A red-green-blue three-primary color large pulse energy Raman laser

Abstract

The application belongs to the field of Raman laser, and particularly relates to a red-green-blue three primary color large pulse energy Raman laser, which comprises a pumping laser, a plano-convex lens A, a Raman cell and a plano-convex lens B, the pumping laser is a Nd:YAG pulse solid laser, a mixed gas of D2 and inert gas in the Raman cell is pumped by a doubled 532nm pulse laser, three times of focusing are carried out in the Raman cell, and finally first order Stokes red laser, first order anti-Stokes blue Raman laser and green pumping laser are simultaneously output, the pulse energy reaches above 140mJ, 50mJ and 140mJ respectively, and the peak power reaches 10MW level. The application has the advantages of simple structure, fast debugging, low cost and high peak power of output laser, and provides a Raman laser for generating red-green-blue three primary color laser with high cost performance and large pulse energy.

Description

Technical Field

[0001] This invention belongs to the field of Raman lasers, specifically a high-energy Raman laser with red, green and blue primary colors. Background Technology

[0002] Lasers, due to their inherent advantages such as high coherence and monochromaticity, are widely used in numerous fields including industry, national defense, and medicine. However, existing lasers cannot meet the diverse wavelength requirements of various industries, thus necessitating the development of laser wavelength conversion. Stimulated Raman scattering of gas possesses characteristics such as a high damage threshold, large Raman frequency shift, and high conversion efficiency. Furthermore, it can achieve longer wavelength laser outputs than pump lasers using Stokes Raman lasers and shorter wavelength laser outputs than pump lasers using anti-Stokes Raman lasers. Therefore, Raman lasers are an important frequency conversion method.

[0003] Red, green, and blue are the three basic colors in nature. Any visible color can be synthesized from red, green, and blue. Red, green, and blue primary color lasers are commonly used in laser displays, scientific research (as pump sources), and medical fields. At the same time, red, green, and blue primary color lasers are also a model of multi-functional lasers, realizing the synthesis of three types of lasers and greatly reducing the cost of developing red, blue, and green lasers separately.

[0004] In summary, in order to meet the demand for red, green, and blue primary color lasers in the aforementioned fields, there is an urgent need to develop a red, green, and blue primary color Raman laser with high pulse energy, high peak power, and high cost-effectiveness. This laser source will receive increasingly widespread attention in many fields. Summary of the Invention

[0005] In order to meet the demand for red, green and blue primary color lasers in many fields, the purpose of this invention is to provide a red, green and blue primary color high pulse energy Raman laser.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention includes a pump laser and a plano-convex lens A, a Raman cell, and a plano-convex lens B arranged sequentially in the direction of the pump laser output. The Raman cell has a window A at one end near plano-convex lens A and a window B at the other end near plano-convex lens B. Concave mirrors for transmitting and focusing the laser are located at both ends of the Raman cell along its length. The Raman cell is filled with a Raman gas medium, which is a mixture of D2 and an inert gas. The pump laser emitted by the pump laser enters the Raman cell through window A at one end of the Raman cell via plano-convex lens A. The plano-convex lens A focuses the pump laser to a central point within the Raman cell space, and the laser is reflected by the concave mirrors within the Raman cell. Subsequently, the pump laser is output from window B at the other end of the Raman cell. The pump laser is refracted and transmitted multiple times within the Raman cell to extend the interaction length between the pump laser and the Raman gas medium. The transmission distance reaches three times the length of the Raman cell. The pump laser is focused three times within the Raman cell, with the three focal points located at the spatial center along the length of the Raman cell, and each focal point is non-overlapping in space. During the laser transmission process, the pump laser output from the pump laser interacts with the Raman gas medium within the Raman cell, generating a first-order Stokes red Raman laser and a first-order anti-Stokes blue Raman laser. After being collimated by the plano-convex lens B, the laser emitted from the Raman cell is finally output simultaneously as red, green, and blue primary color lasers.

[0008] Wherein: There are two concave mirrors in the Raman cell, namely concave mirror A and concave mirror B. Concave mirror B is located at one end of the Raman cell near window A, and concave mirror A is located at the other end of the Raman cell near window B. The pump laser injected from window A first irradiates concave mirror A, and is reflected by concave mirror A to concave mirror B, and then reflected by concave mirror B before being output from window B.

[0009] The concave mirrors A and B are simultaneously coated with a film system that highly reflects the pump laser wavelength, the first-order Stokes Raman laser wavelength, and the first-order anti-Stokes Raman laser wavelength while highly transmitting the second-order Stokes Raman laser wavelength. The second-order Stokes Raman laser transmitted through the concave mirrors A and B is absorbed by the inner wall of the Raman cell. The concave mirrors A and B have the same radius of curvature, which is equal to 0.43 to 0.46 times the length of the Raman cell.

[0010] The inert gas is He or Ar. The Raman cell is first filled with D2, and the pressure of D2 is adjusted within the range of 1.5 to 5 atmospheres so that the Raman laser does not output second-order Stokes Raman laser. Then He or Ar is filled in, and the pressure of He or Ar is adjusted within the range of 0.5 to 2.5 atmospheres until the output blue light pulse energy reaches its maximum.

[0011] The plano-convex lens A is coated with a film system that has high transmission of pump laser wavelength, and the focal length f of the plano-convex lens A is equal to 0.53 to 0.55 times the length of the Raman cell.

[0012] Window A is coated with a film system that has high transmission of pump laser wavelength, while window B is coated with a film system that has high transmission of pump laser wavelength, first-order Stokes Raman laser wavelength and first-order anti-Stokes Raman laser wavelength.

[0013] The plano-convex lens A is a long focal length lens with its focal point located at the 1 / 2 position in the spatial direction of the Raman cell length; the plano-convex lens B is a long focal length lens coated with a multi-wavelength high-transmittance film, which shapes the diverging laser beam into a parallel laser beam, and finally outputs parallel laser beams of the three primary colors of red, green and blue; the plano-convex lens B is also coated with a film system that has high transmittance for the pump laser wavelength, the first-order Stokes Raman laser wavelength and the first-order anti-Stokes Raman laser wavelength.

[0014] The plano-convex lens B can be replaced by a concave reflector to eliminate chromatic aberration of lasers of different wavelengths. The radius of curvature of the concave reflector is 1.2 to 1.5 times the length of the Raman cell. By changing the distance between the concave reflector replacing the plano-convex lens B and the Raman cell, the reflected beam is made as parallel as possible. The concave reflector replacing the plano-convex lens B is coated with a 0° red, green and blue three-wavelength high-reflection film.

[0015] The Raman cell adopts a Herriot-type multi-pass cell structure, the length of the Raman cell is in the range of 1.5 to 3m, and the wall thickness of the cell meets the pressure bearing conditions of the Raman gas medium.

[0016] The advantages and positive effects of this invention are as follows:

[0017] This invention is a device for laser wavelength conversion by generating Stokes and anti-Stokes Raman lasers through stimulated Raman scattering of gas. It provides a high-performance Raman laser that generates high-energy red, green and blue primary color lasers with high cost-effectiveness. This invention has a simple and compact structure, is easy to install and debug, is inexpensive, and has a high peak output laser power. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0019] Wherein: 1 is the pump laser, 2 is the plano-convex lens A, 3 is the Raman cell, 4-1 is the window A, 4-2 is the concave mirror A, 4-3 is the concave mirror B, 4-4 is the window B, and 5 is the plano-convex lens B. Detailed Implementation

[0020] The invention will now be described in further detail with reference to the accompanying drawings.

[0021] This invention relates to a Raman laser that utilizes stimulated Raman scattering (SRS) of a gas to simultaneously output multiple wavelengths of laser light in the visible light band. Through SRS, first-order Stokes and first-order anti-Stokes Raman lasers are generated within a Raman cell 3, and then collimated by a plano-convex lens B5 before being output. A key feature of this invention is the use of a Herriot-type multi-pass cell structure. To achieve efficient conversion between 459 nm blue and 633 nm red lasers, three focusing operations are performed within the Raman cell 3. By adjusting the pressure conditions of the Raman gas medium within the Raman cell 3, a first-order Stokes red Raman laser, a first-order anti-Stokes blue Raman laser, and a green pump laser are simultaneously output. When the pump laser pulse energy exceeds 400 mJ, the red, green, and blue laser pulse energies reach 140 mJ, 140 mJ, and 50 mJ or higher, respectively, with peak powers reaching the 10 MW level. The specific structure is as follows:

[0022] like Figure 1 As shown, the present invention includes a pump laser 1, a plano-convex lens A2, a Raman cell 3, and a plano-convex lens B5. The plano-convex lens A2, the Raman cell 3, and the plano-convex lens B5 are arranged sequentially in the direction in which the pump laser 1 outputs laser light. The Raman cell 3 has a window A4-1 at one end near the plano-convex lens A2 and a window B4-4 at the other end near the plano-convex lens B5. Both ends of the Raman cell 3 in the length direction are provided with concave reflectors that serve to transmit and focus the laser light. The Raman cell 3 is filled with a Raman gas medium.

[0023] Pump laser 1 is a pulsed laser. The pump laser emitted by pump laser 1 enters Raman cell 3 through window A4-1 at one end of Raman cell 3 via plano-convex lens A2. The plano-convex lens A2 focuses the pump laser to a central point within Raman cell 3. After reflection by a concave mirror within Raman cell 3, the laser is output through window B4-4 at the other end of Raman cell 3. The pump laser refracts and propagates multiple times within Raman cell 3 to extend the interaction length between the pump laser and the Raman gas medium, achieving a transmission distance three times the length of the Raman cell. The pump laser is focused three times within the Raman cell 3, with each focal point located at the spatial center along the length of the Raman cell 3, and none of the focal points coincide in space. During laser transmission, the pump laser output from the pump laser 1 interacts with the Raman gas medium within the Raman cell 3, consuming the energy of the pump laser and generating a first-order Stokes red Raman laser and a first-order anti-Stokes blue Raman laser. After being collimated by the plano-convex lens B5, the laser emitted from the Raman cell 3 ultimately outputs red, green, and blue primary color lasers simultaneously.

[0024] The plano-convex lens A2 is a long focal length lens with a focal length f equal to 0.53 to 0.55 times the length of the Raman cell 3. The plano-convex lens A2 plays the role of focusing the laser beam, with the focal point located at the spatial center of the Raman cell 3. The plano-convex lens A2 is coated with a film system that has high transmission (T > 99.5%) of the pump laser wavelength.

[0025] Raman cell 3 is a closed hollow cavity. Coated windows A4-1 and B4-4 are installed at both ends of Raman cell 3. Raman cell 3 can withstand Raman gas media up to 1 MPa. It is filled with a mixture of D2 and inert gas (volume ratio 1:1). The inert gas can be He or Ar. By changing the pressure of the gas medium inside Raman cell 3, the conversion efficiency of first-order Stokes and first-order anti-Stokes Raman lasers can be optimized. At the same time, concave mirrors A4-2 and B4-3 are installed inside Raman cell 3. The concave mirrors play the role of laser transmission and focusing, extending the interaction distance between the pump laser and the Raman gas medium, and increasing the conversion efficiency of Raman laser near the focal point.

[0026] The laser-injected window A4-1 at one end of the Raman cell 3 is coated with a film system that has high transmission (T>99.5%) of the pump laser wavelength, while the laser-out window B4-4 is coated with a film system that has high transmission (T>99.5%) of the pump laser wavelength, the first-order Stokes Raman laser wavelength, and the first-order anti-Stokes Raman laser wavelength.

[0027] Concave mirror B4-3 is located inside Raman cell 3 near window A4-1, and concave mirror A4-2 is located inside Raman cell 3 near window B4-4. Pump laser entering through window A4-1 first irradiates concave mirror A4-2, and is reflected by concave mirror A4-2 to concave mirror B4-3, and then reflected by concave mirror B4-3 before being output through window B4-4. Concave mirrors A4-2 and B4-3 are simultaneously coated with a film system that exhibits high reflectivity (R > 99.5%) for the pump laser wavelength, the first-order Stokes Raman laser wavelength, and the first-order anti-Stokes Raman laser wavelength, while simultaneously exhibiting high transmittance (T > 99.5%) for the second-order Stokes Raman laser wavelength. The second-order Stokes Raman laser light transmitted through concave mirrors A4-2 and B4-3 is absorbed by the inner wall of Raman cell 3. Furthermore, the concave mirrors A4-2 and B4-3 have the same radius of curvature, both equal to 0.43 to 0.46 times the length of Raman cell 3.

[0028] The plano-convex lens B5 is a high-transmission (T>99.5%) film system that simultaneously coats the pump laser wavelength, the first-order Stokes Raman laser wavelength, and the first-order anti-Stokes Raman laser wavelength; the plano-convex lens B5 is a long focal lens coated with multi-wavelength high-transmission film, which shapes non-parallel lasers into parallel lasers.

[0029] Example

[0030] In this embodiment, the pump source is an Nd:YAG pulsed solid-state laser, and the pump laser is a frequency-doubled 532 nm laser with a pulse width of 5–50 nanoseconds.

[0031] The Nd:YAG pulsed solid-state laser outputs a pump laser with a wavelength of 532 nm. This pump laser first passes through a plano-convex lens A2 coated with a 532 nm high-transmittance film, then enters the Raman cell 3 through a window A4-1 also coated with a 532 nm high-transmittance film. The plano-convex lens A2 acts as a focusing point, focusing the 532 nm pump laser to half the length of the Raman cell 3. It then passes through concave mirrors A4-2 and B4-3 for reflection, is transmitted through window B4-4, and collimated by the plano-convex lens B5. During its propagation within the Raman cell 3, the 532 nm pump laser interacts with the Raman gas medium, ultimately being transmitted through the plano-convex lens B5 to output a 459 nm first-order anti-Stokes Raman blue laser, a 633 nm first-order Stokes Raman red laser, and a 532 nm green residual pump laser. The pulse energies are 50 mJ, 140 mJ, and above 140 mJ, respectively, with peak powers on the order of 10 MW.

[0032] A plano-convex lens A2 is placed at the front end of the laser incident window A4-1 on the Raman cell 3, with a focal length of 1000 mm. Its focal point falls on a point in the center of the space inside the Raman cell 3. The plano-convex lens A2 is coated with a 532 nm high-transmittance film (T > 99.5%).

[0033] Raman cell 3 is made of 304 stainless steel, with a hollow chamber structure, a length of 1800 mm, an outer diameter of 100 mm, and an inner diameter of 80 mm. Windows A4-1 and B4-4 at both ends are fixed by flanges, ensuring good sealing. Concave reflectors A4-2 and B4-3 are installed inside, with the radius of curvature of the concave surfaces being -800 mm. Before the experiment, Raman cell 3 is filled with a mixture of D2 and He or a mixture of D2 and Ar (here, a mixture of D2 and He is selected) at a set pressure. The pressure of D2 is 0.15–0.5 MPa, and the pressure of He is 0.05–0.25 MPa. The addition of the inert gas He helps to adjust the dispersion and suppress the generation of second-order Stokes Raman laser with a wavelength of 780 nm.

[0034] The window A4-1 at the laser incident end of the Raman cell is coated with a 532 nm high-transmittance film (T > 99.5%), and the window B4-4 at the laser exit end is coated with 532 nm, 633 nm, and 459 nm high-transmittance films (T > 99.5%).

[0035] The surfaces of concave mirrors A4-2 and B4-3 in Raman cell 3 are coated with high reflectivity films of 532 nm, 633 nm, and 459 nm (R > 99.5%) and a high transmittance film of 780 nm (T > 99.5%), and the transmitted 780 nm laser is absorbed by the inner wall of Raman cell 3.

[0036] The surface of the plano-convex lens B5 is coated with a high-transmittance film of 532 nm, 633 nm, and 459 nm (T > 99.5%). The plano-convex lens B5 is a long focal length lens with a focal length of 1000 mm.

Claims

1. A high-energy, red-green-blue three-primary-color large-pulse Raman laser, characterized in that: The system includes a pump laser (1) and a plano-convex lens A (2), a Raman cell (3), and a plano-convex lens B (5) arranged sequentially in the direction of the output laser from the pump laser (1). The Raman cell (3) has a window A (4-1) near the plano-convex lens A (2) and a window B (4-4) near the plano-convex lens B (5). Concave mirrors for transmitting and focusing the laser are provided at both ends of the Raman cell (3) along its length. The Raman cell (3) is filled with a Raman gas medium, which is a mixture of D2 and an inert gas. The pump laser emitted by the pump laser (1) enters the Raman cell (3) through the window A (4-1) at one end of the Raman cell (3) via the plano-convex lens A (2). The plano-convex lens A (2) focuses the pump laser to a central point within the Raman cell (3). After being reflected by the concave mirror in the Raman cell (3), the pump laser is output from the window B (4-4) at the other end of the Raman cell (3). The pump laser is refracted and transmitted multiple times in the Raman cell (3) to extend the interaction length between the pump laser and the Raman gas medium. The transmission distance reaches three times the length of the Raman cell body. The pump laser is focused three times in the Raman cell (3). The three focal points are located at the spatial center position in the length direction of the Raman cell (3), and each focal point does not coincide in space. During the laser transmission process, the pump laser output by the pump laser (1) interacts with the Raman gas medium in the Raman cell (3) to generate a first-order Stokes red Raman laser and a first-order anti-Stokes blue Raman laser. The laser emitted from the Raman cell (3) is collimated by the plano-convex lens B (5) and finally outputs red, green and blue primary color lasers simultaneously.

2. The red, green, and blue three-primary-color high-pulse-energy Raman laser according to claim 1, characterized in that: The Raman cell (3) contains two concave mirrors, namely concave mirror A (4-2) and concave mirror B (4-3). Concave mirror B (4-3) is located at one end of the Raman cell (3) near window A (4-1), and concave mirror A (4-2) is located at the other end of the Raman cell (3) near window B (4-4). The pump laser injected through window A (4-2) first irradiates concave mirror A (4-2), and is reflected by concave mirror A (4-2) onto concave mirror B (4-3), and then reflected by concave mirror B (4-3) and output through window B (4-4).

3. The red, green, and blue three-primary-color high-pulse-energy Raman laser according to claim 2, characterized in that: The concave mirrors A (4-2) and B (4-3) are coated with a film system that has high reflectivity for pump laser wavelength, first-order Stokes Raman laser wavelength, and first-order anti-Stokes Raman laser wavelength, while having high transmittance for second-order Stokes Raman laser wavelength. The second-order Stokes Raman laser transmitted through the concave mirrors A (4-2) and B (4-3) is absorbed by the inner wall of the Raman cell (3). The concave mirrors A (4-2) and B (4-3) have the same radius of curvature, which is equal to 0.43 to 0.46 times the length of the Raman cell (3).

4. The red, green, and blue three-primary-color high-pulse-energy Raman laser according to claim 1, characterized in that: The inert gas is He or Ar. The Raman cell (3) is first filled with D2, and the pressure of D2 is adjusted in the range of 1.5 to 5 atmospheres so that the Raman laser does not output second-order Stokes Raman laser. Then He or Ar is filled in, and the pressure of He or Ar is adjusted in the range of 0.5 to 2.5 atmospheres until the output blue light pulse energy reaches the maximum.

5. The red, green, and blue high-pulse energy Raman laser according to claim 1, characterized in that: The plano-convex lens A (2) is coated with a film system that has high transmission of pump laser wavelength, and the focal length f of the plano-convex lens A (2) is equal to 0.53 to 0.55 times the length of the Raman cell (3).

6. The red, green, and blue three-primary-color high-pulse-energy Raman laser according to claim 1, characterized in that: Window A (4-1) is coated with a film system that has high transmission of pump laser wavelength, and window B (4-4) is coated with a film system that has high transmission of pump laser wavelength, first-order Stokes Raman laser wavelength and first-order anti-Stokes Raman laser wavelength.

7. The red, green, and blue high-pulse energy Raman laser according to claim 1, characterized in that: The plano-convex lens A (2) is a long focal length lens with its focal point located at 1 / 2 of the spatial position along the length of the Raman cell (3); the plano-convex lens B (5) is a long focal length lens coated with a multi-wavelength high-transmittance film, which shapes the divergent laser beam into a parallel laser beam and finally outputs parallel laser beams of the three primary colors of red, green and blue; the plano-convex lens B (5) is coated with a film system that has high transmittance for the pump laser wavelength, the first-order Stokes Raman laser wavelength and the first-order anti-Stokes Raman laser wavelength.

8. The red, green, and blue high-energy Raman laser according to claim 1, characterized in that: The plano-convex lens B (5) is replaced by a concave reflector to eliminate the chromatic aberration of lasers of different wavelengths. The radius of curvature of the concave reflector is 1.2 to 1.5 times the length of the Raman cell. The distance between the concave reflector replacing the plano-convex lens B (5) and the Raman cell (3) is changed to make the reflected beam as parallel as possible. The concave reflector replacing the plano-convex lens B (5) is coated with a 0° red, green and blue three-wavelength high-reflection film.

9. The red, green, and blue high-pulse energy Raman laser according to claim 1, characterized in that: The Raman cell (3) adopts a Herriot type multi-pass cell structure. The length of the Raman cell (3) is in the range of 1.5 to 3m, and the wall thickness of the cell meets the pressure bearing conditions of the Raman gas medium.

Images