through the frequency doubling crystal again, and is finally output through the laser output mirror.

[0009] The resonant cavity consists of an input mirror, a frequency-doubling output mirror, and a frequency-doubling total reflection mirror. Both the laser crystal and the frequency-doubling crystal are long crystals and are respectively placed at the waist of the two arms of the three-mirror resonant cavity.

[0010] Preferably, the Pr 3+ Fluoride-doped crystals include:

[0011] Praseodymium-doped lithium yttrium fluoride crystals Pr 3+ YLiF4, praseodymium-doped gadolinium fluoride lithium crystal Pr 3+ GdLiF4, or praseodymium-doped lutetium fluoride crystals Pr 3+ LuLiF4, or yttrium praseodymium aluminate crystals Pr 3+ :YAlO3.

[0012] Preferably, the Pr 3+ In fluoride-doped crystals, the energy level transitions involved are Pr 3+ Ionic 3 P1→ 3 H5 has an emission wavelength around 522nm; both light-transmitting end faces of the laser crystal are coated with an anti-reflection film of 400-800nm.

[0013] Preferably, the pump source is a distributed feedback LD with a center wavelength of 444nm.

[0014] Preferably, the focusing system includes a plurality of lenses for focusing the pump beam into the laser crystal;

[0015] The parameters of each lens are set based on the parameters of the three-mirror resonant cavity, so that the beam size of the pump light matches that of the fundamental frequency light.

[0016] Preferably, the resonant cavity input mirror is a plano-concave mirror. The planar surface of the resonant cavity input mirror near the pump source is coated with a dielectric film that enhances the transmittance of 444nm pump light, and the concave surface is coated with a dielectric film that enhances the transmittance of 444nm, enhances the transmittance of 600-800nm, and has high reflectivity of 522nm. The radius of curvature of the concave surface of the resonant cavity input mirror is 50mm.

[0017] The frequency doubling output mirror is a plano-concave mirror. The concave surface of the frequency doubling output mirror is coated with a dielectric film that enhances the reflection of 261nm, provides high reflectivity at 522nm, and enhances the reflection of 600-800nm. The planar surface is coated with an anti-reflection film of 200-800nm. The radius of curvature of the concave surface of the frequency doubling output mirror is 50mm.

[0018] The frequency-doubled total reflection mirror is a plano-concave mirror. The concave surface of the frequency-doubled total reflection mirror is coated with a dielectric film that provides high reflectivity for 261nm and 522nm and antireflection for 600-800nm, while the planar surface is coated with an antireflection film for 600-800nm. The radius of curvature of the concave surface of the frequency-doubled total reflection mirror is 50mm.

[0019] Preferably, the length of the laser crystal and the frequency doubling crystal is 10 mm.

[0020] Preferably, the frequency doubling crystal is a nonlinear optical crystal, and both light-transmitting end faces are coated with an anti-reflection film of 200-800nm.

[0021] Preferably, a pulse modulator is disposed in the three-mirror resonant cavity and is located in the optical path between the laser crystal and the frequency doubling output mirror;

[0022] The pulse modulator includes: an electro-optic Q-switching switch, an acousto-optic Q-switching switch, and a saturable absorber for passive Q-switching operation in the visible light band.

[0023] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a highly efficient and stable all-solid-state ultraviolet laser, comprising: a pump source, a focusing system, a resonant cavity input mirror, a laser crystal, a frequency doubling crystal, a frequency doubling output mirror, and a frequency doubling total reflection mirror; the resonant cavity input mirror, the frequency doubling output mirror, and the frequency doubling total reflection mirror form a three-mirror resonant cavity; both the laser crystal and the frequency doubling crystal are long crystals and are respectively placed at the beam waist of the two arms of the three-mirror resonant cavity; the present invention calculates the beam waist area in the resonant cavity based on the ABCD matrix, which can improve the fundamental frequency optical power density of the resonant cavity; at the same time, combined with the appropriate selection of crystals of different lengths, it can achieve efficient and stable operation of the laser. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 The attached image is Pr 3+ Schematic diagram of ion energy level structure;

[0026] Figure 2 The attached figure is a schematic diagram of the all-solid-state continuous wave 261nm laser structure of Embodiments 1 and 3 of the present invention;

[0027] Figure 3 The attached figure is a schematic diagram of the all-solid-state pulsed deep ultraviolet laser structure according to Embodiment 2 of the present invention;

[0028] Among them, 1 is the pump source, 2 is the focusing system, 3 is the resonant cavity input mirror, 4 is the laser crystal, 5 is the BBO frequency doubling crystal, 6 is the frequency doubling output mirror, 7 is the frequency doubling total reflection mirror, and 8 is the pulse modulator. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] like Figure 1 As shown, this embodiment of the invention discloses a high-efficiency and stable all-solid-state ultraviolet laser, including: a pump source 1, a focusing system 2, a resonant cavity input mirror 3, a laser crystal 4, a BBO frequency doubling crystal 5, a frequency doubling output mirror 6, and a frequency doubling total reflection mirror 7;

[0031] Pump light emitted from pump source 1 passes sequentially through focusing system 2 and resonant cavity input mirror 3, and then irradiates laser crystal 4 to generate fundamental frequency visible laser. It is reflected and focused by frequency doubling output mirror 6 and incident on frequency doubling crystal 5 to double the fundamental frequency visible laser so that the wavelength of the frequency-doubled light is in the deep ultraviolet band. After passing through frequency doubling total reflection mirror 7, it is reflected again by frequency doubling total reflection mirror 7 and then passes through the frequency doubling crystal 5, and finally output through laser output mirror 6.

[0032] The resonant cavity consists of a resonant input mirror 3, a frequency-doubling output mirror 6, and a frequency-doubling total reflection mirror 7, forming a three-mirror resonant cavity. The laser crystal 4 and the frequency-doubling crystal 5 are both long crystals and are placed at the waist of the two arms of the three-mirror resonant cavity, respectively.

[0033] To further optimize the above technical solution, the laser crystal 4 is Pr 3+ Fluoride-doped crystals include:

[0034] Praseodymium-doped lithium yttrium fluoride crystals Pr 3+ YLiF4, praseodymium-doped gadolinium fluoride lithium crystal Pr 3+ GdLiF4, or praseodymium-doped lutetium fluoride crystals Pr 3+ LuLiF4, or yttrium praseodymium aluminate crystals Pr 3+ :YAlO3.

[0035] The energy level transitions involved are Pr 3+ Ionic 3 P1→ 3 H5 emits light at a wavelength around 522nm; both light-transmitting end faces of laser crystal 4 are coated with an anti-reflection film of 400-800nm.

[0036] To further optimize the above technical solution, pump source 1 is a distributed feedback LD with a center wavelength of 444nm.

[0037] To further optimize the above technical solution, the focusing system 2 includes multiple lenses for focusing the pump beam into the laser crystal 4;

[0038] The parameters of each lens are set based on the parameters of the three-mirror resonant cavity, so that the beam size of the pump light matches that of the fundamental frequency light.

[0039] To further optimize the above technical solution, the resonant cavity input mirror 3 is a plano-concave mirror. The plane of the resonant cavity input mirror 3 near the pump source 1 is coated with a dielectric film that enhances the transmission of 444nm pump light, and the concave surface is coated with a dielectric film that enhances the transmission of 444nm, 600-800nm, and 522nm. The radius of curvature of the concave surface of the resonant cavity input mirror (3) is 50mm.

[0040] The frequency doubling output mirror 6 is a plano-concave mirror. The concave surface of the frequency doubling output mirror 6 is coated with a dielectric film that enhances the reflection of 261nm, provides high reflection of 522nm, and enhances the reflection of 600-800nm. The planar surface is coated with an anti-reflection film of 200-800nm. The radius of curvature of the concave surface of the frequency doubling output mirror 6 is 50mm.

[0041] The frequency-doubled total reflection mirror 7 is a plano-concave mirror. The concave surface of the frequency-doubled total reflection mirror 7 is coated with a dielectric film that provides high reflectivity for 261nm and 522nm and anti-reflection for 600-800nm, while the planar surface is coated with an anti-reflection film for 600-800nm. The radius of curvature of the concave surface of the frequency-doubled total reflection mirror 7 is 50mm.

[0042] To further optimize the above technical solution, the lengths of laser crystal 4 and frequency doubling crystal 5 are 10mm.

[0043] To further optimize the above technical solution, the frequency doubling crystal 5 is a nonlinear optical crystal, including LiB3O5 and CsLiB6O. 10 Specifically, the nonlinear optical crystal can be made of β-BaB2O4, processed along the 522nm class I frequency doubling direction, with a chamfer of θ = 49° and φ = 0°, and both light-transmitting end faces are coated with a 200-800nm ​​anti-reflection film.

[0044] To further optimize the above technical solution, a pulse modulator 8 is installed inside the three-mirror resonant cavity and is located in the optical path between the laser crystal 4 and the frequency doubling output mirror 6.

[0045] The pulse modulator 8 includes an electro-optic Q-switching switch, an acousto-optic Q-switching switch, and a saturable absorber for passive Q-switching operation in the visible light band to obtain visible fundamental frequency light in pulse form.

[0046] Calculation of the beam waist area within the resonant cavity

[0047] The ABCD matrix, also known as the ray transfer matrix, essentially transforms the alternating operations of paraxial ray tracing formulas across different refractive surfaces into matrix operations using linear algebra. The ABCD matrix, or ray transfer matrix, is a 2x2 matrix describing the effect of an optical element within a laser beam. It can be used in ray optics where light travels geometrically as rays, or in the transmission of Gaussian beams.

[0048] When the angle is very small (paraxial approximation), there is a linear relationship between coordinates r and θ before and after passing the optical element. The following matrix equation can be used to calculate the changes in parameters of the optical element:

[0049]

[0050] Where r is the lateral offset, θ is the offset angle, and the spherical mirror reflection matrix is... Where R represents the radius of curvature of the spherical mirror, with positive values ​​for convex mirrors and negative values ​​for concave mirrors. From formula (1), we can calculate the ray matrix for one round trip in the cavity of the spherical mirror:

[0051]

[0052] in:

[0053]

[0054] Where R1 and R2 are the radii of curvature of the two mirrors in the resonant cavity, and L is the length of the resonant cavity.

[0055] The ray matrix after n round trips is further calculated using formula (2), and finally obtained as follows:

[0056]

[0057] in:

[0058]

[0059] This indicates the angle between the laser beams propagating paraxially within the cavity.

[0060] As light continuously reflects back and forth between the two mirrors, it is essential to ensure that the light never leaves the resonant cavity during its back-and-forth reflections, i.e., to maintain a stable cavity. The stability condition is as follows:

[0061]

[0062] As can be seen from the above formulas, it is essential to ensure that the resonant cavity is stable and to minimize the beam waist within the cavity to obtain a higher optical power density. Therefore, we selected three concave mirrors with a radius of curvature of 50mm as resonant cavity mirrors, employing a concentric critical cavity design. Two crystals were placed at the minimum beam waist points on the two arms of the resonant cavity to obtain a smaller light spot and improve the laser's optical conversion efficiency.

[0063] (2) High-efficiency and stable operation of frequency-doubled lasers

[0064] For frequency-doubled lasers, the frequency doubling conversion stage, i.e., the efficiency of the nonlinear optical crystal, needs to be considered. Currently, nonlinear optical crystals capable of frequency doubling to 522nm include β-BaB₂O₄ (β-BBO), LBO (LiB₃O₅), and CLBO (CsLiB₆O₄). 10Among these four crystals, β-BBO and LBO exhibit excellent overall performance, mature growth processes, and widespread market use. Of these four crystals, β-BBO has the largest nonlinear optical coefficient, the highest conversion efficiency, the smallest refractive index temperature coefficient, and the largest frequency doubling temperature bandwidth, thus best meeting the high efficiency and stability requirements of this invention. From a phase-matching perspective, the Type I frequency doubling phase-matching process involves two refractive indices (fundamental slow light, frequency doubling fast light), while the Type II frequency doubling phase-matching process involves three refractive indices (fundamental slow light, fundamental fast light, frequency doubling fast light). Temperature-induced refractive index changes have a greater impact on the latter; therefore, Type I frequency doubling phase matching has a larger temperature bandwidth than Type II frequency doubling phase matching, better meeting the stability requirements of this invention. Therefore, for the deep ultraviolet frequency doubling application of this invention, β-BBO is preferred as the frequency doubling crystal, processed along the Type I frequency doubling direction at 522nm, with a chamfer angle of (θ=49°, φ=0°). To improve the overall efficiency and stability of the laser, the mode beam waist within the resonant cavity should be minimized. Theoretically calculated, the beam waist size within the cavity is 102μm in diameter. Using a 5mm long BBO crystal, the spot diameter at the crystal end face is 104μm; using a 10mm long BBO crystal, the spot diameter at the crystal end face is 111μm. Therefore, this invention prefers a 10mm long BBO crystal as the frequency doubling crystal, which can effectively avoid end face damage. It is compatible with long Pr... 3+ Together with fluoride-doped crystals, this constitutes the preferred technical solution for the efficient and stable operation of the laser of the present invention.

[0065] Example 1: A fully solid-state continuous wave 261nm laser that can operate efficiently and stably.

[0066] like Figure 2 As shown, the device includes a pump source 1, a pump light focusing system 2, an input mirror 3, a laser crystal 4, a frequency doubling crystal 5, a frequency doubling output mirror 6, and a frequency doubling total reflection mirror 7. The pump source 1 is a DFB blue light LD with a center wavelength of 444nm and a maximum power of 3.5W; the focusing system 2 consists of multiple lenses, including concave-plano cylindrical lenses, convex-plano cylindrical lenses, and a biconvex circular lens with a focal length of 40mm; the resonant cavity input mirror 3 is a plano-concave mirror with a curvature of 50mm, its surface coated with an anti-reflection dielectric film for 417-446nm and a high-reflection dielectric film for 485-800nm; the laser crystal 4 is a Pr... 3+ LiYF4 crystal, Pr 3+The ion doping concentration is 0.5%, the length is 10mm, and the two light-transmitting end faces of the crystal are polished but not coated; the frequency doubling crystal 5 is a BBO crystal with a cutting angle of θ = 49° and φ = 0°, and both light-transmitting end faces of the nonlinear optical crystal are coated with a 200-800nm ​​anti-reflection dielectric film; the frequency doubling output mirror 6 is a plano-concave mirror with a curvature of 50mm, used to reflect 522nm laser light, and its concave surface is coated with a 522nm total reflection film (R = 99%) and a 261nm anti-reflection film (T). =95%), 600-800nm ​​anti-reflection dielectric film (used to suppress oscillation of 600-800nm ​​laser wavelength), and the plane is coated with 200-800nm ​​anti-reflection dielectric film; the frequency doubling total reflection mirror 7 is a plano-concave mirror with a curvature of 50mm, the concave surface is coated with 261nm, 522nm high reflectivity, 600-800nm ​​anti-reflection dielectric film (used to suppress oscillation of 600-800nm ​​laser wavelength), and the plane is coated with 600-800nm ​​anti-reflection dielectric film.

[0067] In this embodiment, the laser output also increases as the pump power increases. This test demonstrates that the present invention has the significant advantage of efficient and stable operation.

[0068] Example 2: A high-power all-solid-state pulsed deep ultraviolet laser that can operate efficiently and stably.

[0069] like Figure 3 As shown, the device includes a pump source 1, a pump light focusing system 2, a resonant cavity input mirror 3, a laser crystal 4, a frequency doubling crystal 5, a frequency doubling output mirror 6, a frequency doubling total reflection mirror 7, and a pulse modulator 8. Components 1-7 in this embodiment are the same as in embodiment 1, except that a pulse modulator 8 is added after the laser crystal 4. The pulse modulator 8 can be an electro-optic Q-switched switch, an acousto-optic Q-switched switch, or other saturable absorber capable of passive Q-switching in the visible light band. The DFB blue LD pump laser crystal 4 generates 522nm visible fundamental frequency light, which, after passing through the pulse modulator 8, forms pulsed fundamental frequency light within the resonant cavity formed by the input mirror 3, the frequency doubling output mirror 6, and the frequency doubling total reflection mirror 7. Frequency doubling occurs at the frequency doubling crystal 5, generating pulsed deep ultraviolet laser with a wavelength of 261nm, which is output from the frequency doubling output mirror 6.

[0070] Example 3: A solid-state continuous-wave deep ultraviolet laser that can operate efficiently and stably.

[0071] like Figure 1As shown, the device includes a pump source 1, a pump light focusing system 2, an input mirror 3, a laser crystal 4, a frequency doubling crystal 5, a frequency doubling output mirror 6, and a frequency doubling total reflection mirror 7. Components 1-7 in this embodiment are the same as in embodiment 1. The difference is that in this embodiment, the frequency doubling crystal 5 is a BBO crystal with a cutting angle of θ = 37.4° and φ = 0°. Both light-transmitting end faces of the nonlinear optical crystal are coated with a 200-800nm ​​anti-reflection dielectric film. The frequency doubling output mirror 6 is a plano-concave mirror with a curvature of 50mm, used to reflect 640nm laser light. Its concave surface is coated with a 640nm total reflection film (R = 99%), a 320nm anti-reflection film (T = 95%), and anti-reflection films for 500-630nm and 650-800nm. The dielectric film (used to suppress oscillations of 500-630nm and 650-800nm ​​laser wavelengths) is coated on the surface, and the plane is coated with a 200-800nm ​​anti-reflection dielectric film; the frequency-doubled total reflection mirror 13 is a plano-concave mirror with a curvature of 50mm, and the concave surface is coated with a 320nm and 640nm high-reflection dielectric film, and the 500-630nm and 650-800nm ​​anti-reflection dielectric film (used to suppress oscillations of 500-630nm and 650-800nm ​​laser wavelengths), and the plane is coated with a 500-630nm and 650-800nm ​​anti-reflection dielectric film. The DFB blue LD pump laser crystal 4 generates 640nm visible fundamental frequency light, which is first generated into 320nm deep ultraviolet laser after passing through the frequency-doubled crystal 5. After being reflected by the frequency-doubled total reflection mirror 7, the remaining fundamental frequency light passes through the frequency-doubled crystal 5 again and generates 320nm deep ultraviolet laser a second time. The deep ultraviolet lasers generated by the two processes are output from the frequency-doubled output mirror 6.

[0072] This invention employs a reduced resonant cavity mode waist and increased crystal length to improve frequency doubling conversion efficiency and mitigate crystal end-face damage. A three-concave resonant cavity is used to achieve an extremely small resonant cavity mode waist, increasing optical power density and improving frequency doubling conversion efficiency. The use of a long crystal increases the spot area at the crystal end face, reducing optical damage to the crystal end face. This allows for stable operation at high power levels for extended periods, extending the lifespan of the all-solid-state laser and expanding its application range. An 808nm Nd-doped laser is used for pumping. 3+ Traditional deep ultraviolet lasers use a laser crystal to generate a 1064nm fundamental frequency light, which is then passed through two frequency-doubling crystals to generate a 266nm fourth-harmonic laser. This type of structure requires two frequency doubling processes, resulting in low conversion efficiency. The laser of this invention undergoes only one frequency doubling, leading to significantly higher conversion efficiency. Therefore, compared to traditional solid-state laser technology, this invention offers significant advantages in terms of high efficiency and stable operation. Furthermore, this invention features a simple structure, small size, and light weight, which is beneficial for industrialization and mass production.

[0073] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0074] The above description of the disclosed embodiments enables those skilled in the art to make or use the 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 invention. Therefore, the invention is not 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 highly efficient and stable all-solid-state ultraviolet laser, characterized in that, include: Pump source (1), focusing system (2), resonant cavity input mirror (3), laser crystal (4), frequency doubling crystal (5), frequency doubling output mirror (6) and frequency doubling total reflection mirror (7); The pump light emitted by the pump source (1) passes sequentially through the focusing system (2) and the resonant cavity input mirror (3) and irradiates the laser crystal (4) to generate a fundamental frequency visible laser. It is reflected and focused by the frequency doubling output mirror (6) and incident on the frequency doubling crystal (5) to double the fundamental frequency visible laser so that the wavelength of the frequency doubling light is in the deep ultraviolet band. It then passes through the frequency doubling total reflection mirror (7), is reflected by the frequency doubling total reflection mirror (7) and passes through the frequency doubling crystal (5) again, and is finally output through the frequency doubling output mirror (6). The resonant cavity input mirror (3), frequency doubling output mirror (6) and frequency doubling total reflection mirror (7) form a three-mirror resonant cavity. The three-mirror resonant cavity is a concentric critical cavity, and the beam waist area in the resonant cavity is calculated based on the ABCD matrix. Both the laser crystal (4) and the frequency doubling crystal (5) are 10mm long crystals to reduce damage to the crystal end face, and are respectively placed at the minimum waist of the two arms of the three-mirror resonant cavity; the frequency doubling crystal (5) is β-BBO, processed along the 522nm type I frequency doubling direction, and the chamfer is set as follows: polar angle θ=49°, azimuth angle Φ=0°.

2. The high-efficiency and stable all-solid-state ultraviolet laser according to claim 1, characterized in that, The laser crystal is Pr 3+ Fluoride-doped crystals include: Praseodymium-doped lithium yttrium fluoride crystals Pr 3+ YLiF4, praseodymium-doped gadolinium fluoride lithium crystal Pr 3+ GdLiF4, or praseodymium-doped lutetium fluoride crystals Pr 3 + :LuLiF4.

3. The high-efficiency and stable all-solid-state ultraviolet laser according to claim 2, characterized in that, The Pr 3+ In fluoride-doped crystals, the energy level transitions involved are Pr 3+ Ionic 3 P1→ 3 H5, the emission wavelength is located near 522nm; both light-transmitting end faces of the laser crystal (4) are coated with a 400-800nm ​​anti-reflection film.

4. The high-efficiency and stable all-solid-state ultraviolet laser according to claim 1, characterized in that, The pump source (1) is a distributed feedback LD with a center wavelength of 444nm.

5. A high-efficiency and stable all-solid-state ultraviolet laser according to claim 1, characterized in that, The focusing system (2) includes multiple lenses for focusing the pump beam into the laser crystal (4); The parameters of each lens are set based on the parameters of the three-mirror resonant cavity, so that the beam size of the pump light matches that of the fundamental frequency light.

6. The high-efficiency and stable all-solid-state ultraviolet laser according to claim 1, characterized in that, The resonant cavity input mirror (3) is a plano-concave mirror. The plane of the resonant cavity input mirror (3) near the pump source (1) is coated with a dielectric film that enhances the transmission of 444nm pump light, and the concave surface is coated with a dielectric film that enhances the transmission of 444nm, 600-800nm, and 522nm. The radius of curvature of the concave surface of the resonant cavity input mirror (3) is 50mm. The frequency doubling output mirror (6) is a plano-concave mirror. The concave surface of the frequency doubling output mirror (6) is coated with a dielectric film that enhances the reflection of 261nm, provides high reflection of 522nm, and enhances the reflection of 600-800nm. The planar surface is coated with a 200-800nm ​​anti-reflection film. The radius of curvature of the concave surface of the frequency doubling output mirror (6) is 50mm. The frequency-doubled total reflection mirror (7) is a plano-concave mirror. The concave surface of the frequency-doubled total reflection mirror (7) is coated with a dielectric film that provides high reflectivity for 261nm and 522nm and antireflection for 600-800nm, while the planar surface is coated with an antireflection film for 600-800nm. The radius of curvature of the concave surface of the frequency-doubled total reflection mirror (7) is 50mm.

7. The high-efficiency and stable all-solid-state ultraviolet laser according to claim 1, characterized in that, The frequency doubling crystal (5) is a nonlinear optical crystal, and both light-transmitting end faces are coated with a 200-800nm ​​anti-reflection film.

8. A high-efficiency and stable all-solid-state ultraviolet laser according to claim 1, characterized in that, A pulse modulator (8) is provided in the three-mirror resonant cavity and is located in the optical path between the laser crystal (4) and the frequency doubling output mirror (6); The pulse modulator (8) includes: an electro-optic Q-switching switch, an acousto-optic Q-switching switch, and a saturable absorber for passive Q-switching operation in the visible light band.

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