Narrow linewidth intracavity raman laser

Abstract

A narrow-linewidth internal cavity Raman laser, belonging to the field of Raman lasers, is disclosed to address the problems existing in current Raman lasers. The invention includes a laser emitting section, an SRS effect cavity, a beam splitter, a pump beam splitter, and a Stokes beam splitter. The laser emitting section emits a first optical signal with a tunable first preset power and a first preset wavelength into the SRS effect cavity. The first optical signal is amplified in the SRS effect cavity to generate a second optical signal, wherein the first and second optical signals are pump lights with different powers and wavelengths. In the SRS effect cavity, the second optical signal is converted into Stokes light using stimulated Raman oscillation, leaving a portion of unconverted pump light. The Stokes light and the unconverted pump light are separated by the beam splitter, causing the Stokes light to oscillate in the seed beam oscillation cavity and the residual pump light from the stimulated Raman effect to oscillate in the pump beam oscillation cavity, thereby outputting a narrow-linewidth laser.

Description

Technical Field

[0001] This invention relates to a narrow-linewidth intracavity Raman laser with compressed linewidth within the cavity, belonging to the field of Raman lasers. Background Technology

[0002] Narrow-linewidth lasers possess characteristics such as high monochromaticity, high coherence, high beam quality, and extremely low phase noise, thus showing broad application prospects in laser communication, laser ranging, lidar, and laser cooling. With the development of nonlinear technology, the stimulated Raman (SRS) effect induced by molecular vibrations in Raman media has become an important means to achieve high-power laser output, frequency conversion, and beam purification. SRS-based Raman lasers have many advantages: extremely wide wavelength tunability, covering a broad wavelength range from ultraviolet to mid-infrared; filling output gaps in traditional population-inversion lasers; stable frequency shift, as the Raman frequency shift is only related to the lattice vibrations of the medium and is independent of the pump light frequency; and high conversion efficiency, as the gain of the Raman laser is proportional to the pump light intensity, with no saturation or spatial hole burning effects, enabling energy conversion close to the quantum efficiency limit. However, Raman lasers have relatively wide linewidths, requiring further spectral compression for application in narrow-linewidth laser fields. The following are current methods for obtaining narrow-linewidth lasers and their limiting factors:

[0003] One method involves adding beam-splitting devices, such as blazed gratings or volume Bragg gratings, outside the laser resonator to filter the beam generated by the resonator and compress the spectral lines. However, this method of obtaining narrow-linewidth lasers involves filtering the spectral lines of the output laser outside the resonator after it has been generated, which greatly reduces the output efficiency of the laser and makes it difficult to obtain high-power laser output.

[0004] Second: Using distributed feedback (DFB) or distributed Bragg reflector (DBR) structures in fiber lasers. In DFB or DBR fiber lasers, a periodic grating structure is incorporated into the fiber, providing the necessary wavelength-selective feedback for laser operation. This structure ensures the laser output is at a specific wavelength and has a narrow linewidth. However, the core diameter of this type of fiber laser is relatively small compared to other types of lasers, making it difficult to increase the output power without damaging the fiber; furthermore, high-power fiber lasers may be affected by nonlinear effects such as Raman scattering and self-phase modulation, making it difficult to produce high-power laser output.

[0005] Third: Adding a photoplethysmometer (FP) to the laser resonator for wavelength selection. However, this method requires extremely high precision from the FP, often requiring multiple FPs, which greatly increases the difficulty of implementation and also introduces insertion loss, reducing the laser's operating efficiency.

[0006] Researchers have achieved Raman laser output using straight-cavity and ring-cavity lasers. However, in traditional Raman lasers, the Stokes beam return and pump beam are difficult to separate, making it impossible to adjust the Stokes beam separately. This leads to a thermal lensing effect in the pump laser crystal during high-power operation, affecting the pump beam quality and further reducing the Stokes beam quality in the Raman cavity. This severely impacts the output beam quality and stability, significantly limiting the power increase of Raman lasers. Furthermore, there is a significant demand for narrow-linewidth, high-power, and wavelength-tunable lasers in space environment detection and laser industrial processing. However, traditional solid-state lasers struggle to simultaneously achieve narrow linewidth, high-power output, and wavelength tunability. Summary of the Invention

[0007] To address the problems of existing Raman lasers, this invention provides a narrow-linewidth internal cavity Raman laser, which achieves narrow linewidth, high conversion efficiency, and tunable wavelength, as detailed below:

[0008] The present invention discloses a narrow linewidth internal cavity Raman laser, comprising a laser emitting section, an SRS effect cavity, a beam splitter, a pump beam splitter, and a Stokes beam splitter; the pump beam splitter and the SRS effect cavity are coaxial and together constitute a pump beam oscillation cavity, and the Stokes beam splitter and the SRS effect cavity are at an angle to each other and together constitute a seed beam oscillation cavity.

[0009] The laser emitting unit is used to emit a first optical signal with a tunable first preset power and a first preset wavelength into the SRS effect cavity, and the first optical signal is amplified in the SRS effect cavity to generate a second optical signal. The first optical signal and the second optical signal are pump lights with different powers and wavelengths.

[0010] In the SRS effect cavity, the second optical signal is converted into Stokes light using the stimulated Raman effect, and a portion of unconverted pump light remains. The Stokes light and the unconverted pump light are separated by a beam splitter, so that the Stokes light oscillates in the seed light oscillation cavity, and the pump light remaining from the stimulated Raman effect oscillates in the pump light oscillation cavity.

[0011] The Stokes beam enters the Stokes beam splitter cavity and is diffracted by a second body Bragg grating set inside the cavity. The diffraction compresses the linewidth of the Stokes beam, thereby outputting a narrow linewidth laser.

[0012] The pump light that is not converted by the stimulated Raman effect enters the pump light beam splitter cavity and oscillates in the pump light oscillation cavity. The unconverted pump light is filtered and diffracted by the first volume Bragg grating set in the cavity, and the narrow-linewidth residual pump light obtained by diffraction is reflected back into the SRS effect cavity to realize the amplification of the narrow-linewidth second signal light.

[0013] The narrow-linewidth second optical signal again utilizes the stimulated Raman effect to generate narrow-linewidth Stokes light, and further compresses the linewidth through diffraction by the second volume Bragg grating.

[0014] Preferably, the laser emitting unit includes a pump source 1 and a focusing lens 2. The pump source 1 emits a first optical signal with a tunable first preset power and a first preset wavelength, which is then focused and output by the focusing lens 2.

[0015] Preferably, the beam splitter is implemented using a beam splitter 7.

[0016] Preferably, the SRS effect cavity is provided with an input mirror 3, a laser gain medium 4, a first shaping lens 5, and a diamond crystal 6. The first optical signal output from the pump source 1 is focused by the focusing lens 2 and then enters the laser gain medium 4 through the input mirror 3, where it is amplified to generate a second optical signal. The second optical signal is shaped by the first shaping lens 5 and then enters the diamond crystal 6 to generate stimulated Raman effect, thus generating Stokes light. The laser gain medium 4 is an Nd:YAG crystal, and the diamond crystal 6 is an Nd:YAG crystal. <110> The artificial diamond crystal is cut from an axial diameter, and the beam splitter 7 is a plane mirror.

[0017] Preferably, the SRS effect cavity is equipped with an input mirror 3, a Brewster-cut crystal 16, a first shaping lens 5, and a diamond crystal 6. The first optical signal output from the pump source 1 is focused by the focusing lens 2 and then enters the Brewster-cut crystal 16 via the input mirror 3. The Brewster-cut crystal 16 filters out the pump light whose polarization direction is perpendicular to the incident plane, retains the pump light whose polarization direction is parallel to the incident plane, and generates a second optical signal after gaining. The second optical signal is shaped by the first shaping lens 5 and then enters the diamond crystal 6 to generate stimulated Raman effect, exciting the generation of Stokes light. The diamond crystal 6 is a cross-section of the surface. <110> The artificial diamond crystal is axially cut. The beam splitter 7 is a plane mirror. The Brewster-cut crystal 16 is a Brewster-cut Nd:YVO4 crystal. The left end face of the Brewster-cut crystal 16 is a straight face, and the right end face of the Brewster-cut crystal 16 is a beveled face.

[0018] Preferably, a second shaping lens 8 and a first volume Bragg grating 9 are disposed in the pump light beam splitter cavity, and a third shaping lens 10 and a second volume Bragg grating 11 are disposed in the Stokes beam splitter cavity;

[0019] The residual unconverted pump light is transmitted through the beam splitter 7, then shaped by the second shaping lens 8, and then diffracted by the first volume Bragg grating 9. The narrow-linewidth residual pump light obtained by diffraction is reflected back to the gain component in the SRS effect cavity to amplify the narrow-linewidth second optical signal.

[0020] After being reflected by the beam splitter 7, the Stokes light enters the third shaping lens 10 for shaping, and then enters the second body Bragg grating 11 for diffraction, outputting a stable narrow linewidth laser.

[0021] Preferably, it also includes a first heating patch element 12, a second heating patch element 13, a first DC power supply 14, and a second DC power supply 15. The first heating patch element 12 is attached to the lower surface of the first bulk Bragg grating 9 with silicone grease. The first DC power supply 14 is used to set a specific voltage to heat the first bulk Bragg grating 9 to a specific temperature, thereby changing the center wavelength of the first bulk Bragg grating 9 to achieve the diffraction screening effect on the residual unconverted pump light.

[0022] The second heating patch element 13 is attached to the lower surface of the second bulk Bragg grating 11 with silicone grease. A specific voltage is set by the second DC power supply 15 to heat the second bulk Bragg grating 11 to a specific temperature, thereby changing the center wavelength of the second bulk Bragg grating 11 to achieve the diffraction and filtering effect of the Stokes light.

[0023] Preferably, the angle between the normal direction of the beam splitter surface and the optical axis of the SRS effect cavity is 10°.

[0024] This invention provides a narrow-linewidth internal cavity Raman laser, with the following advantages:

[0025] 1. This invention uses a volume Bragg grating inside the cavity instead of a traditional reflector as the output mirror, in order to compress the spectral linewidth of the pump light and Stokes light while maximizing the gain efficiency of the laser, thereby obtaining a narrow linewidth, high-power laser output.

[0026] 2. This invention utilizes a volume Bragg grating as the output mirror. The center wavelength of the volume Bragg grating can be changed by adjusting its temperature. By setting a certain angle, a specific diffraction efficiency can be achieved for lasers of a specific wavelength, thereby achieving selectivity for different wavelengths of light and thus realizing the characteristic of tunable output wavelength.

[0027] 3. This invention provides a composite resonant cavity. Through the design of an intracavity beam splitter, the pump light and Stokes light are separated at the beam splitter. The pump light oscillates and is amplified in a pump light oscillation cavity with a straight cavity structure, while the Stokes light oscillates and is amplified in a seed light oscillation cavity with a bent structure. The positions of the shaping lenses in the two cavities can be adjusted separately to achieve fine control of the output light power and beam quality, facilitating compensation for the thermal lensing effect generated by the laser crystal at high power, thereby achieving stable output at high power. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the narrow linewidth internal cavity Raman laser structure described in Example 1;

[0029] Figure 2 This is a schematic diagram of the wavelength-tunable narrow-linewidth internal cavity Raman laser structure described in Example 2;

[0030] Figure 3 This is a schematic diagram of the wavelength-tunable linearly polarized narrow-linewidth internal cavity Raman laser structure described in Example 3;

[0031] The attached diagram lists the components represented by each number as follows:

[0032] 1: Pump source; 2: Focusing lens;

[0033] 3: Input mirror; 4: Laser gain medium;

[0034] 5: First shaping lens; 6: Diamond crystal;

[0035] 7: Beam splitter; 8: Second shaping lens;

[0036] 9: First-volume Bragg grating; 10: Third-stage shaping lens;

[0037] 11: Second-body Bragg grating; 12: First heating patch element;

[0038] 13: Second heating element; 14: First DC power supply;

[0039] 15: Second DC power supply; 16: Brewster-cut crystal;

[0040] θ1: The angle between the normal direction of the beam splitter surface and the optical axis of the SRS effect cavity;

[0041] θ2: The angle between the normal direction of the second-body Bragg grating surface and the optical axis of the Stokes beam splitter.

[0042] L1: Distance between the input mirror and the left end face of the laser gain medium;

[0043] L2: The distance between the right end face of the laser gain medium and the first shaping lens;

[0044] L3: The distance between the first shaping lens and the left end face of the diamond crystal;

[0045] L4: The distance between the right end face of the diamond crystal and the beam splitter;

[0046] L5: The distance between the beam splitter and the second shaping lens;

[0047] L6: The distance between the second shaping lens and the first volume Bragg grating;

[0048] L7: Distance between the beam splitter and the third shaping lens;

[0049] L8: The distance between the third shaping lens and the second volume Bragg grating;

[0050] L9: The distance between the input mirror and the intersection of the left end face of the Brewster-cut crystal and the optical axis;

[0051] L10: The distance between the intersection of the right end face of the Brewster-cut crystal and the optical axis and the first shaping lens. Detailed Implementation

[0052] 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.

[0053] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0054] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0055] Compared to methods that compress linewidth in the external cavity, this invention uses a high-diffraction-efficiency bulk Bragg grating within the cavity to compress the spectral lines of the pump and Stokes beams, significantly improving the laser's energy conversion efficiency and beam quality. Furthermore, when changing the pump beam, the output wavelength of the resonant cavity can be adjusted simply by setting the bulk Bragg grating to a specific temperature. In addition, unlike traditional standing-wave cavity Raman lasers, this invention employs a composite cavity structure, easily separating the Stokes and pump beams at the beam splitter. The Stokes beam oscillates in a seed beam oscillation cavity with a bent structure, while the pump beam oscillates in a pump beam oscillation cavity with a straight cavity structure. The pump and Stokes beams can be adjusted separately using shaping lenses, reducing mutual interference between beams of different wavelengths and increasing the stability of the resonant cavity. Moreover, the composite cavity structure creates two optical waists within the cavity, allowing the laser gain medium and diamond crystal to be independently placed at different optical waists, achieving parameter matching, increasing conversion efficiency, and making the laser more compact and easier to engineer. Meanwhile, the use of diamond crystal, which has extremely high thermal conductivity, extremely wide spectral transmittance, and extremely large Raman frequency shift, as a nonlinear crystal enables the laser to withstand higher pump power, which is beneficial for obtaining high-power laser output.

[0056] In summary, the Raman laser proposed in this invention, which utilizes a volume Bragg grating for spectral line compression within the cavity, is an effective approach to achieving a narrow-linewidth, high-power, and wavelength-tunable laser, and is of great significance to the development of space exploration, laser communication, and laser industrial processing.

[0057] The narrow linewidth internal cavity Raman laser of the present invention includes a laser emitting section, an SRS effect cavity, a beam splitter, a pump beam splitter and a Stokes beam splitter; the pump beam splitter and the SRS effect cavity are coaxial and together constitute a pump beam oscillation cavity, and the Stokes beam splitter and the SRS effect cavity are at an angle to each other and together constitute a seed beam oscillation cavity.

[0058] The laser emitting unit is used to emit a first optical signal with a tunable first preset power and a first preset wavelength into the SRS effect cavity, and the first optical signal is amplified in the SRS effect cavity to generate a second optical signal. The first optical signal and the second optical signal are pump lights with different powers and wavelengths.

[0059] In the SRS effect cavity, the second optical signal is converted into Stokes light using the stimulated Raman effect, and a portion of unconverted pump light remains. The Stokes light and the unconverted pump light are separated by a beam splitter, so that the Stokes light oscillates in the seed light oscillation cavity, and the pump light remaining from the stimulated Raman effect oscillates in the pump light oscillation cavity.

[0060] The Stokes beam enters the Stokes beam splitter cavity and is diffracted by a second body Bragg grating set inside the cavity. The diffraction compresses the linewidth of the Stokes beam, thereby outputting a narrow linewidth laser.

[0061] The pump light that is not converted by the stimulated Raman effect enters the pump light beam splitter cavity and oscillates in the pump light oscillation cavity. The unconverted pump light is filtered and diffracted by the first volume Bragg grating set in the cavity, and the narrow-linewidth residual pump light obtained by diffraction is reflected back into the SRS effect cavity to realize the amplification of the narrow-linewidth second signal light.

[0062] The narrow-linewidth second optical signal again utilizes the stimulated Raman effect to generate narrow-linewidth Stokes light, and further compresses the linewidth through diffraction by the second volume Bragg grating.

[0063] The laser emitting unit includes a pump source 1 and a focusing lens 2. The pump source 1 emits a first optical signal with a tunable first preset power and a first preset wavelength, which is then focused and output by the focusing lens 2.

[0064] The beam splitter is implemented using a beam splitter 7. The angle between the beam splitter 7 and the optical axis of the SRS effect cavity is θ1.

[0065] The present invention will be specifically described below with reference to three embodiments.

[0066] Example 1

[0067] See Figure 1 A narrow linewidth internal cavity Raman laser includes: a pump source 1, a focusing lens 2, an input mirror 3, a laser gain medium 4, a first shaping lens 5, a diamond crystal 6, a beam splitter 7, a second shaping lens 8, a first volume Bragg grating 9, a third shaping lens 10, and a second volume Bragg grating 11.

[0068] The composite resonant cavity provided in this embodiment includes a straight cavity and a V-shaped cavity. The straight cavity is composed of a pump beam splitter cavity and an SRS effect cavity with coaxial optical axes, and the V-shaped cavity is composed of a Stokes beam splitter cavity with optical axes at an angle and an SRS effect cavity.

[0069] Pump source 1 outputs pump light with a wavelength of 808nm; focusing lens 2 is a convex lens with a radius of curvature of 50mm, coated on both sides with a broadband dielectric film that enhances the reflection of the pump light wavelength of 808nm; input mirror 3 is a plano-concave mirror with a radius of curvature of 75mm, coated on both sides with a broadband dielectric film that enhances the reflection of 808nm, and the concave side is coated with a broadband dielectric film with a reflectivity >99.8% for pump light at 1064nm and Stokes light at 1240nm; laser gain medium 4 is an Nd:YAG crystal, coated on both sides with a broadband dielectric film that enhances the reflection of pump light at 808nm, pump light at 1064nm, and Stokes light at 1240nm; first shaping lens 5 is a convex lens with a radius of curvature of 100mm, coated on both sides with a broadband dielectric film that enhances the reflection of pump light at 1064nm and Stokes light at 1240nm; diamond crystal 6 is a... <110> Axially cut synthetic diamond crystal, measuring 7×4×1.2mm. 3 The first beam splitter 7 is a plane mirror, coated on both sides with a broadband dielectric film that enhances the transmission of pump light at 1064nm and Stokes light at 1240nm, and a broadband dielectric film with a reflectivity >99.8% for Stokes light at 1240nm. The angle θ1 between the normal direction of the beam splitter 7 and the incident pump light is 10°. The second shaping lens 8 is a convex lens with a radius of curvature of 100mm, coated on both sides with a broadband dielectric film that enhances the transmission of pump light at 1064nm. The first bulk Bragg grating 9 is a bulk grating with a center wavelength of 1064nm and a diffraction efficiency of 99%. The first is a Bragg grating with a wideband dielectric film coated on its surface to enhance the light transmission at 1064 nm. The surface normal is parallel to the pump light direction, resulting in a diffraction efficiency of 99% for the pump light at 1064 nm within the cavity. The second is a convex lens with a radius of curvature of 100 mm, coated on both sides with a wideband dielectric film to enhance the light transmission at 1240 nm for Stokes light. The third is a volume Bragg grating with a center wavelength of 1240 nm and a diffraction efficiency of 99%. The surface is coated with a wideband dielectric film to enhance the light transmission at 1240 nm, and the angle between the surface normal and the Stokes light is θ2, resulting in a diffraction efficiency of 92%.

[0070] The distance between the input mirror 3 and the left end face of the laser gain medium 4 is L1 = 20 mm; the distance between the right end face of the gain medium 4 and the first shaping lens 5 is L2 = 20 mm; the distance between the first shaping lens 5 and the left end face of the diamond crystal 6 is L3 = 20 mm; the distance between the right end face of the diamond crystal 6 and the beam splitter 7 is L4 = 35 mm; the distance between the beam splitter 7 and the second shaping lens 8 is L5 = 60 mm; the distance between the second shaping lens 8 and the surface of the first bulk Bragg grating 9 is L6 = 30 mm; the distance between the beam splitter 7 and the third shaping lens 10 is L7 = 62 mm; and the distance between the third shaping lens 10 and the surface of the second bulk Bragg grating 11 is L8 = 30 mm.

[0071] The 808nm pump light generated by pump source 1 is focused onto the laser gain medium 4, i.e., the center of the Nd:YAG crystal, after passing through focusing lens 2 and input mirror 3. The radius of the 808nm pump light spot is 185μm. When the 808nm pump light is focused onto the end face of the Nd:YAG crystal, its energy is absorbed and transferred to neodymium ions (Nd) in the crystal. 3+ In Nd:YAG crystals, neodymium ions are excited to a higher energy level after absorbing energy. When the neodymium ions return from the higher energy level to a lower energy level, they generate a wavelength of 1064 nm and a frequency of ω. p The laser radiation is emitted. The 1064nm pump light, after passing through the first shaping lens 5, is focused at the center of the diamond crystal 6. The waist radius of this 1064nm pump beam is 73μm. The focused 1064nm pump light has improved efficiency and can more easily filter out non-target wavelengths. The frequency is ω. p The pump light excites the ground-state atoms of diamond crystal 6 to a virtual Raman upper level, simultaneously generating a frequency of ω. S Raman photons and a frequency of ω R The optical phonon, and satisfying ω p =ω S +ω R The Raman shift of diamond crystal 6 is 1332 cm⁻¹. -1 When the pump light wavelength is 1064 nm, the excited Stokes light wavelength is 1240 nm. The remaining unconverted 1064 nm pump light undergoes diffraction at the first body Bragg grating 9 after passing through the beam splitter 7 and the second shaping lens 8. This diffraction causes the 1064 nm pump light to oscillate and amplify in the straight cavity. The diffraction compresses the linewidth of the 1064 nm pump light, resulting in a narrower linewidth and increased energy density. Simultaneously, the 1240 nm Stokes light generated by the stimulated Raman effect oscillates in the V-shaped cavity and undergoes diffraction at the second body Bragg grating 11. This diffraction compresses the linewidth of the 1240 nm Stokes light, thus outputting a narrow-linewidth 1240 nm laser.

[0072] In summary, this invention proposes a narrow-linewidth intracavity Raman laser based on a combination of a V-cavity and a straight cavity. An 808nm laser output from a high-power pump source is coupled into the resonant cavity, exciting the Nd:YAG laser gain medium within the cavity to generate a 1064nm pump light. This 1064nm pump light is diffracted by a bulk Bragg grating within the straight cavity, resulting in linewidth compression and oscillation amplification. Simultaneously, the narrow-linewidth 1064nm pump light excites the stimulated Raman effect of a diamond crystal to generate 1240nm Stokes light. This light is then oscillated and amplified within the V-cavity by a beam splitter and diffracted by a bulk Bragg grating, resulting in linewidth compression. This achieves a narrow-linewidth, high-power 1240nm laser output.

[0073] Example 2

[0074] See Figure 2 A wavelength-tunable narrow-linewidth intracavity Raman laser includes: a pump source 1, a focusing lens 2, an input mirror 3, a laser gain medium 4, a first shaping lens 5, a diamond crystal 6, a beam splitter 7, a second shaping lens 8, a first bulk Bragg grating 9, a first heating patch element 12, a third shaping lens 10, a second bulk Bragg grating 11, a second heating patch element 13, a first DC power supply 14, and a second DC power supply 15.

[0075] The composite resonant cavity provided in this embodiment includes a straight cavity and a V-shaped cavity. The straight cavity is composed of a pump beam splitter cavity and an SRS effect cavity with coaxial optical axes, and the V-shaped cavity is composed of a Stokes beam splitter cavity with optical axes at an angle and an SRS effect cavity.

[0076] Pump source 1 outputs pump light with a wavelength of 808nm and a spectral linewidth of <1nm; focusing lens 2 is a convex lens with a radius of curvature of 50mm, coated on both sides with a broadband dielectric film that enhances the reflection of the pump wavelength of 808nm; input mirror 3 is a plano-concave mirror with a radius of curvature of 75mm, coated on both sides with a broadband dielectric film that enhances the reflection of 808nm, and the concave side is coated with a broadband dielectric film with a reflectivity >99.8% for 1064nm and Stokes light 1240nm; laser gain medium 4 is an Nd:YVO4 crystal, coated on both sides with a broadband dielectric film that enhances the reflection of pump light 808nm, pump light 1064nm and Stokes light 1240nm; first shaping lens 5 is a convex lens with a radius of curvature of 100mm, coated on both sides with a broadband dielectric film that enhances the reflection of pump light 1064nm and Stokes light 1240nm; diamond crystal 6 is a... <110> Axially cut synthetic diamond crystal, measuring 7×4×1.2mm. 3The first beam splitter 7 is a plane mirror, coated on both sides with a broadband dielectric film that enhances the transmission of pump light at 1064nm and Stokes light at 1240nm, and a broadband dielectric film with a reflectivity >99.8% for Stokes light at 1240nm. The angle θ1 between the normal direction of the beam splitter 7 surface and the incident pump light is 10°. The second shaping lens 8 is a convex lens with a radius of curvature of 100mm, coated on both sides with a broadband dielectric film that enhances the transmission of pump light at 1064nm. The first bulk... The bulk Bragg grating 9 is a bulk Bragg grating with a center wavelength of 1064nm and a diffraction efficiency of 99%. Its surface is coated with a broadband dielectric film that enhances the light transmission at 1064nm, and the surface normal is parallel to the pump light direction. A first heating element 12 is attached to the lower surface of the first bulk Bragg grating 9 using silicone grease. A first DC power supply 14 sets a voltage V1 to heat the first bulk Bragg grating 9 to a temperature T1, causing the center wavelength of the first bulk Bragg grating 9 to become λ1 = 1064nm + Δλ1 (Δλ1 is very small, ensuring sufficient diffraction efficiency at 1064nm). The broadband dielectric film, which is transparent, still has high transmittance for laser light with wavelength λ1 = 1064 nm + Δλ1. At this point, the diffraction efficiency for pump light with wavelength λ1 within the cavity is 99%. The third shaping lens 10 is a convex lens with a radius of curvature of 100 mm, coated on both sides with a broadband dielectric film that enhances the transmittance of Stokes light up to 1240 nm. The second bulk Bragg grating 11 is a bulk Bragg grating with a center wavelength of 1240 nm and a diffraction efficiency of 99%, coated on the surface with a broadband dielectric film that enhances the transmittance of Stokes light up to 1240 nm. The surface normal direction is perpendicular to the Stokes light... The included angle is θ2; the second heating patch element 13 is attached to the lower surface of the second body Bragg grating 11 with silicone grease, and the second body Bragg grating 11 is heated to temperature T2 by setting voltage V2 through the second DC power supply 15, so that the center wavelength of the second body Bragg grating 11 becomes λ2=1240nm+Δλ2 (Δλ2 is very small, so that the broadband dielectric film that is anti-reflective to 1240nm still has high transmittance to laser with wavelength λ2=1240nm+Δλ2). At this time, the diffraction efficiency of Stokes light with wavelength λ2 in the cavity is 92%.

[0077] The distance between the input mirror 3 and the left end face of the laser gain medium 4 is L1 = 20mm; the distance between the right end face of the gain medium 4 and the first shaping lens 5 is L2 = 20mm; the distance between the first shaping lens 5 and the left end face of the diamond crystal 6 is L3 = 20mm; the distance between the right end face of the diamond crystal 6 and the beam splitter 7 is L4 = 35mm; the distance between the beam splitter 7 and the second shaping lens 8 is L5, which is adjustable from 58mm to 62mm; the distance between the second shaping lens 8 and the surface of the first bulk Bragg grating 9 is L6 = 30mm; the distance between the beam splitter 7 and the third shaping lens 10 is L7, which is adjustable from 60mm to 64mm; and the distance between the third shaping lens 10 and the surface of the second bulk Bragg grating 11 is L8 = 30mm.

[0078] By adjusting the voltage V1 of the first DC power supply 14, the temperature T1 of the first heating patch element 12 is changed, thereby changing the temperature of the first bulk Bragg grating 9 to T1, and thus changing the center wavelength of the first bulk Bragg grating 9 to λ1. The first DC power supply voltage V1 is adjustable from 0 to 15V, so that the tuning range of the temperature T1 of the first heating patch element 12 is 10℃-90℃, and the tuning range of the center wavelength λ1 of the first bulk Bragg grating 9 is λ1. 1min -λ 1max Simultaneously, by adjusting the voltage V2 of the second DC power supply 15, the temperature T2 of the second heating patch element 13 is changed, thereby changing the temperature of the second volume Bragg grating 11 to T2, and thus changing the center wavelength of the second volume Bragg grating 11 to λ2. The second DC power supply voltage V2 is adjustable from 0-15V, making the temperature T2 of the second heating patch element 13 tuned within a range of 10℃-90℃, and making the center wavelength λ2 of the second volume Bragg grating 11 tuned within a range of λ2. 2min -λ 2max .

[0079] The 808nm pump light generated by pump source 1 is focused onto the laser gain medium 4, i.e., the center of the Nd:YVO4 crystal, after passing through focusing lens 2 and input mirror 3. The radius of the 808nm pump light spot is 185μm. When the 808nm pump light is focused onto the end face of the Nd:YVO4 crystal, its energy is absorbed and transferred to neodymium ions (Nd) in the crystal. 3+ Neodymium ions in Nd:YVO4 crystals are excited to a higher energy level after absorbing energy. When the neodymium ions return from the higher energy level to a lower energy level, they generate a wavelength of λ1 and a frequency of ω. p The laser radiation. The pump light with wavelength λ1 is focused at the center of the diamond crystal 6 after passing through the first shaping lens 5. The waist radius of the pump beam with wavelength λ1 is 73μm. After focusing, the efficiency of the pump light with wavelength λ1 is improved, and non-target wavelength light can be filtered more easily. The frequency is ω p The pump light excites the ground-state atoms of diamond crystal 6 to a virtual Raman upper level, simultaneously generating a frequency of ω. S Raman photons and a frequency of ω R The optical phonon, and satisfying ω p =ω S +ω R The Raman shift of diamond crystal 6 is 1332 cm⁻¹. -1When the pump light wavelength is λ1, the excited Stokes light wavelength is λ2. By adjusting the distance L5 between the beam splitter 7 and the second shaping lens 8, the straight cavity composed of the input mirror 3, the beam splitter 7, and the first volume Bragg grating 9 satisfies the parameter matching condition for the pump light with wavelength λ1. This causes the remaining unconverted pump light with wavelength λ1 to diffract at the first volume Bragg grating 9 after passing through the beam splitter 7 and the second shaping lens 8, resulting in the pump light with wavelength λ1 oscillating and amplifying in the straight cavity. The diffraction compresses the width of the pump light with wavelength λ1, making the width of the pump light with wavelength λ1 oscillating in the cavity narrower and increasing the energy density. Simultaneously, by adjusting the distance L7 between the beam splitter 7 and the third shaping lens 10, the input mirror 3, the beam splitter 7, and the V-shaped cavity satisfy the parameter matching condition for the Stokes light with wavelength λ2 generated by the stimulated Raman effect, causing the Stokes light with wavelength λ2 to oscillate and amplify in the V-shaped cavity. Stokes light with a wavelength of λ2 is diffracted at the second body Bragg grating 11. The diffraction compresses the linewidth of the Stokes light with a wavelength of λ2, thereby outputting a narrow-linewidth, high-power laser with a wavelength of λ2.

[0080] In summary, this invention proposes a narrow-linewidth internal cavity Raman laser with tunable output wavelength based on a combination of a V-cavity and a straight cavity. An 808nm laser from a high-power pump source is coupled into the resonant cavity. By adjusting the DC power supply voltage, the temperature of the heating patch element is changed, thereby altering the temperature of the bulk Bragg grating. This achieves tunable center wavelength of the bulk Bragg grating, enabling the 808nm laser to excite the Nd:YVO4 laser gain medium within the cavity to generate a laser with wavelength λ1 at λ... 1min -λ 1max A tunable pump light with wavelength λ1 is diffracted by a volume Bragg grating within a straight cavity, resulting in linewidth compression and oscillation amplification. Simultaneously, the tunable narrow-linewidth pump light with wavelength λ1 excites the diamond crystal to produce a wavelength λ2 within λ... 2min -λ 2max Tunable Stokes light is amplified by oscillation within a V-shaped cavity via a beam splitter, and then diffracted by a volume Bragg grating to compress the linewidth, achieving a wavelength range of λ. 2min -λ 2max Tunable, narrow-linewidth, high-power laser output.

[0081] Example 3

[0082] See Figure 3A wavelength-tunable linearly polarized narrow-linewidth intracavity Raman laser includes: a pump source 1, a focusing lens 2, an input mirror 3, a Brewster-cut crystal 16, a first shaping lens 5, a diamond crystal 6, a beam splitter 7, a second shaping lens 8, a first bulk Bragg grating 9, a first heating patch element 12, a third shaping lens 10, a second bulk Bragg grating 11, a second heating patch element 13, a first DC power supply 14, and a second DC power supply 15.

[0083] The first optical signal output from pump source 1 is focused by focusing lens 2 and then enters Brewster cut crystal 16 through input mirror 3. Brewster cut crystal 16 filters out pump light with polarization direction perpendicular to the incident plane and retains pump light with polarization direction parallel to the incident plane. After gaining, a second optical signal is generated. The second optical signal is shaped by the first shaping lens 5 and then enters diamond crystal 6 to generate stimulated Raman effect and generate Stokes light.

[0084] The left end face of the Brewster-cut crystal 16 is straight, and the right end face is inclined. The upper and lower end faces are parallel, and the front and rear end faces are parallel. The angle of the right inclined face is set according to the filtering of light rays with specific polarization directions. This design makes the output light rays form an angle with the incident light rays. The composite resonant cavity includes a pump light oscillation cavity and a seed light oscillation cavity. The pump light oscillation cavity is composed of a pump light beam splitter cavity with a common optical axis and an SRS effect cavity. In this embodiment, the SRS effect cavity has a bend in the Brewster-cut crystal 16. Therefore, the shape of the pump light oscillation cavity in this embodiment is slightly different from the straight cavity in embodiments 1 and 2, but the principle remains the same. The V-shaped cavity is composed of a Stokes beam splitter cavity with an angled optical axis and an SRS effect cavity. Similarly, the seed light oscillation cavity in this embodiment is slightly different from the V-shaped cavity in embodiments 1 and 2, but the principle remains the same.

[0085] Pump source 1 outputs pump light with a wavelength of 808nm and a spectral linewidth of <1nm; focusing lens 2 is a convex lens with a radius of curvature of 50mm, coated on both sides with a broadband dielectric film that enhances the transmittance of the pump light wavelength of 808nm; input mirror 3 is a plano-concave mirror with a radius of curvature of 75mm, coated on both sides with a broadband dielectric film that enhances the transmittance of the pump light wavelength of 808nm, and the concave side is coated with a broadband dielectric film with a reflectance of >99.8% for 1064nm and Stokes light of 1240nm; Brewster-cut crystal 16 is a Brewster-cut Nd:YVO4 crystal, coated on both sides with a broadband dielectric film that enhances the transmittance of the pump light wavelengths of 808nm, 1064nm, and 1240nm; first shaping lens 5 is a convex lens with a radius of curvature of 100mm, coated on both sides with a broadband dielectric film that enhances the transmittance of the pump light wavelengths of 1064nm and 1240nm; diamond crystal 6 is a... <110> Axially cut synthetic diamond crystal, measuring 7×4×1.2mm. 3The first beam splitter 7 is a plane mirror, coated on both sides with a broadband dielectric film that enhances the transmission of pump light at 1064nm and Stokes light at 1240nm, and a broadband dielectric film with a reflectivity >99.8% for Stokes light at 1240nm. The angle θ1 between the normal direction of the beam splitter 7 surface and the incident pump light is 10°. The second shaping lens 8 is a convex lens with a radius of curvature of 100mm, coated on both sides with a broadband dielectric film that enhances the transmission of pump light at 1064nm. The first bulk... The bulk Bragg grating 9 is a bulk Bragg grating with a center wavelength of 1064nm and a diffraction efficiency of 99%. Its surface is coated with a broadband dielectric film that enhances the light transmission at 1064nm, and the surface normal is parallel to the pump light direction. A first heating element 12 is attached to the lower surface of the first bulk Bragg grating 9 using silicone grease. A first DC power supply 14 sets a voltage V1 to heat the first bulk Bragg grating 9 to a temperature T1, causing the center wavelength of the first bulk Bragg grating 9 to become λ1 = 1064nm + Δλ1 (Δλ1 is very small, ensuring sufficient diffraction efficiency at 1064nm). The broadband dielectric film, which is transparent, still has high transmittance for laser light with wavelength λ1 = 1064 nm + Δλ1. At this point, the diffraction efficiency for pump light with wavelength λ1 within the cavity is 99%. The third shaping lens 10 is a convex lens with a radius of curvature of 100 mm, coated on both sides with a broadband dielectric film that enhances the transmittance of Stokes light up to 1240 nm. The second bulk Bragg grating 11 is a bulk Bragg grating with a center wavelength of 1240 nm and a diffraction efficiency of 99%, coated on the surface with a broadband dielectric film that enhances the transmittance of Stokes light up to 1240 nm. The surface normal direction is perpendicular to the Stokes light... The included angle is θ2; the second heating patch element 13 is attached to the lower surface of the second body Bragg grating 11 with silicone grease, and the second body Bragg grating 11 is heated to temperature T2 by setting voltage V2 through the second DC power supply 15, so that the center wavelength of the second body Bragg grating 11 becomes λ2=1240nm+Δλ2 (Δλ2 is very small, so that the broadband dielectric film that is anti-reflective to 1240nm still has high transmittance to laser with wavelength λ2=1240nm+Δλ2). At this time, the diffraction efficiency of Stokes light with wavelength λ2 in the cavity is 92%.

[0086] The distance L9 between the input mirror 3 and the intersection of the left end face of the Brewster-cut crystal 16 with the optical axis is 20mm; the distance L10 between the intersection of the right end face of the Brewster-cut crystal 16 with the optical axis and the first shaping lens 5 is 20mm; the distance L3 between the first shaping lens 5 and the left end face of the diamond crystal 6 is 20mm; the distance L4 between the right end face of the diamond crystal 6 and the beam splitter 7 is 35mm; the distance L5 between the beam splitter 7 and the second shaping lens 8 is adjustable from 58mm to 62mm; the distance L6 between the second shaping lens 8 and the surface of the first bulk Bragg grating 9 is 30mm; the distance L7 between the beam splitter 7 and the third shaping lens 10 is adjustable from 60mm to 64mm; and the distance L8 between the third shaping lens 10 and the surface of the second bulk Bragg grating 11 is 30mm.

[0087] By adjusting the voltage V1 of the first DC power supply 14, the temperature T1 of the first heating patch element 12 is changed, thereby changing the temperature of the first bulk Bragg grating 9 to T1, and thus changing the center wavelength of the first bulk Bragg grating 9 to λ1. The first DC power supply voltage V1 is adjustable from 0 to 15V, so that the tuning range of the temperature T1 of the first heating patch element 12 is 10℃-90℃, and the tuning range of the center wavelength λ1 of the first bulk Bragg grating 9 is λ1. 1min -λ 1max Simultaneously, by adjusting the voltage V2 of the second DC power supply 15, the temperature T2 of the second heating patch element 13 is changed, thereby changing the temperature of the second volume Bragg grating 11 to T2, and thus changing the center wavelength of the second volume Bragg grating 11 to λ2. The second DC power supply voltage V2 is adjustable from 0-15V, making the temperature T2 of the second heating patch element 13 tuned within a range of 10℃-90℃, and making the center wavelength λ2 of the second volume Bragg grating 11 tuned within a range of λ2. 2min -λ 2max .

[0088] The 808nm pump light generated by pump source 1 is focused onto the Brewster-cut crystal 16, i.e., the center of the Brewster-cut Nd:YVO4 crystal, after passing through focusing lens 2 and input mirror 3. The radius of the 808nm pump light spot is 185μm. When the 808nm pump light is focused onto the end face of the Nd:YVO4 crystal, its energy is absorbed and transferred to neodymium ions (Nd) in the crystal. 3+ Neodymium ions in Nd:YVO4 crystals are excited to a higher energy level after absorbing energy. When the neodymium ions return from the higher energy level to a lower energy level, they generate a wavelength of λ1 and a frequency of ω. p The laser radiation. The pump light with wavelength λ1 oscillates in the pump light oscillation cavity. Whenever the pump light with wavelength λ1 reaches the right surface of the Brewster-cut crystal 16, the pump light with wavelength λ1 polarized perpendicular to the incident plane is reflected and lost, while the pump light with wavelength λ1 polarized parallel to the incident plane is transmitted through the Brewster-cut Nd:YVO4 crystal. Therefore, the polarization direction of the pump light with wavelength λ1 oscillating in the pump light oscillation cavity is parallel to the incident plane. This pump light with wavelength λ1 polarized parallel to the incident plane is focused on the center of the diamond crystal 6 after passing through the first shaping lens 5. The waist radius of this pump beam with wavelength λ1 is 73μm. After focusing, the efficiency of the pump light with wavelength λ1 is improved, and non-target wavelength light can be filtered more easily. By adjusting the axial direction of the diamond crystal, the diamond crystal... <111> The axial direction is parallel to the polarization direction of the pump light with wavelength λ1 to maximize the stimulated Raman effect. The frequency is ω. p The pump light excites the ground-state atoms of diamond crystal 6 to a virtual Raman upper level, simultaneously generating a frequency of ω.S Raman photons and a frequency of ω R The optical phonon, and satisfying ω p =ω S +ω R The Raman shift of diamond crystal 6 is 1332 cm⁻¹. -1 When the pump light wavelength is λ1, the excited Stokes light wavelength is λ2, and its polarization direction is the same as that of the pump light with wavelength λ1, both parallel to the incident plane. By adjusting the distance L5 between the beam splitter 7 and the second shaping lens 8, the pump light oscillation cavity satisfies the parameter matching condition for the pump light with wavelength λ1. This causes the remaining unconverted pump light with wavelength λ1 to diffract at the first volume Bragg grating 9 after passing through the beam splitter 7 and the second shaping lens 8, resulting in the pump light with wavelength λ1 oscillating and amplifying within the pump light oscillation cavity. The diffraction compresses the bandwidth of the pump light with wavelength λ1, narrowing the bandwidth of the pump light with wavelength λ1 oscillating within the cavity and increasing its energy density. Simultaneously, by adjusting the distance L7 between the beam splitter 7 and the third shaping lens 10, the seed light oscillation cavity satisfies the parameter matching condition for the Stokes light with wavelength λ2 generated by the stimulated Raman effect, causing the Stokes light with wavelength λ2 to oscillate and amplify within the seed light oscillation cavity. Stokes light with a wavelength of λ2 is diffracted at the second body Bragg grating 11. The diffraction compresses the linewidth of the Stokes light with a wavelength of λ2, thereby outputting a narrow-linewidth, high-power laser with a wavelength of λ2 and a polarization direction parallel to the incident plane.

[0089] In summary, this invention proposes a linearly polarized narrow-linewidth intracavity Raman laser with tunable output wavelength based on a composite structure. An 808nm laser from a high-power pump source is coupled into the resonant cavity. By adjusting the DC power supply voltage, the temperature of the heating patch element is changed, thereby altering the temperature of the bulk Bragg grating. This achieves tunable center wavelength of the bulk Bragg grating, enabling the 808nm laser to excite a Brewster-cut Nd:YVO4 crystal within the cavity to generate a Raman laser with wavelength λ1 at λ... 1min -λ 1max A tunable pump light with a polarization parallel to the incident plane, exhibiting linear polarization of wavelength λ1, is diffracted by a volume Bragg grating within the cavity, resulting in linewidth compression and oscillation amplification. Simultaneously, a tunable linear polarization pump light with a narrow linewidth of λ1 excites the diamond crystal to produce a pump light with wavelength λ2 within λ... 2min -λ 2max Tunable Stokes light with a polarization direction parallel to the incident plane is oscillated and amplified in a seed light oscillation cavity by a beam splitter, and then diffracted by a volume Bragg grating to achieve linewidth compression, thus realizing a wavelength in the range of λ. 2min -λ 2max Tunable linearly polarized, narrow-linewidth, high-power laser output.

[0090] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A narrow-linewidth internal cavity Raman laser, characterized in that, It includes a laser emitting section, an SRS effect cavity, a beam splitter, a pump beam splitter, and a Stokes beam splitter; the pump beam splitter and the SRS effect cavity are coaxial and together constitute a pump beam oscillation cavity, and the Stokes beam splitter and the SRS effect cavity are at an angle to each other and together constitute a seed beam oscillation cavity. The laser emitting unit is used to emit a first optical signal with a tunable first preset power and a first preset wavelength into the SRS effect cavity, and the first optical signal is amplified in the SRS effect cavity to generate a second optical signal. The first optical signal and the second optical signal are pump lights with different powers and wavelengths. In the SRS effect cavity, the second optical signal is converted into Stokes light using the stimulated Raman effect, and a portion of unconverted pump light remains. The Stokes light and the unconverted pump light are separated by a beam splitter, so that the Stokes light oscillates in the seed light oscillation cavity, and the pump light remaining from the stimulated Raman effect oscillates in the pump light oscillation cavity. The Stokes beam enters the Stokes beam splitter cavity and is diffracted by a second body Bragg grating set inside the cavity. The diffraction compresses the linewidth of the Stokes beam, thereby outputting a narrow linewidth laser. The pump light that is not converted by the stimulated Raman effect enters the pump light beam splitter cavity and oscillates in the pump light oscillation cavity. The unconverted pump light is filtered and diffracted by the first volume Bragg grating set in the cavity, and the narrow-linewidth residual pump light obtained by diffraction is reflected back into the SRS effect cavity to realize the amplification of the narrow-linewidth second signal light. The narrow-linewidth second optical signal again utilizes the stimulated Raman effect to generate narrow-linewidth Stokes light, and further compresses the linewidth through diffraction by the second volume Bragg grating.

2. The narrow linewidth internal cavity Raman laser according to claim 1, characterized in that, The laser emitting unit includes a pump source (1) and a focusing lens (2). The pump source (1) emits a first optical signal with a tunable first preset power and a first preset wavelength, which is then focused and output by the focusing lens (2).

3. The narrow linewidth internal cavity Raman laser according to claim 2, characterized in that, The beam splitting section is implemented using a beam splitter (7).

4. A narrow linewidth internal cavity Raman laser according to claim 3, characterized in that, An input mirror (3), a laser gain medium (4), a first shaping lens (5), and a diamond crystal (6) are set in the SRS effect cavity. The first optical signal output by the pump source (1) is focused by the focusing lens (2) and then enters the laser gain medium (4) through the input mirror (3), and a second optical signal is generated after amplification. The second optical signal is shaped by the first shaping lens (5) and then enters the diamond crystal (6) to generate stimulated Raman effect and generate Stokes light.

5. A narrow-linewidth internal cavity Raman laser according to claim 3, characterized in that, An input mirror (3), a Brewster cut crystal (16), a first shaping lens (5), and a diamond crystal (6) are set in the SRS effect cavity. The first optical signal output by the pump source (1) is focused by the focusing lens (2) and then enters the Brewster cut crystal (16) through the input mirror (3). The Brewster cut crystal (16) filters out the pump light whose polarization direction is perpendicular to the incident plane and retains the pump light whose polarization direction is parallel to the incident plane. After gaining, a second optical signal is generated. The second optical signal is shaped by the first shaping lens (5) and then enters the diamond crystal (6) to generate stimulated Raman effect and generate Stokes light.

6. A narrow linewidth internal cavity Raman laser according to claim 4 or 5, characterized in that, A second shaping lens (8) and a first volume Bragg grating (9) are provided in the pump beam splitter cavity, and a third shaping lens (10) and a second volume Bragg grating (11) are provided in the Stokes beam splitter cavity; The residual unconverted pump light is transmitted through the beam splitter (7), then enters the second shaping lens (8) for shaping, and then enters the first volume Bragg grating (9) for diffraction. The narrow-linewidth residual pump light obtained by diffraction is reflected back to the gain component in the SRS effect cavity to realize the amplification of the narrow-linewidth second optical signal. After being reflected by the beam splitter (7), the Stokes light enters the third shaping lens (10) for shaping, and then enters the second volume Bragg grating (11) for diffraction, outputting a stable narrow linewidth laser.

7. A narrow-linewidth internal cavity Raman laser according to claim 6, characterized in that, It also includes a first heating patch element (12), a second heating patch element (13), a first DC power supply (14), and a second DC power supply (15). The first heating patch element (12) is attached to the lower surface of the first bulk Bragg grating (9) with silicone grease. The first DC power supply (14) is used to set a specific voltage to heat the first bulk Bragg grating (9) to a specific temperature, thereby changing the center wavelength of the first bulk Bragg grating (9) to achieve the diffraction screening effect on the residual unconverted pump light. The second heating patch element (13) is attached to the lower surface of the second volume Bragg grating (11) with silicone grease. A specific voltage is set by the second DC power supply (15) to heat the second volume Bragg grating (11) to a specific temperature, thereby changing the center wavelength of the second volume Bragg grating (11) to achieve the diffraction and sieving effect of the Stokes light.

8. A narrow linewidth internal cavity Raman laser according to claim 4, characterized in that, The laser gain medium (4) is an Nd:YAG crystal, and the diamond crystal (6) is a linear laser. <110> The artificial diamond crystal is cut from the axial direction, and the beam splitter (7) is a plane mirror.

9. A narrow linewidth internal cavity Raman laser according to claim 5, characterized in that, Diamond crystal (6) is along <110> The artificial diamond crystal is axially cut. The beam splitter (7) is a plane mirror. The Brewster-cut crystal (16) is a Brewster-cut Nd:YVO4 crystal. The left end face of the Brewster-cut crystal (16) is a straight surface, and the right end face of the Brewster-cut crystal (16) is a beveled surface.

10. A narrow-linewidth internal cavity Raman laser according to claim 8 or 9, characterized in that, The angle between the surface normal of the beam splitter (7) and the optical axis of the SRS effect cavity is 10°.

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