Narrow-linewidth blue pulsed laser
By using a single-frequency pulsed laser module and an optical parametric oscillation module with a non-planar rotating ring cavity design, the problems of large linewidth, low energy, and poor beam quality of blue pulsed lasers have been solved, achieving high-energy, high-stability narrow-linewidth blue pulsed laser output, which is suitable for fields such as marine resource exploration and underwater laser communication.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI INST OF OPTICS & FINE MECHANICS CHINESE ACAD OF SCI
- Filing Date
- 2023-06-12
- Publication Date
- 2026-07-21
AI Technical Summary
Existing blue pulsed lasers suffer from problems such as large linewidth, low energy, poor beam quality, and poor stability, which limit their application in demanding fields.
An optical parametric oscillation module employing a single-frequency pulse laser module, a frequency doubling module, and a non-planar image rotating ring cavity design generates high-energy, high-beam-quality narrow-linewidth blue pulse lasers through multi-stage amplification and frequency conversion.
It achieves high-energy, high-beam-quality, and narrow-linewidth blue pulse laser output, improving system stability and making it suitable for fields such as marine resource exploration, underwater laser communication, and bioengineering.
Smart Images
Figure CN116914546B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of solid-state laser technology, and in particular to a narrow-linewidth blue pulse laser. Background Technology
[0002] Blue lasers possess characteristics such as short wavelength, low diffraction effect, and high energy, making them promising for applications in marine resource exploration, quantum communication, additive manufacturing, bioengineering, and spectral analysis. Since the blue light band falls within the ocean's transmission window, and the Fraunhofer dark line (486.1 nm) of the solar radiation spectrum also lies within this window, the development of high-energy, narrow-linewidth blue pulsed lasers offers advantages such as low absorption loss and high signal-to-noise ratio, significantly enhancing the performance of spaceborne and airborne marine radars and underwater laser communication systems.
[0003] Since no solid-state laser material has yet been discovered that can directly emit blue laser light, high-energy, narrow-linewidth blue lasers based on solid-state laser technology typically require multiple nonlinear frequency conversions, such as those based on Nd... 3+ The 1.06μm infrared laser from an ion laser is used to obtain 355nm ultraviolet laser by first frequency doubling and then summing the frequencies. Blue laser output is then obtained by using the 355nm ultraviolet laser to pump an optical parametric oscillator (OPO). However, this method involves ultraviolet lasers, which can cause damage to the optical thin film, limiting the efficiency, stability, and lifespan of the laser system. Therefore, there is an urgent need to research and develop a narrow-linewidth blue laser with high energy, high beam quality, and high stability to achieve better application results. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of existing blue pulsed lasers, such as large linewidth, low energy, poor beam quality, and poor stability, and to provide a narrow linewidth blue pulsed laser that improves the output energy and system stability of blue pulsed lasers, making it more suitable for applications with high requirements for linewidth, energy, and stability.
[0005] Basic principles
[0006] A 1μm single-frequency pulsed seed laser is amplified and frequency-doubled to generate a 0.5μm pulsed laser. The 0.5μm pulsed laser is used to pump the OPO, and a dual-crystal non-planar image-rotating ring cavity design is adopted for the OPO cavity. This allows the image plane to rotate 90° when the OPO signal beam travels through the cavity once. After multiple cyclic oscillations, spatial coherence is established in both directions of the beam, achieving the purpose of homogenizing the beam spot and improving the beam quality. Combined with single-frequency seed injection technology, the linewidth of the 0.9μm signal light is narrowed. The 0.9μm signal light is frequency-doubled to obtain a high-energy, high-beam-quality, narrow-linewidth 0.47-0.49μm blue pulsed laser output.
[0007] The technical solution of the present invention is as follows:
[0008] A narrow-linewidth blue pulsed laser is characterized by comprising five parts: a single-frequency pulsed laser module, a first frequency-doubling module, a single-frequency continuous seed laser module, an image-rotating optical parametric oscillation (OPO) module, and a second frequency-doubling module. A 1μm single-frequency pulsed seed laser is amplified and frequency-doubled to generate a 0.5μm pulsed laser. This 0.5μm pulsed laser is used to pump the OPO (Optical Point Oscillator). The OPO cavity employs a dual-crystal non-planar image-rotating ring cavity design, causing the image plane to rotate 90° during one revolution of the OPO signal beam within the cavity. Through multiple cyclic oscillations, spatial coherence is established in both directions of the beam. The specific structure is as follows:
[0009] The single-frequency pulsed laser module includes a pulsed seed laser for generating a single-frequency pulsed seed laser. The single-frequency pulsed seed laser is amplified sequentially by a laser pre-amplification module and a laser main amplification module to form a first fundamental frequency laser. The first fundamental frequency laser is polarized and output after being adjusted by a first half-wave plate.
[0010] The first frequency doubling module is used to receive the first fundamental frequency laser and generate the first frequency doubling laser. The first fundamental frequency laser is incident on the first frequency doubling module via the first frequency doubling crystal and undergoes frequency conversion. A portion of the first fundamental frequency laser is converted into the first frequency doubling laser, and the remaining first fundamental frequency laser is transmitted and output through the first beam splitter. The first frequency doubling laser is reflected by the first beam splitter to the second half-wave plate. After the polarization state is adjusted by the second half-wave plate, it is reflected and output by the first mirror to form parametric pump light.
[0011] The single-frequency continuous seed laser module includes a continuous seed laser, a coupling lens group, an optical isolator group, a third half-wave plate, and a second reflecting mirror. The continuous seed laser is used to generate a single-frequency continuous seed laser, which passes through the coupling lens group, the optical isolator group, and the third half-wave plate in sequence and is then reflected and output by the second reflecting mirror.
[0012] The aforementioned rotating optical parametric oscillator module comprises an optical parametric oscillator, a second beam splitter, and a sixth half-wave plate. The optical parametric oscillator is composed of a first parametric cavity mirror, a first parametric crystal, a second parametric cavity mirror, a fourth half-wave plate, a third parametric cavity mirror, a second parametric crystal, a fourth parametric cavity mirror, and a fifth half-wave plate. The first parametric crystal is disposed between the first and second parametric cavity mirrors. The fourth half-wave plate is disposed between the second and third parametric cavity mirrors. The second parametric crystal is disposed between the third and fourth parametric cavity mirrors. The fifth half-wave plate is disposed between the fourth and first parametric cavity mirrors.
[0013] The parametric pump light is incident on the optical parametric oscillator via the first parametric cavity mirror, and is converted by the first parametric crystal to generate the first signal light and the first idler light. The remaining parametric pump light passes sequentially through the second parametric cavity mirror, the fourth half-wave plate and the third parametric cavity mirror before being incident on the second parametric crystal. The second parametric crystal is converted to generate the second signal light and the second idler light. The remaining parametric pump light is transmitted and output through the fourth parametric cavity mirror.
[0014] The first signal light generated by the first parametric crystal and the second signal light generated by the second parametric crystal are partially reflected and partially transmitted by the second parametric cavity mirror. The partially reflected light serves as the resonant signal light of the optical parametric oscillator, which oscillates cyclically within the optical parametric oscillator. The partially transmitted light serves as the output signal light of the optical parametric oscillator, which is transmitted through the second beam splitter and its polarization state is adjusted by the sixth half-wave plate before being output to form the second fundamental frequency laser.
[0015] The first idler light generated by the first parametric crystal is transmitted through the second parametric cavity mirror to the second beam splitter, and is reflected by the second beam splitter; the second idler light generated by the second parametric crystal is transmitted through the fourth parametric cavity mirror.
[0016] The second frequency doubling module is used to receive the second fundamental frequency laser and generate the second frequency doubling laser. The second fundamental frequency laser is incident on the second frequency doubling module through the second frequency doubling crystal and undergoes frequency conversion. A portion of the second fundamental frequency laser is converted into the second frequency doubling laser, and the remaining second fundamental frequency laser is reflected and output through the third beam splitter. The second frequency doubling laser is transmitted and output through the third beam splitter. The second frequency doubling laser is a narrow linewidth blue pulse laser.
[0017] The optical parametric oscillator has a four-mirror non-planar rotating ring cavity structure. The planes formed by the reflection of the resonant signal light between the adjacent first, second, third, and fourth parametric cavity mirrors are not coplanar. The optical path between the first and second parametric cavity mirrors is L1, the optical path between the second and third parametric cavity mirrors is L2, the optical path between the third and fourth parametric cavity mirrors is L3, and the optical path between the third and fourth parametric cavity mirrors is L4. The length ratio of L1 to L2 satisfies: L1L2=2, and L1=L3, L2=L4.
[0018] The first parametric endoscope is coated with a 0.5μm antireflection film and a 0.9μm high reflectivity film; the second parametric endoscope is coated with a 0.5μm high reflectivity film, a 1.1-1.2μm antireflection film, and a 0.9μm dielectric film with 30%-50% transmittance; the third parametric endoscope is coated with 0.5μm and 0.9μm high reflectivity films; the fourth parametric endoscope is coated with 0.5μm and 1.1-1.2μm antireflection films, and a 0.9μm high reflectivity film; the coating angle of the first, second, third, and fourth parametric endoscopes is 32.8°.
[0019] The first half-wave plate is a 1μm half-wave plate; the second half-wave plate is a 0.5μm half-wave plate; the fourth half-wave plate is a dual-wavelength half-wave plate with 0.5μm and 0.9μm; and the third, fifth, and sixth half-wave plates are 0.9μm half-wave plates.
[0020] The first beam splitter is coated with a 1μm antireflection film at 45° and a 0.5μm high reflectivity film; the second beam splitter is coated with a 0.9μm antireflection film at 45° and a 1.1-1.2μm high reflectivity film; the third beam splitter is coated with a 0.47-0.49μm antireflection film at 45° and a 0.9μm high reflectivity film.
[0021] The first frequency doubling crystal is a type I phase-matched lithium triborate (LBO) crystal or a barium metaborate (β-BBO) crystal; the first parametric crystal and the second parametric crystal are type II phase-matched potassium titanate oxygenate (KTA) crystals or type I phase-matched potassium titanate oxygenate (KTP) crystals; the second frequency doubling crystal is a type I phase-matched barium metaborate (β-BBO) crystal or a bismuth borate (BIBO) crystal.
[0022] The pulsed seed laser outputs a single-frequency laser with a wavelength of 1 μm, a linear polarization state, and a pulse width of 1–100 ns.
[0023] The continuous seed laser is a single-frequency continuous laser with an output wavelength of 0.9 μm and a linear polarization state.
[0024] The laser pre-amplification module includes a pre-amplification crystal and a pump source, wherein the pre-amplification crystal is an Nd:YVO4 crystal or an Nd:YAG crystal;
[0025] The laser main amplification module (1-3) includes a main amplification crystal and a pump source, wherein the main amplification crystal is an Nd:YAG crystal.
[0026] The technical effects of this invention are as follows:
[0027] Compared with existing technologies, this invention uses a 0.5μm wavelength laser as the pump source of the optical parametric oscillator (OPO), avoiding the use of ultraviolet lasers in the laser system and improving system stability and reliability. This invention adopts a single-frequency seed injection and a dual-crystal non-planar image rotating ring cavity (OPO) design, which narrows the OPO output linewidth and reduces the OPO oscillation threshold, improving beam quality and conversion efficiency. Furthermore, high-energy, narrow-linewidth blue pulse laser output can be obtained through frequency doubling, making it suitable for fields such as marine resource exploration, underwater laser communication, bioengineering, and spectral analysis. Attached Figure Description
[0028] Figure 1 This is a schematic diagram of the narrow linewidth blue pulse laser structure of the present invention;
[0029] Figure 2 This is a schematic diagram of the three-dimensional structure of the non-planar rotating annular cavity of the present invention. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the technology of the present invention will be further described below in conjunction with the embodiments and accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.
[0031] Example
[0032] Figure 1 This is a schematic diagram of the narrow linewidth blue pulsed laser of the present invention, as shown below. Figure 1 As shown, the narrow linewidth blue pulsed laser of the present invention comprises five parts: a single-frequency pulsed laser module 1, a first frequency doubling module 2, a single-frequency continuous seed laser module 3, an image-rotating optical parametric oscillation module 4, and a second frequency doubling module 5.
[0033] The single-frequency pulsed laser module 1 generates a 1064.4nm pulsed laser and is incident on the first frequency doubling module 2. After receiving the 1064.4nm pulsed laser, the first frequency doubling module 2 generates a 532.2nm pulsed laser through frequency doubling conversion. The single-frequency continuous seed laser module 3 generates a 972.2nm single-frequency continuous seed laser. The image rotating optical parametric oscillation module 4 receives the 532.2nm pulsed laser and the 972.2nm single-frequency continuous seed laser and generates a 972.2nm narrow-linewidth pulsed laser through parametric conversion. The second frequency doubling module 5 receives the 972.2nm narrow-linewidth pulsed laser and generates a 486.1nm narrow-linewidth pulsed laser through frequency doubling.
[0034] In this embodiment, to obtain high-energy target narrow-linewidth blue pulsed laser output, the single-frequency pulsed laser module 1 includes a single-frequency pulsed laser seed laser 1-1, which generates a μJ-level 1064.4nm single-frequency pulsed laser seed laser. After being amplified by the laser pre-amplification module 1-2, it generates a mJ-level pulsed laser. After being amplified by the laser main amplification module 1-3, it generates a hundred-mJ-level pulsed laser. The hundred-mJ-level pulsed laser is polarized and output by the first half-wave plate 1-4. Preferably, the pulsed seed laser 1-1 outputs a single-frequency laser wavelength of 1064.4 nm, a linearly polarized laser state, and a pulse width of 10 ns; the laser pre-amplification module 1-2 includes a pre-amplification crystal and a pump source, wherein the pre-amplification crystal is an Nd:YVO4 crystal; the laser main amplification module 1-3 includes a main amplification crystal and a pump source, wherein the main amplification crystal is an Nd:YAG crystal; and the first half-wave plate 1-4 is a 1064.4 nm half-wave plate with a 1064.4 nm anti-reflection coating deposited on its surface.
[0035] In this embodiment, the 1064.4nm single-frequency pulsed laser is used as the first fundamental frequency laser. It is incident on the first frequency doubling module 2 by the first frequency doubling crystal 2-1 and undergoes frequency conversion. A portion of the first fundamental frequency laser is converted into a 532.2nm first frequency doubling laser. The remaining first fundamental frequency laser is transmitted and output through the first beam splitter 2-2. The first frequency doubling laser is reflected by the first beam splitter 2-2 to the second half-wave plate 2-3. After the polarization state is adjusted by the second half-wave plate 2-3, it is reflected and output by the first reflecting mirror 2-4 to form parametric pump light. The parametric pump light is a 532.2nm single-frequency pulsed laser in the hundreds of mJ range. Preferably, the first frequency doubling crystal 2-1 consists of two lithium triborate (LBO) crystals placed with walk-off compensation. The crystals employ type I critical phase matching, with cutting angles of θ = 90.0° and φ = 11.3°. The crystal end faces are coated with antireflection films of 1064.4 nm and 532.2 nm. The second half-wave plate 2-3 is a 532.2 nm half-wave plate with an antireflection film of 532.2 nm on its surface.
[0036] In this embodiment, to obtain the target narrow linewidth blue laser output, the single-frequency continuous seed laser module 3 includes a continuous seed laser 3-1, which is a single-frequency continuous laser. The output single-frequency continuous seed laser in the hundreds of mW range is collimated by a coupling lens group 3-2, isolated by an optical isolator group 3-3, and its polarization state is adjusted by a third half-wave plate 3-4. It is then reflected by a second reflecting mirror 3-5 and output, and the incident image is rotated by a second parametric cavity mirror 403 to form a parametric oscillation module 4. Preferably, the wavelength of the single-frequency continuous laser output by the continuous seed laser 3-1 is 972.2 nm, and the laser polarization state is linearly polarized. The third half-wave plate 3-4 is a 972.2 nm half-wave plate with a 972.2 nm anti-reflection coating on its surface.
[0037] In this embodiment, to obtain high-efficiency, high-beam-quality, narrow-linewidth blue laser output, the image-rotating optical parametric oscillation module 4 includes an optical parametric oscillator 4-1, a second beam splitter 4-2, and a sixth half-wave plate 4-3. The optical parametric oscillator 4-1 includes a first parametric cavity mirror 401, a first parametric crystal 402, a second parametric cavity mirror 403, a fourth half-wave plate 404, a third parametric cavity mirror 405, a second parametric crystal 406, a fourth parametric cavity mirror 407, and a fifth half-wave plate 408. 8; The first parametric crystal 402 is disposed in the middle of the continuous line between the first parametric cavity mirror 401 and the second parametric cavity mirror 403; the fourth half-wave plate 404 is disposed in the middle of the continuous line between the second parametric cavity mirror 403 and the third parametric cavity mirror 405; the second parametric crystal 406 is disposed in the middle of the continuous line between the third parametric cavity mirror 405 and the fourth parametric cavity mirror 407; and the fifth half-wave plate 408 is disposed in the middle of the continuous line between the fourth parametric cavity mirror 407 and the first parametric cavity mirror 401.
[0038] Preferably, the optical parametric oscillator 4 in this embodiment is a non-planar image rotating ring cavity structure, and its three-dimensional structure is as follows: Figure 2 As shown, the optical parametric oscillator 4 has a four-mirror non-planar image rotating ring cavity structure. The planes formed by the reflection of the resonant signal light between adjacent parametric cavity mirrors are not coplanar. The optical path between the first parametric cavity mirror 401 and the second parametric cavity mirror 403 is L1, the optical path between the second parametric cavity mirror 403 and the third parametric cavity mirror 405 is L2, the optical path between the second parametric cavity mirror 403 and the third parametric cavity mirror 405 is L3, and the optical path between the third parametric cavity mirror 405 and the fourth parametric cavity mirror 407 is L4. Let L1 = L3 = 44 mm and L2 = L4 = 31 mm, then the length ratio of L1 to L2 satisfies: L1L2 = 2.
[0039] The first parametric cavity mirror 401 is coated with a 32.8° antireflection coating for a wavelength of 532.2nm and a 32.8° high reflectivity coating for a wavelength of 972.2nm; the second parametric cavity mirror 403 is coated with a 32.8° high reflectivity coating for a wavelength of 532.2nm, a 32.8° antireflection coating for a wavelength of 1175.9nm, and a 32.8° dielectric film with a transmittance of 30% to 50% for a wavelength of 972.2nm; the third parametric cavity mirror 405 is coated with 32.8° high reflectivity coatings for wavelengths of 532.2nm and 972.2nm; and the fourth parametric cavity mirror 407 is coated with 32.8° antireflection coatings for lasers with wavelengths of 532.2nm and 1175.9nm, and a 32.8° high reflectivity coating for lasers with a wavelength of 972.2nm.
[0040] The first parametric crystal 402 and the second parametric crystal 406 are two types of critical phase-matched potassium titanate oxyarsenate (KTA) crystals. The crystal cutting angles are θ = 90.0° and φ = 28.0°. The crystal end faces are coated with antireflective films with wavelengths of 532.2nm, 972.2nm, and 1175.9nm.
[0041] The fourth half-wave plate 404 is a dual-wavelength half-wave plate with wavelengths of 532.2nm and 972.2nm, and its surface is coated with a 0° anti-reflection film with wavelengths of 532.2nm and 972.2nm; the fifth half-wave plate 408 and the sixth half-wave plate 4-3 are 972.2nm half-wave plates, and their surfaces are coated with an anti-reflection film with a wavelength of 972.2nm.
[0042] In this embodiment, the rotating optical parametric oscillator module 4 is used to receive the parametric pump light and the single-frequency continuous seed laser. The parametric pump light is incident on the parametric oscillator 4-1 via the first parametric cavity mirror 401, and after being converted by the first parametric crystal 402, it generates a first signal light of 972.2nm and a first idler light of 1175.9nm. The remaining parametric pump light is reflected sequentially by the second parametric cavity mirror 403, and then its polarization state is rotated by 45° by the fourth half-wave plate 404 and reflected by the third parametric cavity mirror 405, so that the polarization state in the optical path L3 is consistent with the polarization state in the optical path L1. Subsequently, it is incident on the second parametric crystal 406 to generate parametric gain, and after being converted by the second parametric crystal 406, it generates a second signal light of 972.2nm and a second idler light of 1175.9nm. The remaining parametric pump light is transmitted and output by the fourth parametric cavity mirror 407.
[0043] In this embodiment, the first signal light generated by the first parametric crystal 402 and the second signal light generated by the second parametric crystal 406 are partially reflected and partially transmitted by the second parametric cavity mirror 403. The partially reflected light serves as the resonant signal light of the optical parametric oscillator 4-1, which oscillates cyclically within the optical parametric oscillator 4-1. The fourth half-wave plate 404 and the fifth half-wave plate 408 keep its polarization direction consistent in the optical path L1. The partially transmitted light serves as the output signal light of the optical parametric oscillator 4-1. After being transmitted through the second beam splitter 4-2 and having its polarization state adjusted by the sixth half-wave plate 4-3, it is output to form the second fundamental frequency laser. The second fundamental frequency laser is a 972.2nm narrow linewidth pulse laser in the tens of mJ range.
[0044] The first idler light generated by the first parametric crystal 402 is transmitted through the second parametric cavity mirror 403 to the second beam splitter 4-2 and reflected out by the second beam splitter 4-2. The second idler light generated by the second parametric crystal 406 is transmitted out by the fourth parametric cavity mirror 407.
[0045] In this embodiment, the second frequency doubling module 5 is used to receive the second fundamental frequency laser and generate the second frequency doubling laser. The second fundamental frequency laser is incident on the second frequency doubling module 5 through the second frequency doubling crystal 5-1 and undergoes frequency conversion. A portion of the second fundamental frequency laser is converted into a 486.1nm second frequency doubling laser, and the remaining second fundamental frequency laser is reflected and output through the third beam splitter 5-2. The second frequency doubling laser is transmitted and output through the third beam splitter 5-2. The second frequency doubling laser is a 486.1nm narrow linewidth pulse laser in the tens of mJ range.
[0046] Preferably, the second frequency doubling crystal 5-1 is a type I phase-matched barium metaborate β-BBO crystal with a crystal cutting angle of θ = 163.2° and φ = 90.0°, and the crystal end face is coated with a 0° antireflection film for 972.2nm and 486.1nm wavelength lasers.
[0047] Experiments show that this invention, based on a 1μm pulsed laser, obtains a 0.5μm wavelength laser through frequency doubling and uses the 0.5μm wavelength laser as the pump source of the optical parametric oscillator (OPO), avoiding the use of ultraviolet lasers in the laser system, thus improving system stability and reliability. It employs single-frequency seed injection and a dual-crystal non-planar image rotating ring cavity (OPO) design to narrow the OPO output linewidth and reduce the OPO oscillation threshold, improving beam quality and conversion efficiency. Furthermore, it achieves a narrow-linewidth blue pulsed laser output of 0.47-0.49μm through frequency doubling, possessing advantages such as high energy, high beam quality, narrow linewidth, and high stability. This blue light band falls within the ocean transmission window, particularly covering the Fraunhofer dark line (486.1nm) of the solar radiation spectrum, exhibiting advantages such as low absorption loss and high signal-to-noise ratio. This invention is of great significance for improving the performance of spaceborne and airborne marine detection radars and underwater laser communication systems.
[0048] The embodiments described herein are merely illustrative of the technical features of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this invention should be included within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.
Claims
1. A narrow-linewidth blue pulsed laser, characterized in that, It consists of five parts: a single-frequency pulsed laser module (1), a first frequency doubling module (2), a single-frequency continuous seed laser module (3), an image-rotating optical parametric oscillator module (4), and a second frequency doubling module (5). The 1 μm single-frequency pulsed seed laser is amplified and frequency-doubled to generate a 0.5 μm pulsed laser. The 0.5 μm pulsed laser is used to pump the optical parametric oscillator (OPO). The 0.9 μm single-frequency continuous seed laser is injected to narrow the OPO output linewidth. The OPO cavity adopts a dual-crystal non-planar image-rotating ring cavity design, so that the image plane rotates 90° when the OPO signal beam is transmitted in the cavity for one revolution. After multiple cycles of oscillation, spatial coherence is established in two directions of the beam, which improves the beam quality and conversion efficiency when the OPO outputs high energy. The single-frequency pulsed laser module (1) includes a pulsed seed laser (1-1) for generating a 1 μm single-frequency pulsed seed laser. The single-frequency pulsed seed laser is amplified sequentially by a laser pre-amplification module (1-2) and a laser main amplification module (1-3) to form a first fundamental frequency laser. The first fundamental frequency laser is polarized and output by a first half-wave plate (1-4). The first frequency doubling module (2) is used to receive the first fundamental frequency laser and generate the first frequency doubling laser. The first fundamental frequency laser is incident on the first frequency doubling module (2) through the first frequency doubling crystal (2-1) and undergoes frequency conversion. A portion of the first fundamental frequency laser is converted into the first frequency doubling laser, and the remaining first fundamental frequency laser is transmitted and output through the first beam splitter (2-2). The first frequency doubling laser is reflected by the first beam splitter (2-2) to the second half-wave plate (2-3). After the polarization state is adjusted by the second half-wave plate (2-3), it is reflected and output by the first reflector (2-4) to form parametric pump light. The parametric pump light is a 0.5 μm wavelength laser. The single-frequency continuous seed laser module (3) includes a continuous seed laser (3-1), a coupling lens group (3-2), an optical isolator group (3-3), a third half-wave plate (3-4), and a second reflecting mirror (3-5). The continuous seed laser (3-1) is used to generate a 0.9 μm single-frequency continuous seed laser. The single-frequency continuous seed laser passes through the coupling lens group (3-2), the optical isolator group (3-3), and the third half-wave plate (3-4) in sequence and is then reflected and output by the second reflecting mirror (3-5). The aforementioned rotating optical parametric oscillation module (4) includes an optical parametric oscillator (4-1), a second beam splitter (4-2), and a sixth half-wave plate (4-3). The optical parametric oscillator (4-1) is composed of a first parametric cavity mirror (401), a first parametric crystal (402), a second parametric cavity mirror (403), a fourth half-wave plate (404), a third parametric cavity mirror (405), a second parametric crystal (406), a fourth parametric cavity mirror (407), and a fifth half-wave plate (408). The first parametric crystal (402) is disposed between the first parametric cavity mirror (401) and the second parametric cavity mirror (403), the fourth half-wave plate (404) is disposed between the second parametric cavity mirror (403) and the third parametric cavity mirror (405), the second parametric crystal (406) is disposed between the third parametric cavity mirror (405) and the fourth parametric cavity mirror (407), and the fifth half-wave plate (408) is disposed between the fourth parametric cavity mirror (407) and the first parametric cavity mirror (401). The parametric pump light is incident on the optical parametric oscillator (4-1) via the first parametric cavity mirror (401), and is converted by the first parametric crystal (402) to generate the first signal light and the first idler light. The remaining parametric pump light passes sequentially through the second parametric cavity mirror (403), the fourth half-wave plate (404) and the third parametric cavity mirror (405) before being incident on the second parametric crystal (406). The second parametric crystal (406) converts the light into the second signal light and the second idler light. The remaining parametric pump light is transmitted and output through the fourth parametric cavity mirror (407). The first signal light generated by the first parametric crystal (402) and the second signal light generated by the second parametric crystal (406) are partially reflected and partially transmitted by the second parametric cavity mirror (403). The partially reflected light serves as the resonant signal light of the optical parametric oscillator (4-1), which oscillates cyclically within the optical parametric oscillator (4-1). The partially transmitted light serves as the output signal light of the optical parametric oscillator (4-1), which is transmitted through the second beam splitter (4-2) and its polarization state is adjusted by the sixth half-wave plate (4-3) before being output to form the second fundamental frequency laser. The first idler light generated by the first parametric crystal (402) is transmitted through the second parametric cavity mirror (403) to the second beam splitter (4-2), and is reflected by the second beam splitter (4-2); the second idler light generated by the second parametric crystal (406) is transmitted through the fourth parametric cavity mirror (407). The second frequency doubling module (5) is used to receive the second fundamental frequency laser and generate the second frequency doubling laser. The second fundamental frequency laser is incident on the second frequency doubling module (5) through the second frequency doubling crystal (5-1) and undergoes frequency conversion. A portion of the second fundamental frequency laser is converted into the second frequency doubling laser, and the remaining second fundamental frequency laser is reflected and output through the third beam splitter (5-2). The second frequency doubling laser is transmitted and output through the third beam splitter (5-2). The second frequency doubling laser is a narrow linewidth blue pulse laser.
2. The narrow linewidth blue pulse laser according to claim 1, characterized in that, The optical parametric oscillator (4-1) has a four-mirror non-planar rotating ring cavity structure. The resonant signal light is reflected between adjacent first parametric cavity mirrors (401), second parametric cavity mirrors (403), third parametric cavity mirrors (405), and fourth parametric cavity mirrors (407), forming non-coplanar planes. The optical path between the first parametric cavity mirror (401) and the second parametric cavity mirror (403) is L1, the optical path between the second parametric cavity mirror (403) and the third parametric cavity mirror (405) is L2, the optical path between the third parametric cavity mirror (403) and the fourth parametric cavity mirror (405) is L3, and the optical path between the third parametric cavity mirror (405) and the fourth parametric cavity mirror (407) is L4. The length ratio of L1 to L2 satisfies: ,and , .
3. The narrow linewidth blue pulse laser according to claim 1, characterized in that, The first parametric endoscope (401) is coated with a 0.5 μm antireflection film and a 0.9 μm high reflectivity film; the second parametric endoscope (403) is coated with a 0.5 μm high reflectivity film, a 1.1-1.2 μm antireflection film, and a 0.9 μm 30%~50% transmittance dielectric film; the third parametric endoscope (405) is coated with 0.5 μm and 0.9 μm high reflectivity films; the fourth parametric endoscope (407) is coated with 0.5 μm and 1.1-1.2 μm antireflection films and a 0.9 μm high reflectivity film; the coating angle of the first parametric endoscope (401), the second parametric endoscope (403), the third parametric endoscope (405), and the fourth parametric endoscope (407) is 32.8°.
4. The narrow linewidth blue pulse laser according to claim 3, characterized in that, The first half-wave plate (1-4) is a 1 μm half-wave plate; the second half-wave plate (2-3) is a 0.5 μm half-wave plate; the fourth half-wave plate (404) is a dual-wave plate with wavelengths of 0.5 μm and 0.9 μm; and the third half-wave plate (3-4), the fifth half-wave plate (408), and the sixth half-wave plate (4-3) are 0.9 μm half-wave plates.
5. The narrow linewidth blue pulse laser according to claim 1, characterized in that, The first beam splitter (2-2) is coated with a 1 μm antireflection coating at 45° and a 0.5 μm high reflectivity coating; the second beam splitter (4-2) is coated with a 0.9 μm antireflection coating at 45° and a 1.1-1.2 μm high reflectivity coating; the third beam splitter (5-2) is coated with a 0.47-0.49 μm antireflection coating at 45° and a 0.9 μm high reflectivity coating.
6. The narrow linewidth blue pulse laser according to claim 1, characterized in that, The first frequency doubling crystal (2-1) is a type I phase-matched lithium triborate (LBO) crystal or a barium metaborate (β-BBO) crystal; the first parametric crystal (402) and the second parametric crystal (406) are type II phase-matched potassium titanate oxygenate (KTA) crystals or type I phase-matched potassium titanate oxygenate (KTP) crystals; the second frequency doubling crystal (5-1) is a type I phase-matched barium metaborate (β-BBO) crystal or a bismuth borate (BIBO) crystal.
7. The narrow linewidth blue pulse laser according to claim 1, characterized in that, The pulsed seed laser (1-1) outputs a single-frequency laser with a wavelength of 1 μm, a linear polarization state, and a pulse width of 1~100 ns; The continuous seed laser (3-1) is a single-frequency continuous laser with an output single-frequency laser wavelength of 0.9 μm and a linear polarization state.
8. The narrow linewidth blue pulse laser according to any one of claims 1 to 7, characterized in that, The laser pre-amplification module (1-2) includes a pre-amplification crystal and a pump source, wherein the pre-amplification crystal is an Nd:YVO4 crystal or an Nd:YAG crystal; The laser main amplification module (1-3) includes a main amplification crystal and a pump source, wherein the main amplification crystal is an Nd:YAG crystal.