Tunable narrow-linewidth diamond Raman laser and emission method

Abstract

The invention discloses a tunable narrow-linewidth diamond Raman laser and an emission method, and relates to the field of all-solid-state visible light lasers, the tunable narrow-linewidth diamond Raman laser comprises a coupling lens group, pumping sources and a V-shaped cavity, the pumping sources and the V-shaped cavity are respectively arranged at two sides of the coupling lens group, and a second plane concave lens is arranged at the top end of the V-shaped cavity; an F-P etalon, a laser crystal and a first plano-concave lens are sequentially arranged on the left side of the second plano-concave lens in the opening direction of the V-shaped cavity, a dichroscope, a Raman frequency doubling module and a low-pass filter are sequentially arranged below the second plano-concave lens in the opening direction of the V-shaped cavity, and the Raman frequency doubling module comprises a diamond crystal, an LBO frequency doubling crystal and a third plano-concave lens. The diamond crystal is arranged on the side close to the dichroscope, the third plane-concave lens is arranged on the side close to the low-pass filter, wavelength tuning in a wide range is achieved through tiny angle adjustment, meanwhile, the line width is compressed to achieve tuning of narrow-line-width visible light output, and the stability and reliability of the system are improved.

Description

[0001] Methodology Area

[0002] The invention relates to the field of all-solid-state visible light lasers, and in particular to a tunable narrow-linewidth diamond Raman laser and an emission method.

[0003] Background Methods

[0004] Traditional all-solid-state visible light lasers are devices that achieve laser emission through solid-state gain media and are widely used in optical communications, spectroscopy, medical treatment, industrial processing, display technology and other fields;

[0005] Laser diodes are usually used as pump sources to provide optical pumping energy to excite rare earth ions in the gain medium to achieve laser amplification. Nonlinear crystals can be used to double the fundamental frequency light to obtain visible light output. Optical parametric oscillators can also be used to split the pump light into two lights of different frequencies to produce tunable visible light output.

[0006] However, in previous linear cavity structures, the spot profile degraded early, and due to the simple optical path of the linear cavity, it was easily affected by external vibrations and environmental changes, resulting in poor frequency stability. At the same time, the longitudinal mode selectivity of the linear cavity was poor, which easily led to multi-longitudinal mode output, affecting the output spectral purity. In addition, traditional all-solid-state visible light lasers usually have wide linewidth, poor frequency stability, and are susceptible to environmental influences. Due to the characteristics of the gain medium and the frequency doubling crystal, the tuning range is difficult to cover a wide wavelength range. The thermal effect is significant during high-power operation and is easily affected by the thermal effect, resulting in a significant decrease in laser beam quality, deterioration of the optical mode and beam quality factor, and the occurrence of frequency drift and reduced efficiency. It is difficult to achieve stable output of high power and high beam quality.

[0007] Therefore, a tunable narrow-linewidth diamond Raman laser and an emission method are provided to solve the above problems. Summary of the invention

[0008] The purpose of the present invention is to provide a tunable narrow-linewidth diamond Raman laser and an emission method, which can achieve wavelength tuning in a wider range by adjusting a small angle, and simultaneously compress the linewidth to achieve tuned narrow-linewidth visible light output, thereby improving the stability and reliability of the system.

[0009] To achieve the above-mentioned purpose, the present invention provides a tunable narrow-linewidth diamond Raman laser, comprising a coupling lens group and a pump source and a V-shaped cavity respectively arranged on both sides of the coupling lens group, a second plano-concave mirror is arranged at the top of the V-shaped cavity, an FP etalon, a laser crystal and a first plano-concave mirror are arranged in sequence on the left side of the second plano-concave mirror along the opening direction of the V-shaped cavity, a dichroic mirror, a Raman frequency doubling module and a low-pass filter are arranged in sequence below the second plano-concave mirror along the opening direction of the V-shaped cavity, the Raman frequency doubling module comprises a diamond crystal, an LBO frequency doubling crystal and a third plano-concave mirror, the diamond crystal is arranged on a side close to the dichroic mirror, and the third plano-concave mirror is arranged on a side close to the low-pass filter.

[0010] Preferably, the coupling lens group includes a first convex lens and a second convex lens.

[0011] Preferably, the laser crystal is set to Nd:YVO 4 Crystal, Nd:YVO 4 The crystal is a uniaxial birefringent crystal, Nd:YVO 4 The output of the crystal is linearly polarized light, Nd:YVO 4 The left and right end faces of the crystal are coated with AR coatings with a reflectivity of less than 0.5% for 808nm light and 1050nm-1080nm light.

[0012] Preferably, the FP etalon includes two parallel reflecting surfaces, and the transmittance T of the reflecting surfaces is expressed as:

[0013]

[0014] Where R is the reflectivity of the coating, d is the thickness of the reflecting surface, and θ is the reflection angle. The light that forms stable interference between the two reflecting surfaces meets the following conditions:

[0015] mλ=2ndcosθ

[0016] Where m is the interference fringe number, λ is the wavelength of the light wave, and n is the refractive index of the transmission medium.

[0017] Preferably, the thickness of the FP etalon is set to 0.1 mm, the coating reflectivity is set to 35%, the initial angle is set to 0.55 rad, the angle adjustment range is set to 0.4 rad-0.6 rad, and the wavelength tuning range is 1050.74 nm-1076.83 nm.

[0018] Preferably, the plane of the first plano-concave mirror is coated with an AR coating having a reflectivity of less than 0.5% for 808nm light, the concave surface of the first plano-concave mirror is coated with an HR coating having a reflectivity of greater than 99% for 1050nm-1080nm light, the surface of the second plano-concave mirror is coated with an HR coating having a reflectivity of greater than 99% for 1050nm-1080nm light and 1220nm-1260nm light, the surface of the dichroic mirror is coated with an AR coating having a reflectivity of less than 0.5% for 1050nm-1080nm light and an HR coating having a reflectivity of greater than 99% for 1220nm-1260nm light, the surface of the third plano-concave mirror is coated with an HR coating having a reflectivity of greater than 99% for 1050nm-1080nm light and 1220nm-1260nm light, and the transmittance of the third plano-concave mirror to 610nm-630nm light is 0.6%.

[0019] Preferably, the size of the diamond crystal is set to 2×2×7 mm3, and both ends of the diamond crystal are respectively coated with AR coatings with a reflectivity of less than 0.5% for 1050nm-1080nm light and 1220nm-1260nm light.

[0020] Preferably, the cutting angle of the LBO frequency doubling crystal is set to θ=85.8°, φ=0°, and both ends of the LBO frequency doubling crystal are respectively coated with AR coatings with a reflectivity of less than 0.5% for 1220nm-1260nm light and 610nm-630nm light.

[0021] Preferably, a method for emitting a tunable narrow linewidth diamond Raman laser comprises the following steps:

[0022] S1: The pump source emits pump light with a wavelength of 808 nm. The first convex lens and the second convex lens optimize the output of the pump light. The first plano-concave mirror focuses the pump light onto the laser crystal.

[0023] S2: The laser crystal converts the pump light into fundamental frequency light with a wavelength of 1064nm;

[0024] S3: The fundamental frequency light enters the FP etalon, which tunes the fundamental frequency light and compresses the line width of the fundamental frequency light.

[0025] S4: the second plano-concave mirror reflects the fundamental frequency light to the dichroic mirror, the dichroic mirror reflects the fundamental frequency light to the Raman conversion module, and the Raman conversion module performs a frequency doubling operation on the fundamental frequency light;

[0026] S5: The frequency-doubled light enters the low-pass filter, which filters out the pump light and Stokes light in the frequency-doubled light and outputs pure frequency-doubled light.

[0027] Preferably, in step S4, the Raman conversion module performs a frequency doubling operation on the fundamental frequency light, specifically comprising the following steps:

[0028] S41: The fundamental frequency light enters the diamond crystal, and the diamond crystal performs Raman conversion on the fundamental frequency light, outputting Raman light with a wavelength between 1221.73nm and 1257.15nm;

[0029] S42: The Raman light enters the LBO frequency doubling crystal, and the LBO frequency doubling crystal doubles the frequency of the Raman light to output a frequency doubling light with a wavelength between 610.87nm and 628.58nm.

[0030] Therefore, the present invention adopts a tunable narrow linewidth diamond Raman laser and an emission method of the above structure, which has the following beneficial effects:

[0031] (1) The laser of the present invention uses CVD (chemical vapor deposition) grown single crystal diamond as the Raman gain medium. Diamond has a high Raman gain coefficient, a large Raman frequency shift and extremely high thermal conductivity, which improves the stability and reliability of the system and can achieve high beam quality Raman light output;

[0032] (2) The present invention adopts a V-shaped Raman cavity structure. Compared with a linear cavity, the V-shaped cavity has higher conversion efficiency and stability. The V-shaped cavity structure allows for more flexible adjustment of the optical path length, which is very helpful for achieving precise wavelength tuning. At the same time, the V-shaped cavity is easier to achieve mode selection, helps reduce unnecessary mode competition, enhances the stability of the main laser mode, helps optimize the beam quality, and improves the collimation and spot quality of the output beam;

[0033] (3) The present invention can precisely control the wavelength loss by adjusting the angle of the FP etalon, thereby achieving precise wavelength tuning. By slightly changing the angle, wavelength tuning within a wide range can be achieved. This method is highly flexible and can adapt to different wavelength requirements and meet the needs of different experiments. In addition, the FP etalon can also be used to achieve linewidth compression. The narrow linewidth laser output helps to reduce spectral noise and improve the signal-to-noise ratio, which is of great significance for applications such as precision measurement.

[0034] The method scheme of the present invention is further described in detail below through the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a structural diagram of a tunable narrow-linewidth diamond Raman laser of the present invention.

[0036] Among them: 1. Pump source; 2. First convex lens; 3. Second convex lens; 4. First plano-concave mirror; 5. Laser crystal; 6. FP etalon; 7. Second plano-concave mirror; 8. Dichroic mirror; 9. Diamond crystal; 10. LBO frequency doubling crystal; 11. Third plano-concave mirror; 12. Low-pass filter. DETAILED DESCRIPTION

[0037] The method scheme of the present invention is further described below through drawings and embodiments.

[0038] 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.

[0039] 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.

[0040] Example

[0041] like Figure 1 As shown, the present invention provides a tunable narrow linewidth diamond Raman laser, including a coupling lens group and a pump source 1 respectively arranged on both sides of the coupling lens group, and a V-shaped cavity. The V-shaped cavity structure can effectively alleviate the thermal effect, has higher efficiency and better beam quality, and because there are multiple reflection and refraction paths in the optical path, the influence of the environment on the light field in the cavity can be effectively reduced, and the frequency stability can be improved. In addition, the V-shaped cavity design is relatively compact, and a specific resonance mode can be selected by adjusting the reflector to achieve single longitudinal mode output and improve spectral purity.

[0042] A second plano-concave mirror 7 is arranged at the top of the V-shaped cavity, and an FP etalon 6, a laser crystal 5 and a first plano-concave mirror 4 are arranged in sequence on the left side of the second plano-concave mirror 7 along the opening direction of the V-shaped cavity. A dichroic mirror 8, a Raman frequency doubling module and a low-pass filter 12 are arranged in sequence below the second plano-concave mirror 7 along the opening direction of the V-shaped cavity. The Raman frequency doubling module includes a diamond crystal 9, an LBO frequency doubling crystal 10 and a third plano-concave mirror 11. The diamond crystal 9 is arranged on a side close to the dichroic mirror 8, and the third plano-concave mirror 11 is arranged on a side close to the low-pass filter 12.

[0043] The coupling lens group includes a first convex lens 2 and a second convex lens 3, which refocus the pump light into the laser crystal 5 to optimize the transmission and focusing of the pump light. The first convex lens 2 and the second convex lens 3 improve the pump efficiency and laser output performance by adjusting the spot size of the pump light, ensuring that the pump energy can be evenly distributed in the laser crystal 5, thereby improving the performance of the laser and ensuring the efficient and stable operation of the laser. In addition, focusing can improve the divergence angle of the pump light beam, thereby increasing the energy density of the pump light.

[0044] Laser crystal 5 is set to Nd:YVO 4 Crystal, Nd:YVO 4 The crystal is a uniaxial birefringent crystal, Nd:YVO 4 The output of the crystal is linearly polarized light, Nd:YVO 4 The left and right end faces of the crystal are coated with AR coatings with a reflectivity of less than 0.5% for 808nm light and 1050nm-1080nm light. Compared with Nd:YAG crystals, Nd:YVO 4 The crystal has a higher absorption coefficient and a larger stimulated emission cross section for pump light, a lower laser threshold and a higher slope efficiency.

[0045] The FP etalon 6 includes two parallel reflective surfaces. When light enters the FP etalon 6, it will be reflected and interfered multiple times between the two reflective surfaces. The transmittance T of the reflective surface is expressed as:

[0046]

[0047] Where R is the reflectivity of the coating, d is the thickness of the reflecting surface, and θ is the reflection angle. The light that forms stable interference between the two reflecting surfaces meets the following conditions:

[0048] mλ=2ndcosθ

[0049] Where m is the interference fringe number, λ is the wavelength of the light wave, and n is the refractive index of the transmission medium.

[0050] The thickness of the two reflecting surfaces is set to 0.1 mm, the coating reflectivity is set to 35%, the initial angle is set to 0.55 rad, the angle adjustment range is set to 0.4 rad-0.6 rad, and the wavelength tuning range is set to 1050.74 nm-1076.83 nm. By precisely adjusting the angle of the FP etalon 6, precise control of the laser output wavelength can be achieved. In addition, compared with other methods, such as using different filters, the FP etalon 6 can achieve continuous wavelength tuning.

[0051] The plane surface of the first plano-concave mirror 4 is coated with an AR coating with a reflectivity of less than 0.5% for 808nm light, the concave surface of the first plano-concave mirror 4 is coated with an HR coating with a reflectivity of more than 99% for 1050nm-1080nm light, the surface of the second plano-concave mirror 7 is coated with an HR coating with a reflectivity of more than 99% for 1050nm-1080nm light and 1220nm-1260nm light, the surface of the dichroic mirror 8 is coated with an AR coating with a reflectivity of less than 0.5% for 1050nm-1080nm light and an HR coating with a reflectivity of more than 99% for 1220nm-1260nm light, the surface of the third plano-concave mirror 11 is coated with an HR coating with a reflectivity of more than 99% for 1050nm-1080nm light and 1220nm-1260nm light, and the transmittance of the third plano-concave mirror 11 to 610nm-630nm light is 0.6%.

[0052] The size of the diamond crystal 9 is set to 2×2×7 mm 3 Both ends of the diamond crystal 9 are respectively coated with AR coatings with a reflectivity of less than 0.5% for 1050nm-1080nm light and 1220nm-1260nm light. Diamond is used as a Raman gain medium, which has a higher Raman gain coefficient, a larger Raman frequency shift, a relatively narrow Raman linewidth, a wider spectral transmission range and extremely high thermal conductivity, which reduces the influence of thermal effects on laser performance, improves the stability and reliability of the system, and can achieve high beam quality Raman light output.

[0053] The cutting angle of the LBO frequency doubling crystal 10 is set to θ=85.8°, φ=0°, and both ends of the LBO frequency doubling crystal 10 are respectively plated with AR coatings with a reflectivity of less than 0.5% for 1220nm-1260nm light and 610nm-630nm light.

[0054] A method for emitting a tunable narrow-linewidth diamond Raman laser comprises the following steps:

[0055] S1: The pump source emits pump light with a wavelength of 808 nm. The first convex lens and the second convex lens optimize the output of the pump light. The first plano-concave mirror focuses the pump light onto the laser crystal.

[0056] S2: The laser crystal converts the pump light into fundamental frequency light with a wavelength of 1064nm;

[0057] S3: The fundamental frequency light enters the FP etalon, which tunes the fundamental frequency light and compresses the line width of the fundamental frequency light.

[0058] S4: the second plano-concave mirror reflects the fundamental frequency light to the dichroic mirror, the dichroic mirror reflects the fundamental frequency light to the Raman conversion module, and the Raman conversion module performs a frequency doubling operation on the fundamental frequency light;

[0059] In step S4, the Raman conversion module performs a frequency doubling operation on the fundamental frequency light, which specifically includes the following steps:

[0060] S41: The fundamental frequency light enters the diamond crystal, and the diamond crystal performs Raman conversion on the fundamental frequency light, outputting Raman light with a wavelength between 1221.73nm and 1257.15nm;

[0061] Raman conversion is a third-order nonlinear effect. The incident strong light photons interact with the atoms or molecules inside the medium, generating Stokes photons with a certain frequency shift and being continuously amplified, which is a nonlinear process that suppresses other weaker Raman modes. During the Raman conversion process, there will be an obvious beam purification effect, which significantly improves the output beam quality.

[0062] S42: The Raman light enters the LBO frequency doubling crystal, which doubles the frequency of the Raman light and outputs frequency doubling light with a wavelength between 610.87nm and 628.58nm.

[0063] S5: The frequency-doubled light enters the low-pass filter, which filters out the pump light and Stokes light in the frequency-doubled light and outputs pure frequency-doubled light.

[0064] Therefore, the present invention adopts the above-mentioned tunable narrow-linewidth diamond Raman laser and emission method, adjusts the FP standard tool angle within the range of 0.4rad-0.6rad, realizes the tunability of the fundamental frequency light 1050.74nm-1076.83nm light, uses the diamond crystal as the Raman gain medium to generate 1221.73nm-1257.15nm Raman light, and combines with the LBO frequency doubling crystal to realize 610.87nm-628.58nm frequency doubling light output.

[0065] 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 tunable narrow linewidth diamond Raman laser, characterized in that: The invention comprises a coupling lens group and a pump source and a V-shaped cavity respectively arranged on both sides of the coupling lens group. A second plano-concave mirror is arranged at the top of the V-shaped cavity. An FP standard tool, a laser crystal and a first plano-concave mirror are arranged in sequence on the left side of the second plano-concave mirror along the opening direction of the V-shaped cavity. A dichroic mirror, a Raman frequency doubling module and a low-pass filter are arranged in sequence below the second plano-concave mirror along the opening direction of the V-shaped cavity. The Raman frequency doubling module comprises a diamond crystal, an LBO frequency doubling crystal and a third plano-concave mirror. The diamond crystal is arranged on a side close to the dichroic mirror, and the third plano-concave mirror is arranged on a side close to the low-pass filter.

2. The tunable narrow linewidth diamond Raman laser according to claim 1, characterized in that: The coupling lens group includes a first convex lens and a second convex lens.

3. The tunable narrow linewidth diamond Raman laser according to claim 1, characterized in that: The laser crystal is set as Nd:YVO4 crystal, which is a uniaxial birefringent crystal. The output of Nd:YVO4 crystal is linearly polarized light. The left and right end faces of Nd:YVO4 crystal are coated with AR coating with a reflectivity of less than 0.5% for 808nm light and 1050nm-1080nm light.

4. The tunable narrow linewidth diamond Raman laser according to claim 1, characterized in that: The FP etalon includes two parallel reflective surfaces, and the transmittance T of the reflective surfaces is expressed as: Where R is the reflectivity of the coating, d is the thickness of the reflecting surface, and θ is the reflection angle. The light that forms stable interference between the two reflecting surfaces meets the following conditions: mλ=2ndcosθ Where m is the interference fringe number, λ is the wavelength of the light wave, and n is the refractive index of the transmission medium.

5. The tunable narrow linewidth diamond Raman laser according to claim 4, characterized in that: The thickness of the FP etalon is set to 0.1 mm, the coating reflectivity is set to 35%, the initial angle is set to 0.55 rad, the angle adjustment range is set to 0.4 rad-0.6 rad, and the wavelength tuning range is 1050.74 nm-1076.83 nm.

6. The tunable narrow linewidth diamond Raman laser according to claim 1, characterized in that: The plane surface of the first plano-concave mirror is coated with an AR coating with a reflectivity of less than 0.5% for 808nm light, the concave surface of the first plano-concave mirror is coated with an HR coating with a reflectivity of more than 99% for 1050nm-1080nm light, the surface of the second plano-concave mirror is coated with an HR coating with a reflectivity of more than 99% for 1050nm-1080nm light and 1220nm-1260nm light, the surface of the dichroic mirror is coated with an AR coating with a reflectivity of less than 0.5% for 1050nm-1080nm light and an HR coating with a reflectivity of more than 99% for 1220nm-1260nm light, the surface of the third plano-concave mirror is coated with an HR coating with a reflectivity of more than 99% for 1050nm-1080nm light and 1220nm-1260nm light, and the transmittance of the third plano-concave mirror to 610nm-630nm light is 0.6%.

7. The tunable narrow linewidth diamond Raman laser according to claim 1, characterized in that: The size of the diamond crystal is set to 2×2×7mm 3 , both ends of the diamond crystal are respectively coated with AR coatings with a reflectivity of less than 0.5% for 1050nm-1080nm light and 1220nm-1260nm light.

8. The tunable narrow linewidth diamond Raman laser according to claim 1, characterized in that: The cutting angle of the LBO frequency doubling crystal is set to θ=85.8°, φ=0°, and both ends of the LBO frequency doubling crystal are respectively plated with AR coatings with a reflectivity of less than 0.5% for 1220nm-1260nm light and 610nm-630nm light.

9. A method for emitting a tunable narrow linewidth diamond Raman laser according to any one of claims 1 to 8, characterized in that: The steps include: S1: The pump source emits pump light with a wavelength of 808 nm. The first convex lens and the second convex lens optimize the output of the pump light. The first plano-concave mirror focuses the pump light onto the laser crystal. S2: The laser crystal converts the pump light into fundamental frequency light with a wavelength of 1064nm; S3: The fundamental frequency light enters the FP etalon, which tunes the fundamental frequency light and compresses the line width of the fundamental frequency light. S4: the second plano-concave mirror reflects the fundamental frequency light to the dichroic mirror, the dichroic mirror reflects the fundamental frequency light to the Raman conversion module, and the Raman conversion module performs a frequency doubling operation on the fundamental frequency light; S5: The frequency-doubled light enters the low-pass filter, which filters out the pump light and Stokes light in the frequency-doubled light and outputs pure frequency-doubled light.

10. The method for emitting a tunable narrow linewidth diamond Raman laser according to claim 9, characterized in that: In step S4, the Raman conversion module performs a frequency doubling operation on the fundamental frequency light, which specifically includes the following steps: S41: The fundamental frequency light enters the diamond crystal, and the diamond crystal performs Raman conversion on the fundamental frequency light, outputting Raman light with a wavelength between 1221.73nm and 1257.15nm; S42: The Raman light enters the LBO frequency doubling crystal, and the LBO frequency doubling crystal doubles the frequency of the Raman light to output a frequency doubling light with a wavelength between 610.87nm and 628.58nm.

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