Narrow-linewidth tunable Raman laser and emission method

Abstract

The invention discloses a narrow-linewidth tunable Raman laser and an emission method, and relates to the field of Raman lasers, the narrow-linewidth tunable Raman laser comprises a half-wave plate, a pumping source and a focusing lens, the pumping source and the focusing lens are respectively arranged on two sides of the half-wave plate, and a laser resonant cavity is arranged on the other side of the focusing lens. A laser resonant cavity is arranged on one side of the laser cavity, a lock cavity frequency multiplier is arranged on the other side of the laser resonant cavity, a shaping lens group is arranged between the laser resonant cavity and the lock cavity frequency multiplier, a dichroic mirror is arranged on the other side of the lock cavity frequency multiplier, and the laser resonant cavity is of a V-shaped cavity structure formed by an input mirror, an output mirror and a reflective blazed grating. A diamond crystal is arranged between the input mirror and the output mirror, the reflection type blazed grating is arranged below the diamond crystal, the stability of the laser resonant cavity is improved through the design of the reflector in the cavity, wavelength adjustment accurate to 0.01 nm is achieved, and loss in the transmission process is reduced through the cavity locking frequency multiplier of an annular cavity structure.

Description

[0001] Methodology Area

[0002] The invention relates to the field of Raman lasers, and in particular to a narrow linewidth tunable Raman laser and an emission method.

[0003] Background Methods

[0004] Visible light lasers with narrow linewidth and tunable wavelength have broad application prospects in the fields of laser radar, metrology and quantum physics. At present, the methods for obtaining tunable visible light bands include optical parametric oscillation (OPO) and rare earth ion radiation. However, the output of OPO scheme is often accompanied by line width broadening and beam deterioration. The wavelength output of rare earth ion radiation is limited by the fluorescence spectrum of rare earth ions themselves, and it is difficult to achieve a larger range of wavelength expansion. With the development of nonlinear technology, the stimulated Raman scattering (SRS) effect caused by the molecular vibration of Raman media has become an important means to achieve large laser frequency conversion. In this section, SRS-based Raman lasers have many advantages: Raman frequency shift can be used to achieve laser output of wavelengths with vacant emission cross sections of rare earth ions. Currently, people have used Raman conversion to achieve output from deep ultraviolet to mid-wave infrared; Raman frequency shift is only related to the medium lattice vibration and has nothing to do with the frequency of the pump light. Therefore, tuning the pump light frequency can obtain Raman light with the same frequency tuning range; Raman gain is proportional to the pump light intensity, there is no saturation effect or spatial hole burning effect, and the Raman laser output power directly depends on the pump light power, which can achieve energy conversion close to the quantum efficiency limit and output with narrow linewidth.

[0005] At present, researchers have achieved Raman laser output through straight cavity and ring cavity. However, when operating at high power, the Raman medium in the resonant cavity absorbs the residual pump light and produces a thermal effect, which greatly interferes with the stability of the resonant cavity. At the same time, the Stokes return light cannot be separated from the pump light, causing it to return directly to the position of the pump light source, which is easy to damage it and affect its stability. Therefore, it greatly limits the power improvement and application of Raman lasers. In addition, there is currently an important demand for visible light Raman lasers with adjustable narrow linewidth wavelength range for space environment detection, but it is difficult to achieve narrow linewidth and visible light wavelength adjustment at the same time based on nonlinear frequency conversion of traditional solid-state lasers.

[0006] Therefore, a narrow linewidth tunable Raman laser and an emission method are provided to solve the above problems. Summary of the invention

[0007] The purpose of the present invention is to provide a narrow linewidth tunable Raman laser and an emission method, reduce the demand for optical isolators, improve the stability of the laser resonant cavity, reduce the loss during transmission, achieve precise adjustment of the wavelength of the optical signal, reduce the linewidth of the output optical signal, and ultimately achieve narrow linewidth tunable wavelength output.

[0008] To achieve the above-mentioned purpose, the present invention provides a narrow linewidth tunable Raman laser and an emission method, comprising a half wave plate and a pump source and a focusing lens respectively arranged on both sides of the half wave plate, a laser resonant cavity is arranged on the other side of the focusing lens, a cavity-locked frequency doubler is arranged on the other side of the laser resonant cavity, a shaping lens group is arranged between the laser resonant cavity and the cavity-locked frequency doubler, a binocular mirror is arranged on the other side of the cavity-locked frequency doubler, the laser resonant cavity is arranged as a V-shaped cavity structure composed of an input mirror, an output mirror and a reflective blazed grating, a diamond crystal is arranged between the input mirror and the output mirror, and the reflective blazed grating is arranged below the diamond crystal.

[0009] Preferably, the locked cavity frequency multiplier includes a frequency doubling crystal and a second locked cavity reflector and a locked cavity output mirror symmetrically arranged on both sides of the frequency doubling crystal, a locked cavity input mirror is arranged above the second locked cavity reflector, and a first locked cavity reflector is arranged above the locked cavity output mirror, and the locked cavity input mirror and the first locked cavity reflector are symmetrically arranged according to the frequency doubling crystal.

[0010] Preferably, the shaping lens group includes two convex lenses, and the surfaces of the two convex lenses are coated with a broadband dielectric film with high transmittance to Stokes light, and the wavelength range of the Stokes light is set to 1.18-1.26 μm.

[0011] Preferably, the surface of the focusing lens is coated with a broadband dielectric film that enhances the transmittance of the pump light, and the wavelength range of the pump light is set to 1.02-1.08 μm. The surface of the binocular mirror is coated with a broadband dielectric film that has high reflection for Stokes light and high transmission for frequency-doubled light, and the wavelength range of the Stokes light is set to 1.18-1.26 μm, and the wavelength range of the frequency-doubled light is set to 0.59-0.63 μm.

[0012] Preferably, the reflectivity of the input mirror and the reflectivity of the output mirror are different from the reflectivity of the reflective blazed grating. The input mirror adopts a plano-concave reflector with a curvature radius of 50 mm. The plane of the input mirror is coated with a broadband dielectric film for enhancing the transmittance of the pump light. The concave surface of the input mirror is coated with a broadband dielectric film with a reflectivity of Stokes light greater than 99.9%. The wavelength range of the Stokes light is set to 1.18-1.26 μm. The output mirror adopts a plano-concave reflector with a curvature radius of 100 mm. The output mirror is a concave surface of the output mirror coated with a broadband dielectric film having a reflectivity greater than 99.9% for pump light and a transmittance of 0.1%-0.5% for Stokes light, the flat surface of the output mirror is coated with a broadband dielectric film that is transmissive to Stokes light, the wavelength range of Stokes light is set to 1.18-1.26μm, the reflectivity of the reflective blazed grating is greater than 99.9%, the reflection band is set to 1.18-1.26μm, and a plurality of grating lines are arranged on the reflective blazed grating.

[0013] Preferably, the diamond crystal is an artificial diamond crystal cut along an axis facing a diagonal line, and the size of the diamond crystal is 7×4×1.2 mm. 3 The left and right sides of the diamond crystal are coated with broadband dielectric films with a transmittance of more than 99.5% for pump light and Stokes light. The wavelength range of the pump light is set to 1.02-1.08 μm, and the wavelength range of the Stokes light is set to 1.18-1.26 μm.

[0014] Preferably, the cavity lock input mirror adopts a plane reflector, the left side of the cavity lock input mirror is coated with a broadband dielectric film for enhancing the transmittance of Stokes light, and the wavelength range of Stokes light is set to 1.18-1.26μm, the right side of the cavity lock input mirror is coated with a broadband dielectric film with a transmittance of 2-4% to Stokes light, and the wavelength range of Stokes light is set to 1.18-1.26μm, and the cavity lock output mirror adopts a plano-concave reflector with a curvature radius of 100mm, and the concave surface of the cavity lock output mirror is coated with a broadband dielectric film with a reflectance of greater than 99.9% to Stokes light and a broadband dielectric film with a transmittance of greater than 90% to doubled frequency light, and the wavelength range of Stokes light is set to 1.18-1.26μm, and the wavelength range of doubled frequency light is set to 1.18-1.26μm. The long range is set to 0.59-0.63μm, the plane of the cavity lock output mirror is coated with a broadband dielectric film with a transmittance of more than 99.5% for the doubled frequency light, and the wavelength range of the doubled frequency light is set to 0.59-0.63μm, the first cavity lock reflector adopts a plane reflector, and the surface of the first cavity lock reflector is coated with a broadband dielectric film with a reflectance of more than 99.9% for the Stokes light, and the wavelength range of the Stokes light is set to 1.18-1.26μm, the second cavity lock reflector adopts a plano-concave reflector with a curvature radius of 100mm, and the concave surface of the second cavity lock reflector is coated with a broadband dielectric film with a reflectance of more than 99.9% for the Stokes light, and the wavelength range of the Stokes light is set to 1.18-1.26μm.

[0015] Preferably, the frequency doubling crystal is an LBO crystal, the cutting angle of the LBO crystal is 90°, the temperature phase of the LBO crystal is 0°, and the size of the LBO crystal is designed to be 4×4×10 mm. 3 The left and right sides of the LBO crystal are coated with broadband dielectric films for enhancing the transmittance of Stokes light and frequency-doubled light. The wavelength range of Stokes light is set to 1.18-1.26 μm, and the wavelength range of frequency-doubled light is set to 0.59-0.63 μm.

[0016] Preferably, the emission method of the narrow linewidth tunable Raman laser comprises the following steps:

[0017] S1: The pump source emits pump light, which is coupled through a half-wave plate and a focusing lens;

[0018] S2: The coupled pump light passes through the input mirror and enters the diamond crystal. The diamond crystal converts the pump light into a Stokes light signal using the SRS effect. The angle of the reflective blazed grating is adjusted to precisely adjust the wavelength. The precision adjustment range is set to [0.01-0.1] nm.

[0019] S3: The Stokes optical signal passes through the output mirror and enters the shaping lens group, and the shaping lens group couples the Stokes optical signal;

[0020] S4: The cavity-locked frequency doubler frequency-doubles the coupled Stokes optical signal and outputs frequency-doubled light;

[0021] S5: The binocular mirror separates the frequency-doubled light from the leaked Stokes light signal and outputs a narrow-linewidth visible light laser.

[0022] Preferably, in step S1, both the first preset power and the first preset wavelength of the pump light are tunable.

[0023] Therefore, the present invention adopts a narrow linewidth tunable Raman laser and emission method of the above structure, which has the following beneficial effects:

[0024] (1) Through the design of the intracavity reflector, the residual pump light and the Stokes light are separated at the reflector, which reduces the coating requirements of the binocular mirror and the optical isolator, thereby improving the stability of the laser resonant cavity;

[0025] (2) Using a reflective blazed grating as one of the cavity mirrors of the laser resonant cavity, the wavelength adjustment can be achieved with an accuracy of 0.01 nm, making it applicable in fields that require accurate spectral lines at relevant atomic energy levels;

[0026] (3) A cavity-locked frequency doubler with a ring cavity structure is used to reduce the loss during transmission and effectively increase the length of the cavity-locked frequency doubler, thereby reducing the line width of the output optical signal and achieving a narrow line width of 0.59-0.63μm tunable wavelength output.

[0027] The method scheme of the present invention is further described in detail below through the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a structural diagram of a narrow linewidth tunable Raman laser of the present invention;

[0029] Figure 2 This is a structural diagram of a cavity-locked frequency multiplier for a narrow linewidth tunable Raman laser according to the present invention;

[0030] Figure 3 This is a structural diagram of a reflective blazed grating of a narrow linewidth tunable Raman laser of the present invention.

[0031] Among them: 1. Pump source; 2. Half wave plate; 3. Focusing lens; 4. Input mirror; 5. Diamond crystal; 6. Reflective blazed grating; 7. Output mirror; 8. Shaping lens group; 9. Locked cavity frequency doubler; 91. Locked cavity input mirror; 92. First locked cavity reflector; 93. Second locked cavity reflector; 94. Frequency doubling crystal; 95. Locked cavity output mirror; 10. Dichroic mirror. DETAILED DESCRIPTION

[0032] The method scheme of the present invention is further described below through drawings and embodiments.

[0033] Unless otherwise defined, method terms or scientific terms used in the present invention shall have the common meanings understood by one of ordinary skill in the art to which the present invention belongs.

[0034] The words "include" or "comprises" and the like used in the present invention mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of also including other elements. The orientation or position relationship indicated by the terms "inside", "outside", "upper", "lower", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention. When the absolute position of the described object changes, the relative position relationship may also change accordingly. In the present invention, unless otherwise clearly specified and limited, the terms "attachment" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] Example

[0036] like Figure 1 As shown, the present invention provides a narrow linewidth tunable Raman laser and an emission method, comprising a half wave plate 2 and a pump source 1 and a focusing lens 3 respectively arranged on both sides of the half wave plate 2, the pump source 1 is used to output a frequency of ω P The linearly polarized pump light has a spectral line width of less than 0.1 nm. The half wave plate 2 is used to adjust the polarization state of the pump light. The focusing lens 3 is used to focus the pump light signal into the crystal of the Raman laser. The surface of the focusing lens 3 is coated with a broadband dielectric film that increases the transmittance of the pump light. The wavelength range of the pump light is set to 1.02-1.08 μm.

[0037] A laser resonant cavity is arranged on the other side of the focusing lens 3, a cavity-locked frequency doubler 9 is arranged on the other side of the laser resonant cavity, a shaping lens group 8 is arranged between the laser resonant cavity and the cavity-locked frequency doubler 9, and a binocular mirror 10 is arranged on the other side of the cavity-locked frequency doubler 9;

[0038] The shaping lens group 8 includes two convex lenses, and the surfaces of the two convex lenses are coated with a broadband dielectric film with high transmittance to Stokes light, and the wavelength range of the Stokes light is set to 1.18-1.26 μm;

[0039] The surface of the binochroic mirror 10 is coated with a broadband dielectric film that has high reflection for Stokes light and high transmission for doubled frequency light. The wavelength range of the Stokes light is set to 1.18-1.26 μm, and the wavelength range of the doubled frequency light is set to 0.59-0.63 μm.

[0040] The laser resonant cavity is set as a V-shaped cavity structure composed of an input mirror 4, an output mirror 7 and a reflective blazed grating 6. A diamond crystal 5 is arranged between the input mirror 4 and the output mirror 7, and the reflective blazed grating 6 is arranged below the diamond crystal 5.

[0041] The distance L1 between the input mirror 4 and the left side of the diamond crystal 5 is set to 25 mm, the distance L2 between the right side of the diamond crystal 5 and the output mirror 7 is set to 98 mm, and the distance L3 between the input mirror 4 and the reflective blazed grating 6 is set to 150 mm, wherein the distance L3 between the input mirror 4 and the reflective blazed grating 6 is adjustable, and the adjustment range is set to 40-400 mm;

[0042] The reflectivity of the input mirror 4 and the reflectivity of the output mirror 7 are all different from the reflectivity of the reflective blazed grating 6. The input mirror 4 adopts a plano-concave reflector with a curvature radius of 50 mm. The flat surface of the input mirror 4 is coated with a broadband dielectric film for enhancing the transmittance of the pump light. The concave surface of the input mirror 4 is coated with a broadband dielectric film for enhancing the transmittance of the pump light. The concave surface of the input mirror 4 is coated with a broadband dielectric film with a reflectivity of greater than 99.9% for Stokes light. The wavelength range of the Stokes light is set to 1.18-1.26 μm.

[0043] The output mirror 7 adopts a plano-concave reflector with a curvature radius of 100 mm. The concave surface of the output mirror 7 is coated with a broadband dielectric film with a reflectivity greater than 99.9% for pump light and a transmittance of 0.1%-0.5% for Stokes light. The flat surface of the output mirror 7 is coated with a broadband dielectric film with a transmittance in the 1.18-1.26 μm band, which is used to realize double-pass utilization of the pump light.

[0044] The diamond crystal 5 is a synthetic diamond crystal cut along an axis facing a diagonal line, and the size of the diamond crystal 5 is 7×4×1.2 mm. 3The left and right sides of the diamond crystal 5 are coated with broadband dielectric films with a transmittance of more than 99.5% for pump light and Stokes light. The wavelength range of the pump light is set to 1.02-1.08 μm, and the wavelength range of the Stokes light is set to 1.18-1.26 μm.

[0045] like Figure 2 As shown, the cavity lock frequency multiplier 9 includes a frequency doubling crystal 94 and a second cavity lock reflector 93 and a cavity lock output mirror 95 symmetrically arranged on both sides of the frequency doubling crystal 94, a cavity lock input mirror 91 is arranged above the second cavity lock reflector 93, and a first cavity lock reflector 92 is arranged above the cavity lock output mirror 95, and the cavity lock input mirror 91 and the first cavity lock reflector 92 are symmetrically arranged according to the frequency doubling crystal 94;

[0046] The distance L4 between the lock cavity input mirror 91 and the first lock cavity reflector 92 is set to 150 mm, the distance L5 between the lock cavity input mirror 91 and the lock cavity output mirror 95 is set to 100 mm, the distance L6 between the first lock cavity reflector 92 and the second lock cavity reflector 93 is set to 100 mm, the distance L7 between the second lock cavity reflector 93 and the left side of the frequency doubling crystal 94 is set to 51.5 mm, and the distance L8 between the right side of the frequency doubling crystal 94 and the lock cavity output mirror 95 is set to 51.5 mm;

[0047] The cavity lock input mirror 91 adopts a plane reflector, and the left side of the cavity lock input mirror 91 is coated with a broadband dielectric film for enhancing the transmittance of Stokes light, and the wavelength range of Stokes light is set to 1.18-1.26μm. The right side of the cavity lock input mirror 91 is coated with a broadband dielectric film with a transmittance of 2-4% to Stokes light, and the wavelength range of Stokes light is set to 1.18-1.26μm. The cavity lock output mirror 95 adopts a plano-concave reflector with a curvature radius of 100mm, and the concave surface of the cavity lock output mirror 95 is coated with a broadband dielectric film with a reflectance of more than 99.9% to Stokes light and a broadband dielectric film with a transmittance of more than 90% to doubled frequency light. The wavelength range of Stokes light is set to 1.18-1.26μm, and the wavelength range of doubled frequency light is set to 1.18-1.26μm. The range is set to 0.59-0.63μm, the plane of the locking cavity output mirror 95 is coated with a broadband dielectric film with a transmittance of more than 99.5% for the doubled frequency light, and the wavelength range of the doubled frequency light is set to 0.59-0.63μm, the first locking cavity reflector 92 adopts a plane reflector, and the surface of the first locking cavity reflector 92 is coated with a broadband dielectric film with a reflectance of more than 99.9% for the Stokes light, and the wavelength range of the Stokes light is set to 1.18-1.26μm, the second locking cavity reflector 93 adopts a plano-concave reflector with a curvature radius of 100mm, and the concave surface of the second locking cavity reflector 93 is coated with a broadband dielectric film with a reflectance of more than 99.9% for the Stokes light, and the wavelength range of the Stokes light is set to 1.18-1.26μm.

[0048] The frequency doubling crystal 94 uses LBO crystal. The cutting angle of LBO crystal is 90°, the temperature phase of LBO crystal is 0°, and the size of LBO crystal is designed to be 4×4×10mm 3 The left and right sides of the LBO crystal are coated with broadband dielectric films that enhance the transmittance of Stokes light and frequency-doubled light. The wavelength range of Stokes light is set to 1.18-1.26μm, and the wavelength range of frequency-doubled light is set to 0.59-0.63μm.

[0049] like Figure 3 As shown, the reflectivity and diffraction efficiency of the reflective blazed grating 6 are greater than 99.9%, the reflection band is set to 1.18-1.26 μm, a plurality of grating lines are set on the reflective blazed grating 6, the angle between the line normal a of the reflective blazed grating 6 and the grating normal b of the reflective blazed grating 6 is equal to the blaze angle γ of the reflective blazed grating 6, and the angle between the incident light and the grating normal b of the reflective blazed grating 6 is the light incident angle θ i , by rotating the displacement platform to change the incident angle of light θ i , the wavelength variation output can be realized, the grating constant d of the reflective blazed grating 6 is the distance between two adjacent grating lines, and in this embodiment, the grating constant d of the reflective blazed grating 6 is set to 2000nm;

[0050] The emission method of the narrow linewidth tunable Raman laser comprises the following steps:

[0051] S1: The pump source emits pump light, which is coupled through a half-wave plate and a focusing lens;

[0052] S2: The coupled pump light passes through the input mirror and enters the diamond crystal. The diamond crystal converts the pump light into a Stokes light signal using the SRS effect. The angle of the reflective blazed grating is adjusted to precisely adjust the wavelength. The precision adjustment range is set to [0.01-0.1] nm.

[0053] S3: The Stokes optical signal passes through the output mirror and enters the shaping lens group, and the shaping lens group couples the Stokes optical signal;

[0054] S4: The cavity-locked frequency doubler frequency-doubles the coupled Stokes optical signal and outputs frequency-doubled light;

[0055] S5: The binocular mirror separates the frequency-doubled light from the leaked Stokes light signal and outputs a narrow-linewidth visible light laser.

[0056] In step S1, the first preset power and the first preset wavelength of the pump light are both tunable;

[0057] In step S2, the coupled pump light passes through the input mirror 4 and enters the diamond crystal 5 and is focused at the center of the diamond crystal 5. The pump beam waist radius is 42 μm. The efficiency of the focused pump light is improved, and non-target band light can be easily filtered out. The frequency is ω P The pump light excites the ground state atoms of the diamond crystal 5 to the virtual Raman upper energy level and generates a frequency of ω S A Raman photon with a frequency of ω R Optical phonons, and satisfy ω P =ω S +ω R , the Raman frequency shift of diamond crystal 5 is set to 1332 cm -1 , when the pump light wavelength is 1.02-1.08μm, the excited Stokes light wavelength is 1.18-1.26μm;

[0058] In step S2, the Stokes light oscillates in a Raman oscillator composed of an input mirror 4, a reflective blazed grating 6 and an output mirror 7. The Raman wavelength is precisely adjusted by adjusting the angle of the reflective blazed grating 6. When the reflective blazed grating 6 rotates 0.00635 mrad and the Stokes center wavelength is 1240 nm, its wavelength range changes to 0.01 nm; when the reflective blazed grating 6 rotates 0.0319 mrad, the wavelength changes to 0.05 nm; and when the reflective blazed grating 6 rotates 0.0638 mrad, the wavelength changes to 0.1 nm.

[0059] In step S3, after the Stokes light is output through the output mirror 7, under the action of the shaping lens group 8, the beam size matches the beam size in the locked cavity frequency doubler 9, which greatly improves the conversion efficiency.

[0060] Therefore, the present invention adopts the above-mentioned narrow linewidth tunable Raman laser and emission method, reduces the demand for optical isolators, improves the stability of the laser resonant cavity, reduces the loss during transmission, achieves wavelength adjustment accurate to 0.01nm, and reduces the linewidth of the output optical signal, thereby achieving a narrow linewidth 0.59-0.63μm tunable wavelength output.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the method scheme of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary method personnel in the field should understand that they can still modify or replace the method scheme of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified method scheme to deviate from the spirit and scope of the method scheme of the present invention.

Claims

1. A narrow linewidth tunable Raman laser, characterized in that: It includes a half wave plate and a pump source and a focusing lens respectively arranged on both sides of the half wave plate, a laser resonant cavity is arranged on the other side of the focusing lens, a cavity-locked frequency doubler is arranged on the other side of the laser resonant cavity, a shaping lens group is arranged between the laser resonant cavity and the cavity-locked frequency doubler, a binocular mirror is arranged on the other side of the cavity-locked frequency doubler, the laser resonant cavity is arranged as a V-shaped cavity structure composed of an input mirror, an output mirror and a reflective blazed grating, a diamond crystal is arranged between the input mirror and the output mirror, and the reflective blazed grating is arranged below the diamond crystal.

2. A narrow linewidth tunable Raman laser according to claim 1, characterized in that: The locked cavity frequency multiplier includes a frequency doubling crystal and a second locked cavity reflector and a locked cavity output mirror symmetrically arranged on both sides of the frequency doubling crystal, a locked cavity input mirror is arranged above the second locked cavity reflector, a first locked cavity reflector is arranged above the locked cavity output mirror, and the locked cavity input mirror and the first locked cavity reflector are symmetrically arranged according to the frequency doubling crystal.

3. The narrow linewidth tunable Raman laser according to claim 1, characterized in that: The shaping lens group includes two convex lenses, and the surfaces of the two convex lenses are coated with a broadband dielectric film with high transmittance to Stokes light. The wavelength range of the Stokes light is set to 1.18-1.26 μm.

4. The narrow linewidth tunable Raman laser according to claim 1, characterized in that: The surface of the focusing lens is coated with a broadband dielectric film that increases the transmittance of the pump light, and the wavelength range of the pump light is set to 1.02-1.08 μm. The surface of the binocular mirror is coated with a broadband dielectric film that has high reflection for Stokes light and high transmission for doubled frequency light, and the wavelength range of the Stokes light is set to 1.18-1.26 μm, and the wavelength range of the doubled frequency light is set to 0.59-0.63 μm.

5. The narrow linewidth tunable Raman laser according to claim 1, characterized in that: The reflectivity of the input mirror and the reflectivity of the output mirror are all different from the reflectivity of the reflective blazed grating. The input mirror adopts a plano-concave reflector with a curvature radius of 50 mm. The plane of the input mirror is coated with a broadband dielectric film for enhancing the transmittance of pump light. The concave surface of the input mirror is coated with a broadband dielectric film with a reflectivity of Stokes light greater than 99.9%. The wavelength range of Stokes light is set to 1.18-1.26 μm. The output mirror adopts a plano-concave reflector with a curvature radius of 100 mm. The concave surface of the output mirror is coated with a broadband dielectric film with a reflectivity greater than 99.9% for pump light and a transmittance of 0.1%-0.5% for Stokes light, the flat surface of the output mirror is coated with a broadband dielectric film that is transmissive to Stokes light, the wavelength range of Stokes light is set to 1.18-1.26μm, the reflectivity of the reflective blazed grating is greater than 99.9%, the reflection band is set to 1.18-1.26μm, and a plurality of grating lines are arranged on the reflective blazed grating.

6. The narrow linewidth tunable Raman laser according to claim 1, characterized in that: The diamond crystal is an artificial diamond crystal cut along an axis facing a diagonal line, and the size of the diamond crystal is 7×4×1.2 mm. 3 The left and right sides of the diamond crystal are coated with broadband dielectric films with a transmittance of more than 99.5% for pump light and Stokes light. The wavelength range of the pump light is set to 1.02-1.08 μm, and the wavelength range of the Stokes light is set to 1.18-1.26 μm.

7. The narrow linewidth tunable Raman laser according to claim 2, characterized in that: The cavity lock input mirror adopts a plane reflector, the left side of the cavity lock input mirror is coated with a broadband dielectric film for enhancing the transmittance of Stokes light, and the wavelength range of Stokes light is set to 1.18-1.26μm, the right side of the cavity lock input mirror is coated with a broadband dielectric film with a transmittance of 2-4% to Stokes light, and the wavelength range of Stokes light is set to 1.18-1.26μm, the cavity lock output mirror adopts a plano-concave reflector with a curvature radius of 100mm, the concave surface of the cavity lock output mirror is coated with a broadband dielectric film with a reflectance of more than 99.9% to Stokes light and a broadband dielectric film with a transmittance of more than 90% to doubled frequency light, the wavelength range of Stokes light is set to 1.18-1.26μm, and the wavelength range of doubled frequency light is 2-4%. The range of the wavelength of the frequency-doubled light is set to 0.59-0.63 μm, the plane of the cavity-locked output mirror is coated with a broadband dielectric film with a transmittance of more than 99.5% to the frequency-doubled light, and the wavelength range of the frequency-doubled light is set to 0.59-0.63 μm, the first cavity-locked reflector adopts a plane reflector, the surface of the first cavity-locked reflector is coated with a broadband dielectric film with a reflectance of more than 99.9% to the Stokes light, and the wavelength range of the Stokes light is set to 1.18-1.26 μm, the second cavity-locked reflector adopts a plano-concave reflector with a curvature radius of 100 mm, the concave surface of the second cavity-locked reflector is coated with a broadband dielectric film with a reflectance of more than 99.9% to the Stokes light, and the wavelength range of the Stokes light is set to 1.18-1.26 μm.

8. The narrow linewidth tunable Raman laser according to claim 2, characterized in that: The frequency doubling crystal adopts LBO crystal, the cutting angle of the LBO crystal is 90°, the temperature phase of the LBO crystal is 0°, and the size of the LBO crystal is designed to be 4×4×10 mm 3 The left and right sides of the LBO crystal are coated with broadband dielectric films for enhancing the transmittance of Stokes light and frequency-doubled light. The wavelength range of Stokes light is set to 1.18-1.26 μm, and the wavelength range of frequency-doubled light is set to 0.59-0.63 μm.

9. A method for emitting a narrow linewidth tunable Raman laser according to any one of claims 1 to 8, characterized in that: The steps include: S1: The pump source emits pump light, which is coupled through a half-wave plate and a focusing lens; S2: The coupled pump light passes through the input mirror and enters the diamond crystal. The diamond crystal converts the pump light into a Stokes light signal using the SRS effect. The angle of the reflective blazed grating is adjusted to precisely adjust the wavelength. The precision adjustment range is set to [0.01-0.1] nm. S3: The Stokes optical signal passes through the output mirror and enters the shaping lens group, and the shaping lens group couples the Stokes optical signal; S4: The cavity-locked frequency doubler frequency-doubles the coupled Stokes optical signal and outputs frequency-doubled light; S5: The binocular mirror separates the frequency-doubled light from the leaked Stokes light signal and outputs a narrow-linewidth visible light laser.

10. The method for emitting a narrow linewidth tunable Raman laser according to claim 9, characterized in that: In step S1, the first preset power and the first preset wavelength of the pump light are both tunable.

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