Seed-injection based diamond Raman laser and its working method

Abstract

This invention belongs to the field of laser technology and proposes a seed-injection-based diamond Raman laser and its operating method. A single-frequency continuous-wave seed laser source is used to inject seeds into a diamond ring cavity, reducing the pump threshold of the diamond Raman laser. By changing the cavity mirror parameters of the diamond ring cavity and tuning the output wavelength of the single-frequency continuous-wave seed laser source, Raman laser output in a preset band is achieved. Based on the advantage of diamond crystal having the largest Raman frequency shift coefficient, and by combining seed injection technology with a diamond ring cavity, the pump threshold of a 2μm band laser pumping a diamond all-solid-state Raman laser is reduced. This enables the laser to achieve pulsed laser output of 2.9μm band first-order Stokes light and 4.7μm band second-order Stokes light at lower pump energies, improving the energy utilization efficiency of the laser.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, and particularly relates to a diamond Raman laser based on seed injection and its working method. Background Technology

[0002] In the field of mid-infrared lasers, pulsed lasers in the 2.9μm and 4.7μm bands have important applications in medicine, atmospheric monitoring, and spectral analysis.

[0003] All-solid-state Raman lasers pumped with diamond using a 2μm-band laser provide a new approach to extending laser coverage to the 2.9μm and 4.7μm bands. Diamond ensures the stability of the laser during high-power operation, exhibiting stable chemical properties, a high damage threshold, and the ability to withstand high-energy pump light. However, diamond suffers from a high absorption coefficient and low Raman gain in the mid-infrared band, resulting in a high pump threshold. This necessitates achieving pulsed laser output of first-order Stokes light in the 2.9μm band and second-order Stokes light in the 4.7μm band at higher pump energies, impacting the laser's energy utilization efficiency. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a seed-injection-based diamond Raman laser and its operating method. Leveraging the advantage of diamond crystals having the largest Raman frequency shift coefficient, and combining seed injection technology with a diamond ring cavity, the pump threshold of the 2μm band laser pumping the diamond all-solid-state Raman laser is reduced. This enables the laser to achieve pulsed laser output of 2.9μm band first-order Stokes light and 4.7μm band second-order Stokes light at lower pump energies, thereby improving the laser's energy utilization efficiency.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a seed-injection-based diamond Raman laser, employing the following technical solution:

[0006] A seed-injection-based diamond Raman laser includes an optical component, a pump laser source and a diamond ring cavity respectively disposed at both ends of the optical component, a helium-neon indicator light source disposed on one side of the optical component, and a single-frequency continuous light seed laser source disposed on one side of the diamond ring cavity.

[0007] The diamond annular cavity includes an input mirror near one end of the optical component, a reflecting mirror away from the optical component, and an output mirror; a diamond is disposed between the input mirror and the reflecting mirror.

[0008] A single-frequency continuous-wave seed laser source is used to inject seeds into the diamond ring cavity from the output mirror, thereby reducing the pump threshold of the diamond Raman laser. By changing the cavity mirror parameters of the diamond ring cavity and tuning the output wavelength of the single-frequency continuous-wave seed laser source, Raman laser output in a preset band can be achieved.

[0009] Furthermore, the optical components include a half-wave plate, a polarizer, a silver mirror, a plano-convex mirror, a first aperture, and a second aperture arranged sequentially along the laser emission direction.

[0010] Furthermore, the endoscope of the diamond annular cavity is mounted on the diamond annular cavity endoscope adjustment mechanism; the diamond annular cavity endoscope adjustment mechanism includes a base, a direction converter mounted on the base, an extension rod mounted on one side of the direction converter, and an endoscope frame mounted on the extension rod away from the direction converter.

[0011] Furthermore, the diamond is disposed on a diamond fixture, which is disposed on a rotary displacement stage; the diamond fixture includes a water-cooling channel and a diamond placement stage disposed on the water-cooling channel; the rotary displacement stage is disposed on a one-dimensional displacement stage, which is disposed on a pitch displacement stage.

[0012] Furthermore, the pump laser source is a 2μm band pulsed laser.

[0013] Furthermore, the incident angle between the 2μm wavelength incident light and the diamond crystal end face is 66.7°.

[0014] Furthermore, the diamond annular cavity uses along... <111> Axial cutting of diamond with Brewster angle at the end face.

[0015] Furthermore, the input mirror and the reflecting mirror are half-inch plano-concave mirrors, and the output mirror is a half-inch plane mirror.

[0016] To achieve the above objectives, in a second aspect, the present invention also provides a method for operating a diamond Raman laser based on seed injection, employing the following technical solution:

[0017] A seed-injection-based diamond Raman laser operating method, using the seed-injection-based diamond Raman laser as described in the first aspect, includes: injecting seeds into a diamond ring cavity using a single-frequency continuous-wave seed laser source to reduce the pump threshold of the diamond Raman laser; and achieving Raman laser output in a preset band by changing the cavity mirror parameters of the diamond ring cavity and tuning the output wavelength of the single-frequency continuous-wave seed laser source.

[0018] Furthermore, the parameters of the cavity mirrors in the diamond annular cavity vary with the target wavelength. When outputting signal light in the 2.9μm band, the input mirror has high transmittance and high reflectivity for the 2μm band, the reflecting mirror has high transmittance and high reflectivity for the 2.9μm band, and the output mirror has a transmittance of 2%-5% for the 2.9μm band. When outputting signal light in the 4.7μm band, the input mirror has high transmittance and high reflectivity for the 2μm band, the 2.9μm band, and the 4.7μm band, the reflecting mirror has high transmittance and high reflectivity for the 2μm band, the 2.9μm band, and the 4.7μm band, and the output mirror has a transmittance of 2%-5% for the 2.9μm band and the 4.7μm band.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention uses a single-frequency continuous-wave seed laser source to inject seeds into a diamond ring cavity, reducing the pump threshold of the diamond Raman laser. By changing the cavity mirror parameters of the diamond ring cavity and tuning the output wavelength of the single-frequency continuous-wave seed laser source, Raman laser output in a preset band can be achieved. Based on the advantage of diamond crystal having the largest Raman frequency shift coefficient, and by combining seed injection technology with a diamond ring cavity, the pump threshold of a 2μm band laser pumping a diamond all-solid-state Raman laser is reduced. This enables the laser to achieve pulsed laser output of 2.9μm band first-order Stokes light and 4.7μm band second-order Stokes light at lower pump energies, improving the energy utilization efficiency of the laser.

[0021] This invention designs a carrier based on the shape of the diamond and the characteristics of the cavity, including a water-coolable diamond clamp, a combined displacement stage, and a mirror frame. It effectively solves the problem of diamond thermal management under high-power pumping, avoiding thermal lensing effects and thermal damage; the integrated combined displacement stage enables precise adjustment of the diamond crystal position, ensuring accurate cavity construction and optimal performance; and it effectively shortens the cavity length, reduces the laser's pump threshold, and improves output power and efficiency. Attached Figure Description

[0022] The accompanying drawings, which form part of this embodiment, are used to provide a further understanding of this embodiment. The illustrative embodiments and their descriptions are used to explain this embodiment and do not constitute an improper limitation of this embodiment.

[0023] Figure 1 This is a schematic diagram of the diamond Raman laser structure according to Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the diamond annular cavity mirror adjustment mechanism according to Embodiment 1 of the present invention;

[0025] Figure 3 This is a schematic diagram of the diamond clamp according to Embodiment 1 of the present invention;

[0026] The components include: 1. Pump laser source; 2. Helium-neon indicator light source; 3. Single-frequency continuous light seed laser source; 4. Optical components; 41. Half-wave plate; 42. Polarizer; 43. Silver mirror; 44. Plano-convex mirror; 45. First aperture; 46. Second aperture; 5. Diamond annular cavity; 51. Input mirror; 52. Reflecting mirror; 53. Output mirror; 54. Diamond; 6. Diamond annular cavity mirror adjustment mechanism; 61. Mirror frame; 62. Extension rod; 63. Direction converter; 64. Base; 7. Diamond clamp; 71. Diamond placement stage; 72. Screw hole; 73. Water cooling channel; 74. Screw hole; 8. Rotary displacement stage; 9. One-dimensional displacement stage; 10. Pitch displacement stage; 11. Support column. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0029] In the field of mid-infrared lasers, pulsed lasers in the 2.9μm and 4.7μm bands have important applications in medicine, atmospheric monitoring, and spectral analysis, but currently there are limited technologies that can stably output lasers in these two bands.

[0030] Traditional mid-infrared laser output methods suffer from problems such as low efficiency, poor stability, and complex structure. For example, some gas- or semiconductor-based lasers are limited by material properties, making it difficult to achieve efficient and stable laser output in the 2.9μm and 4.7μm bands.

[0031] An all-solid-state Raman laser pumped from diamond using a 2μm-band laser provides a new approach to expanding laser coverage to the 2.9μm and 4.7μm bands. Diamond possesses numerous advantages: its extremely high thermal conductivity effectively dissipates heat, ensuring the laser's stability during high-power operation; its chemical stability and high damage threshold allow it to withstand high-energy pump light. Furthermore, diamond exhibits a large Raman gain coefficient and a Raman frequency shift of 1332 cm⁻¹. -1 It can efficiently convert 2μm pump light into first-order Stokes light (2.9μm band) and second-order Stokes light (4.7μm band).

[0032] However, diamond has a high absorption coefficient and low Raman gain in the mid-infrared band, which leads to a high pump threshold. The laser needs to achieve pulsed laser output of first-order Stokes light in the 2.9μm band and second-order Stokes light in the 4.7μm band at a high pump energy, which affects the energy utilization efficiency of the laser.

[0033] To solve the above problems, such as Figure 1 As shown, one embodiment of the present invention provides a seed-injection-based diamond Raman laser, including a pump laser source 1, a helium-neon indicator light source 2, a single-frequency continuous light seed laser source 3, optical components 4, a diamond annular cavity 5, a diamond annular cavity mirror adjustment mechanism 6, a diamond fixture 7, a rotary displacement stage 8, a one-dimensional displacement stage 9, a pitch displacement stage 10, and a support column 11, etc.

[0034] Optionally, the pump laser source 1 and the diamond annular cavity 5 are located at opposite ends of the optical component 4; the helium-neon indicator light source 2 is located on one side of the middle of the optical component 4; and the single-frequency continuous light seed laser source 3 is located on one side of the diamond annular cavity 5.

[0035] The optical component 4 includes a half-wave plate 41, a polarizer 42, a silver mirror 43, a plano-convex mirror 44, a first aperture 45, and a second aperture 46 arranged sequentially along the laser emission direction. The diamond annular cavity 5 includes an input mirror 51 near one end of the optical component 4, a reflecting mirror 52 away from the other end of the optical component 4, and an output mirror 53; a diamond 54 is disposed between the input mirror 51 and the reflecting mirror 52.

[0036] like Figure 2 As shown, the diamond annular cavity endoscope adjustment mechanism 6 includes a base 64, a direction converter 63 mounted on the base 64, an extension rod 62 mounted on one side of the direction converter 63, and an endoscope frame 61 mounted on the extension rod 62 away from the direction converter 63. The direction converter 63 can move up and down and rotate left and right along the base 64. The direction converter 63 can be implemented using conventional technology and will not be described in detail here. The endoscope frame 61 is used to hold the endoscope of the diamond annular cavity. During operation, the diamond annular cavity endoscope adjustment mechanism 6 can adjust the pump light to pass through the center of the endoscope mounted on the endoscope frame 61, and make the endoscope close to the diamond clamp.

[0037] like Figure 3As shown, the diamond clamp 7 includes a water-cooling channel 73 and a diamond placement platform 71 disposed on the water-cooling channel 73; the diamond placement platform 71 can be detachably mounted with clamping blocks via screw holes 74 and screws; the diamond clamp 7 is also provided with screw holes 72 (threaded holes) for fixing to the rotary displacement stage 8. The rotary displacement stage 8 is disposed on a one-dimensional displacement stage 9, and the one-dimensional displacement stage 9 is disposed on a pitch displacement stage 10. The lower end of the pitch displacement stage 10 is provided with a support column 11; the rotary displacement stage 8 can achieve rotation in the horizontal direction, the one-dimensional displacement stage 9 can achieve movement in the horizontal direction, and the pitch displacement stage 10 can achieve pitch angle adjustment; the rotary displacement stage 8, the one-dimensional displacement stage 9, and the pitch displacement stage 10 can all be implemented using conventional technology, which will not be described in detail here.

[0038] The pump laser source 1 can be a 2μm band pulsed laser for emitting pump laser; the helium-neon indicator light source 2 is used to assist in building the laser system.

[0039] When setting up the laser system, firstly, the pump laser source 1 is turned off. The indicator light is collimated using a helium-neon indicator light source 2, along with a silver mirror 43, a plano-convex mirror 44, a first aperture 45, and a second aperture 46. Then, using the helium-neon indicator light source 2, based on the principle of light reversibility, the position and angle of the diamond ring cavity 5 mirror and the position and angle of the diamond ring cavity 54 are adjusted via the diamond ring cavity mirror adjustment mechanism 6 to complete the construction of the diamond ring cavity 5. Next, the silver mirror 43 is moved out of the optical path via a rotating mirror mount, and the pump laser source 1 is turned on. By rotating the half-wave plate 41 and adjusting the position of the polarizer 42, the polarization state of the pump light is adjusted to a p-polarization state. Finally, the pump light and the indicator light optical paths are aligned using the plano-convex mirror 44, the first aperture 45, and the second aperture 46. Then, a seed is injected into the diamond ring cavity 5 using a single-frequency continuous light seed laser source 3 to reduce the pump threshold of the diamond Raman laser. Finally, by changing the cavity mirror parameters of the diamond ring cavity 5 and tuning the output wavelength of the single-frequency continuous light seed laser source 3, a first-order Stokes light in the 2.9μm band or a second-order Stokes light in the 4.7μm band can be used as the Raman laser output.

[0040] Optionally, the pump laser source 1 is a Ho:YAG laser. The diamond ring cavity 5 reduces the pump threshold by combining single-frequency continuous seed light injection with the ring cavity. The single-frequency continuous seed laser source 3 is an MgO:PPLN laser with a tunable output wavelength ranging from 2μm to 5μm. The diamond ring cavity 5... <111> Axial cutting of diamond 54 with Brewster angle at the end face, effective length of 5mm.

[0041] Specifically, in the field of nonlinear frequency conversion, optical crystals need to be coated with antireflective films of corresponding optical bands on the incident and exit surfaces to improve transmittance and reduce the pump threshold. Diamond 54 has a high intrinsic absorption coefficient in the 2.5μm to 6μm band, resulting in a high pump threshold. Therefore, a high-power laser is required as the pump source. However, the film layer on the crystal end face cannot withstand this and is easily damaged. Diamond 54 with Brewster angle-cut end face can have high transmittance for p-polarized light. After testing, the transmittance of p-polarized pump light in the 2μm band incident on diamond 54 at an incident angle of 66.7° can reach 98%. Therefore, by adjusting the incident light to be p-polarized and incident on diamond 54 with Brewster angle-cut end face, the problem of low damage threshold of the antireflective film can be avoided, and the pump power of the overall resonant cavity can be improved.

[0042] Optionally, diamond 54 crystals are used in... <111> The Raman gain is highest along the axis, therefore the pump light along... <111> Axial incidence. The plano-convex mirror 44 has a focal length of 100mm or 75mm and is coated with a 2μm band antireflective film, reducing the waist radius of the pump beam to 50-100μm, and placing the diamond crystal 5-4 at the focal point. The incident angle between the 2μm band pump light and the end face of the diamond 54 crystal is 66.7°.

[0043] Specifically, in the laser system, the pump light is first adjusted to a p-polarized state, and then directed along the diamond 54 crystal. <111> The beam is focused and incident at an angle of 66.7°, with the beam waist radius at the focal point being 50 μm.

[0044] Optionally, the input mirror 51 and the reflecting mirror 52 used in the diamond annular cavity 5 (cavity mirror) are half-inch plano-concave mirrors, and the output mirror 53 is a half-inch plane mirror; the cavity mirror of the diamond annular cavity is placed in the mirror holder 61 and connected to the direction conversion base.

[0045] Specifically, the length of the diamond Raman cavity has a significant impact on the pump threshold. Shortening the cavity length can effectively reduce the pump threshold. Therefore, in this system, the cavity mirror size is half an inch, and a frame 61 is designed. The frame 61 is connected to the direction converter 63 through the extension rod 62. It can be in a semi-suspended state and closely attached to the diamond clamp 7, avoiding the extra distance caused by the size of the optical device base when building the optical path. It can be as close as possible to the diamond clamp 7 and shorten the cavity length.

[0046] In this invention, the diamond 54 is placed in the diamond fixture 7 equipped with the water-cooling channel 73.

[0047] Specifically, in order to prevent the diamond 54 crystal from being thermally damaged due to excessively high incident power density of pump light in the experiment, a water-cooled diamond fixture 7 was designed. The diamond placement stage 71 of the fixture is the same shape as the diamond crystal, which can prevent the incident light and output light from being blocked.

[0048] In this invention, the diamond clamp 7 is placed on a combined displacement platform consisting of a rotary displacement stage 8, a one-dimensional displacement stage 9, a pitch displacement stage 10, and a support column 11.

[0049] Specifically, diamond 54 is placed on diamond placement stage 71 and the whole assembly is placed on combined displacement stage. Using helium-neon indicator light source 2, relying on the principle of light reversibility, the position of diamond 54 in the optical path, diamond pitch angle, and incident angle of pump light are adjusted through combined displacement stage to realize the construction of diamond annular cavity 5.

[0050] In this invention, the parameters of the cavity mirror in the diamond annular cavity 5 change with the target wavelength.

[0051] Specifically, when outputting 2.9μm band signal light, input mirror 51 has high transmittance for 2μm band light and high reflectivity for 2.9μm band light; reflector 52 has high transmittance for 2μm band light and high reflectivity for 2.9μm band light; and output mirror 53 has a transmittance of 2% for 2.9μm band light. When outputting 4.7μm band signal light, input mirror 51 has high transmittance for 2μm band light and high reflectivity for 2.9μm band light and 4.7μm band light; reflector 52 has high transmittance for 2μm band light and high reflectivity for 2.9μm band light and 4.7μm band light; and output mirror 53 has a transmittance of 2% for 2.9μm band light and 2% for 4.7μm band light.

[0052] Based on the seed-injection-based diamond Raman laser, one embodiment of the present invention also provides a method for operating the seed-injection-based diamond Raman laser, including: injecting seeds into a diamond ring cavity using a single-frequency continuous-wave seed laser source to reduce the pump threshold of the diamond Raman laser; and achieving Raman laser output in a preset band by changing the cavity mirror parameters of the diamond ring cavity and tuning the output wavelength of the single-frequency continuous-wave seed laser source.

[0053] The above description is merely a preferred embodiment of this practice and is not intended to limit the scope of this practice. Various modifications and variations can be made to this practice by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this practice should be included within the protection scope of this practice.

Claims

1. A diamond Raman laser based on seed injection, characterized in that, The optical assembly, a pump laser source and a diamond ring cavity arranged at two ends of the optical assembly respectively, a helium-neon indicating light source arranged at one side of the optical assembly, and a single-frequency continuous light seed laser source arranged at one side of the diamond ring cavity; The diamond ring cavity comprises an input mirror close to one end of the optical assembly, a reflecting mirror away from one end of the optical assembly, and an output mirror; a diamond is arranged between the input mirror and the reflecting mirror; The single-frequency continuous light seed laser source is used to inject seed into the diamond ring cavity, so as to reduce the pump threshold of the diamond Raman laser; by changing the cavity mirror parameters of the diamond ring cavity and tuning the output wavelength of the single-frequency continuous light seed laser source, the first-order Stokes light in the 2.9 μm wave band and the second-order Stokes light in the 4.7 μm wave band are realized.

2. The seed injection based diamond Raman laser of claim 1, wherein, The optical assembly comprises, in sequence along the laser emission direction, a half-wave plate, a polarizer, a silver mirror, a plano-convex mirror, a first diaphragm and a second diaphragm.

3. The seed injection based diamond Raman laser of claim 1, wherein, The cavity mirror of the diamond ring cavity is arranged on a diamond ring cavity mirror adjusting mechanism; the diamond ring cavity mirror adjusting mechanism comprises a base, a direction converter arranged on the base, an extension rod arranged at one side of the direction converter, and a mirror frame arranged at one end of the extension rod away from the direction converter.

4. The seed injection based diamond Raman laser of claim 1, wherein, The diamond is arranged on a diamond clamp, and the diamond clamp is arranged on a rotary displacement table; the diamond clamp comprises a water cooling channel and a diamond placing table arranged on the water cooling channel; the rotary displacement table is arranged on a one-dimensional displacement table, and the one-dimensional displacement table is arranged on a pitch displacement table.

5. The seed injection based diamond Raman laser of claim 1, wherein, The pump laser source is a 2 μm wave band pulse laser.

6. The seed injection based diamond Raman laser of claim 5, wherein, The incident angle of the 2 μm wave band incident light and the end face of the diamond crystal is 66.7°.

7. The seed injection based diamond Raman laser of claim 1, wherein, The diamond used in the diamond ring cavity is cut along the <111> axis, and the end face cut angle is the Brewster angle.

8. The seed injection based diamond Raman laser as claimed in claim 1, wherein, The input mirror and the reflecting mirror are half-inch plano-concave mirrors, and the output mirror is a half-inch plane mirror.

9. A method of operating a diamond Raman laser based on seed injection, characterized in that, The seed injection based diamond Raman laser as claimed in any one of claims 1-8 is used, including: using the single-frequency continuous light seed laser source to inject seed into the diamond ring cavity, so as to reduce the pump threshold of the diamond Raman laser; by changing the cavity mirror parameters of the diamond ring cavity and tuning the output wavelength of the single-frequency continuous light seed laser source, the first-order Stokes light in the 2.9 μm wave band and the second-order Stokes light in the 4.7 μm wave band are realized.

10. The seed injection based diamond Raman laser operating method of claim 9, wherein, The cavity mirror parameters in the diamond ring cavity change with the target wavelength; when the 2.9 μm wave band signal light is output, the input mirror is high-transmissive to the 2 μm wave band light and high-reflective to the 2.9 μm wave band light, the reflecting mirror is high-transmissive to the 2 μm wave band light and high-reflective to the 2.9 μm wave band light, and the output mirror has a transmittance of 2%-5% to the 2.9 μm wave band; when the 4.7 μm wave band signal light is output, the input mirror is high-transmissive to the 2 μm wave band light, high-reflective to the 2.9 μm wave band light, and high-reflective to the 4.7 μm wave band light, the reflecting mirror is high-transmissive to the 2 μm wave band light, high-reflective to the 2.9 μm wave band light, and high-reflective to the 4.7 μm wave band light, and the output mirror is high-reflective to the 2.9 μm wave band light and has a transmittance of 2%-5% to the 4.7 μm wave band.

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