A high repetition rate large energy pulse raman laser with backscattering output

Abstract

The application belongs to the field of Raman laser, and particularly relates to a high-repetition-frequency high-energy pulsed Raman laser with backward scattering output, which comprises a dichroic mirror, a Raman cell A, a 45-degree reflecting mirror, a plano-convex lens and a Raman cell B arranged in sequence along the direction of laser emission of a pumping laser; the laser passes through the dichroic mirror, the Raman cell A, the 45-degree reflecting mirror, the plano-convex lens and the Raman cell B in sequence, wherein the first-order Raman laser is generated in the Raman cell B, the forward transmission Raman laser is absorbed by the inner wall of the Raman cell B, the backward transmission Raman laser returns to the Raman cell A as seed light, and the laser entering the Raman cell A is amplified and then the backward first-order Stokes Raman light is finally emitted vertically through the dichroic mirror. The application uses the backward stimulated Raman scattering light as seed light to generate Raman laser after amplification, has low requirement on the laminar flow of Raman medium, good Raman beam quality and relatively simple structure.

Description

Technical Field

[0001] This invention belongs to the field of Raman lasers, specifically a high repetition rate, high energy pulsed Raman laser with backscattering output. Background Technology

[0002] There are many types of laser frequency conversion methods, such as frequency doubling, difference frequency conversion, sum frequency conversion, optical parametric oscillation, and stimulated Raman scattering (SRS). Among them, stimulated Raman scattering (SRS) is a commonly used laser frequency conversion method. Although gaseous Raman media have relatively low gain, they are characterized by being less prone to damage and having a large Raman frequency shift. Therefore, gaseous medium Raman frequency conversion has important application value in the field of high peak power, high pulse energy laser frequency conversion.

[0003] High-repetition-rate, high-energy pulsed lasers are widely used in scientific research, aerospace, and machining, with a very broad application prospect. "High repetition rate" is necessary to meet the requirement of high laser efficiency, while "high energy" is one of the essential conditions for generating strong-field physical phenomena. In industrial technology, material flaw detection often requires high-energy lasers to interact with electrons to generate gamma rays, and the laser pulse frequency needs to reach tens or even hundreds of hertz to meet the requirements for flaw detection efficiency. Furthermore, high repetition rate is also a guarantee of processing efficiency in industrial applications such as precision machining and impact strengthening.

[0004] In summary, to meet the demands of industries and scientific research for high-pulse-frequency, high-energy lasers that output specific wavelengths, there is an urgent need to develop a novel, high-repetition-rate, high-energy pulsed Raman laser. High-repetition-rate, high-energy pulsed Raman lasers generate a significant amount of heat, typically requiring a circulating gaseous Raman medium. However, to achieve high Raman conversion efficiency, the pressure of the gaseous Raman medium is usually several atmospheres or even higher. For high-pressure gases, laminar circulation is extremely difficult, and the design requirements for the Raman cell's surface shape are exceptionally stringent. Summary of the Invention

[0005] In response to the need for high-pulse-frequency, high-energy lasers that output specific wavelengths, the present invention aims to provide a high-repetition-rate, high-energy pulsed Raman laser with backscattering output.

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

[0007] This invention includes a pump laser, an amplification stage of a Raman laser, a 45° angle mirror, and an oscillation stage of the Raman laser. The amplification stage of the Raman laser includes a Raman cell A and a dichroic mirror located between Raman cell A and the pump laser. The oscillation stage of the Raman laser includes a plano-convex lens and a Raman cell B. Both the plano-convex lens and the 45° angle mirror are located between Raman cell A and Raman cell B. Raman cell A has a window A at one end near the dichroic mirror and a window B at the other end near the 45° angle mirror. Plane mirrors are located at both ends along the length of Raman cell A. Raman cell B has a window C at one end near the plano-convex lens. Raman cell A and Raman cell B are respectively filled with Raman gas media. The pump laser emitted by the pump laser enters Raman cell A through window A at one end of Raman cell A via the dichroic mirror. The pump laser is alternately reflected by the plane mirrors at both ends of the Raman cell A, and after being reflected back multiple times the length of the Raman cell A, it exits through window B at the other end of the Raman cell A. The pump laser then passes through the 45° angle mirror and the plano-convex lens in sequence and enters the Raman cell B through window C at one end of the Raman cell B. It is then focused to a point in space at the center of the Raman cell B along its length. The pump laser undergoes forward Raman scattering and backscattering in the Raman cell B. The backscattered Raman laser, as the seed light, returns along the original path and passes through the plano-convex lens and the 45° angle mirror in sequence before entering the Raman cell A. It is amplified in the Raman cell A and finally reflected by the dichroic mirror to output a first-order Stokes Raman laser. The forward Raman laser and the remaining pump laser in the Raman cell B are absorbed by the inner wall of the Raman cell B.

[0008] Wherein: the pump laser emitted by the pump laser does not generate Raman laser when it first enters Raman cell A. When it enters Raman cell B, it generates seed light for a backward first-order Stokes Raman laser. After returning along the original path, it is finally amplified in Raman cell A.

[0009] The Raman cell A is connected to a gas medium circulation device A for making the Raman gas medium flowable, and the Raman cell B is connected to a gas medium circulation device B for making the Raman gas medium flowable.

[0010] The Raman cell A and Raman cell B are filled with the same Raman gas medium, which is a high-purity gas of CH4 or CO2. The pressure of the Raman gas medium in Raman cell A is lower than the pressure of the Raman gas medium in Raman cell B.

[0011] The dichroic mirror is coated with a film that has high transmission at a 45° angle to the pump laser on one side, and a film that has high transmission at a 45° angle to the pump laser and high reflection at the first-order Stokes Raman laser wavelength on the other side.

[0012] The inner and outer surfaces of windows A, B, and C are simultaneously coated with films that have high transmission rates for both the pump laser wavelength and the first-order Stokes Raman laser wavelength.

[0013] The Raman cell A contains four plane mirrors: plane mirror A, plane mirror B, plane mirror C, and plane mirror D. Plane mirrors A and C are located on one side of the mounting window B. The pump laser entering through window A first irradiates plane mirror A. Plane mirrors B and D are located on one side of the mounting window A. The reflective surfaces of plane mirrors A, B, C, and D are simultaneously coated with a film system that provides high reflectivity for both the pump laser wavelength and the first-order Stokes Raman laser wavelength.

[0014] There are two 45° angle reflectors, namely 45° angle reflector A and 45° angle reflector B. 45° angle reflector A and 45° angle reflector B are arranged sequentially along the pump laser propagation direction and are perpendicular to each other. The reflective surfaces of 45° angle reflector A and 45° angle reflector B are coated with a high reflectivity film system of pump laser wavelength and first-order Stokes Raman laser wavelength.

[0015] The plano-convex lens has a double-sided coated film system with high transmission between the pump laser wavelength and the first-order Stokes Raman laser wavelength.

[0016] The first-order Stokes Raman laser reflected by the dichroic mirror is separated from the incident pump laser at a 90° angle.

[0017] The focal point of the plano-convex lens is located at 1 / 2 of the length of the inner body of the Raman cell B, and the plano-convex lens is a short focal length lens with a focal length of less than half a meter.

[0018] The relationship between the pump laser pulse width and the inner length of the Raman cell A satisfies: the speed of light × pulse width ≥ 3 times the sum of the inner length of the Raman cell A and the focal length of the plano-convex lens.

[0019] The advantages and positive effects of this invention are as follows:

[0020] This invention has relatively low requirements for laminar flow in gas Raman media, and the Raman laser beam quality is good, close to that of the pump light beam quality. At the same time, back-stimulated Raman scattering has the characteristic of compressing the laser pulse width, and finally outputs a Raman laser with high repetition rate, high energy and high peak power. In addition, the structure of this invention is relatively simple, and it is convenient and quick to install and debug. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0022] Wherein: 1 is the pump laser, 2 is the dichroic mirror, 3 is the Raman cell A, 4-1 is the window A, 4-2 is the plane mirror A, 4-3 is the plane mirror B, 4-4 is the plane mirror C, 4-5 is the plane mirror D, 4-6 is the window B, 5 is the gas medium circulation device A, 6 is the 45° angle mirror A, 7 is the 45° angle mirror B, 8 is the plano-convex lens, 9 is the Raman cell B, 10 is the window C, and 11 is the gas medium circulation device B. Detailed Implementation

[0023] The invention will now be described in further detail with reference to the accompanying drawings.

[0024] like Figure 1 As shown, the present invention includes a pump laser 1, an amplification stage of a Raman laser, a 45° angle mirror, and an oscillation stage of a Raman laser. The oscillation stage of the Raman laser generates backward stimulated Raman seed light, and the amplification stage of the Raman laser amplifies the backward stimulated Raman seed light. The amplification stage of the Raman laser includes a Raman cell A3 and a dichroic mirror 2 located between the Raman cell A3 and the pump laser 1. The oscillation stage of the Raman laser includes a plano-convex lens 8 and a Raman cell B9. The plano-convex lens 8 and the 45° angle mirror are both located between the Raman cell A3 and the Raman cell B9. A window A4-1 is provided at one end of the Raman cell A3 near the dichroic mirror 2, and a window B is provided at the other end near the 45° angle mirror. 4-6, both ends of the Raman cell A3 along its length are provided with plane mirrors; Raman cell B9 has a window C10 at one end near the plano-convex lens 8. Raman cell A3 and Raman cell B9 are respectively filled with Raman gas medium. Raman cell A3 is connected to a gas medium circulation device A5 for making the Raman gas medium flow, and Raman cell B9 is connected to a gas medium circulation device B11 for making the Raman gas medium flow. The gas medium circulation device of the present invention is prior art, including a circulation pump and a gas pipeline. The inlet and outlet of the circulation pump are respectively connected to the Raman cell through the gas pipeline. The design of the gas medium circulation device reduces the generation of thermal effects during stimulated Raman scattering.

[0025] Both Raman cells A3 and B9 must be filled with a Raman gas medium. The appropriate gas is selected based on the output Raman laser wavelength, but it is crucial that both cells are filled with the same Raman gas medium simultaneously. The Raman gas medium capable of generating stimulated Raman lasing is a high-purity gas such as CH4 or CO2 with a set pressure. The pressure of the Raman gas medium in Raman cell A3 is relatively low to ensure that no forward Raman lasing is observed when the pump laser passes through Raman cell A3 alone. Simultaneously, Raman cell B9 is filled with a higher-pressure Raman gas medium, ensuring that the intensity of the backward Raman lasing is significantly stronger than the intensity of the forward Raman lasing.

[0026] The dichroic mirror 2 of this invention has a film on one side facing the pump laser 1, which has high transmission at a 45° angle to the pump laser wavelength, and a film on the other side, which has high transmission at a 45° angle to the pump laser wavelength and high reflection at the first-order Stokes Raman laser wavelength. The first-order Stokes Raman laser reflected by the dichroic mirror 2 is separated from the incident pump laser at a 90° angle.

[0027] The present invention provides a film system with high transmission of pump laser wavelength and first-order Stokes Raman laser wavelength that is simultaneously deposited on the inner and outer surfaces of windows A4-1, B4-6 and C10.

[0028] The number of plane mirrors can be 2^n, where n is a natural number from 1 to 8. When n = 2, the total distance of the pump laser's back-transmission within the Raman cell A3 is five times the length of the Raman cell. In this invention, the Raman cell A3 contains four plane mirrors: A4-2, B4-3, C4-4, and D4-5. Plane mirrors A4-2 and C4-4 are located on one side of the mounting window B4-6. The pump laser entering through window A4-1 first irradiates plane mirror A4-2. Plane mirrors B4-3 and D4-5 are located on one side of the mounting window A4-1. The reflective surfaces of plane mirrors A4-2, B4-3, C4-4, and D4-5 are simultaneously coated with a film system that provides high reflectivity for both the pump laser wavelength and the first-order Stokes Raman laser wavelength.

[0029] The present invention comprises two 45° angle reflectors, namely 45° angle reflector A6 and 45° angle reflector B7. 45° angle reflector A6 and 45° angle reflector B7 are arranged sequentially along the pump laser propagation direction and are perpendicular to each other. The reflective surfaces of 45° angle reflector A6 and 45° angle reflector B7 are simultaneously coated with a high reflectivity film system of pump laser wavelength and first-order Stokes Raman laser wavelength.

[0030] The plano-convex lens 8 of this invention is coated with a film system on both sides that provides high transmission of the pump laser wavelength and the first-order Stokes Raman laser wavelength. The focal point of the plano-convex lens 8 is focused at 1 / 2 of the length of the inner cell of the Raman cell B9, and the plano-convex lens 8 is a short focal length lens with a focal length of less than half a meter.

[0031] The relationship between the pump laser pulse width and the inner length of the Raman cell A3 satisfies: speed of light × pulse width ≥ 3 (the sum of the inner length of the Raman cell A3 and the focal length of the plano-convex lens 8).

[0032] The Raman cell A3 of this invention has a body made of 304 stainless steel and is a sealed container capable of withstanding Raman gas media of 0.5–4 MPa. Windows A4-1 and B4-6 are installed at both ends of Raman cell A3 via bolts, flanges, O-rings, and gaskets to ensure the airtightness between the windows and the cell body, and the windows can withstand pressures of 0.5–4 MPa. Inside Raman cell A3 are four plane mirrors. The pump laser emitted by pump laser 1 does not initially produce Raman laser light when it enters Raman cell A3. The pump laser outputs from window B4-6, enters Raman cell B9, generates a first-order Stokes Raman seed light, returns along the original path, and is finally amplified within Raman cell A3.

[0033] The Raman cell B9 of this invention has a body made of 304 stainless steel and is a sealed container capable of withstanding Raman gas media of 0.5 to 4 MPa. The coated window C10 is fixed to one end of the Raman cell B9 by flanges, O-rings, gaskets, and bolts. The pump laser is focused once inside the Raman cell B9 to generate backward first-order Stokes Raman light and forward first-order Stokes Raman light. The backward first-order Stokes Raman light is emitted from the window C10, while the forward first-order Stokes Raman light and the remaining pump laser are absorbed by the inner wall of the Raman cell B9.

[0034] The working principle of this invention is as follows:

[0035] The pump laser emitted by pump laser 1 enters Raman cell A3 through window A4-1 at one end of Raman cell A3 via dichroic mirror 2. After being alternately reflected by plane mirrors at both ends of Raman cell A3, it is refracted multiple times within Raman cell A3 by the length of the cell body before exiting through window B4-6 at the other end of Raman cell A3. The exited pump laser then passes sequentially through a 45° angle mirror and a plano-convex lens 8 before entering Raman cell B9 through window C10 at one end of Raman cell B9, where it is focused. At the center point along the length of Raman cell B9, the pump laser undergoes forward and backward Raman scattering within Raman cell B9. The backward Raman laser, acting as a seed light, returns along its original path and passes sequentially through plano-convex lens 8 and a 45° angle mirror before entering Raman cell A3. It is amplified within Raman cell A3 and finally reflected by dichroic mirror 2 to output a first-order Stokes Raman laser. The forward Raman laser and the remaining pump laser within Raman cell B9 are absorbed by the inner wall of Raman cell B9.

[0036] Example 1

[0037] In this embodiment, a Quantel high repetition rate pulsed solid-state laser is used, with a pump laser output wavelength of 1064 nm, a pulse frequency ≥ 200 Hz, and a laser pulse width of 50–100 nanoseconds.

[0038] The 1064 nm pump laser emitted by the Quantel high repetition rate pulsed solid-state laser passes through dichroic mirror 2 and enters Raman cell A3 through window A4-1 at one end. The 1064 nm pump laser is alternately reflected by four plane mirrors at both ends (i.e., after entering through window A4-1, the 1064 nm pump laser is reflected sequentially by plane mirrors A4-2, B4-3, C4-4, and D4-5). After being refracted back five times the length of the Raman cell A3, it exits through window B4-6 at the other end of Raman cell A3. No Raman laser with a wavelength of 1543 nm is generated within Raman cell A3. After being reflected by 45° angle mirrors A6 and B7, the pump laser is focused by plano-convex lens 8 onto the center point of the Raman cell B9 along its length. Within Raman cell B9, the pump laser generates a backward 1543 nm first-order Stokes Raman seed beam, which returns along its original path, passing sequentially through plano-convex lens 8, 45° angle mirror B7, and 45° angle mirror A6 before entering Raman cell A3. In Raman cell A3, the beam is amplified and, through vertical reflection by dichroic mirror 2, outputs a single-pulse first-order Stokes Raman laser with an energy of ≥1 J and a wavelength of 1543 nm, a pulse frequency ≥200 Hz, and a peak power on the order of 10 MW. Simultaneously, the remaining 1064 nm pump laser and the forward 1543 nm first-order Stokes laser within Raman cell B9 are absorbed by the inner wall of Raman cell B9.

[0039] In this embodiment, the Raman cell B9 has a total length of 0.5 meters and an outer diameter of 100 millimeters. It is a tubular structure filled with high-purity (99.99%) CH4 gas at a pressure between 0.5 and 4 MPa. One end of the Raman cell B9 is fixed to the coated window C10 by bolts, flanges, gaskets, and O-rings, while the other end is a closed structure to ensure the airtightness of the Raman cell B9. Leak testing of the Raman cell B9 is required before the experiment.

[0040] The gas medium circulation device B11, as part of the Raman cell B9, ensures the circulation of the gas medium inside the Raman cell B9.

[0041] In this embodiment, the Raman cell A3 has a total length of 0.5 meters and an outer diameter of 100 millimeters. It is a tubular structure and is filled with high-purity (99.99%) CH4 gas at a pressure between 0.5 and 4 MPa. The two ends of the Raman cell A3 are fixed with bolts, flanges, gaskets, and O-rings to the coated windows A4-1 and B4-6 to ensure the airtightness of the Raman cell A3. Leak testing of the Raman cell A3 is required before the experiment. The two Raman cells, Raman cell A3 and Raman cell B9, circulate simultaneously and are filled with the same Raman gas medium (CH4 gas).

[0042] The gas medium circulation device A5, as part of the Raman cell A3, ensures the circulation of the gas medium inside the Raman cell A3.

[0043] In this embodiment, four planar mirrors are installed inside the Raman cell A3 for laser transmission. The mirror surfaces are coated with high reflectivity films of 1064 nm and 1543 nm (R > 99.5%).

[0044] In this embodiment, the windows of Raman cell A3 and Raman cell B9 are both coated with high-transmittance films of 1064 nm and 1543 nm (T > 99.5%).

[0045] In this embodiment, the side of the dichroic mirror 2 facing the pump laser 1 is coated with a 1064 nm high-transmittance film (T > 99.5%), and the other side facing the Raman cell A3 is coated with a 1064 nm high-transmittance film (T > 99.5%) and a 1543 nm high-reflectance film (R > 99.5%).

[0046] In this embodiment, the plano-convex lens 8 is coated with a high-transmittance film of 1064 nm and 1543 nm (T > 99.5%), and its focal length is 300 mm.

[0047] Example 2

[0048] Compared to Example 1, this embodiment also uses a Quantel high-repetition-rate pulsed solid-state laser, but the pump laser output wavelength is changed to 532 nm, the gaseous Raman medium remains CH4 gas, and the wavelength of the corresponding optical element coating is changed to 532 nm and / or 630 nm. All other aspects remain unchanged from Example 1. The final output is a Raman laser with a single-pulse energy of ≥1 J, a wavelength of 630 nm, a pulse frequency ≥200 Hz, and a peak power on the order of 10 MW.

[0049] Example 3

[0050] Compared to Example 1, this embodiment also uses a Quantel high-repetition-rate pulsed solid-state laser, but the pump laser output wavelength is 1064 nm. The gaseous Raman medium is changed to CO2 gas, and the corresponding wavelength of the optical element coating is changed to 1064 nm and / or 1248 nm. All other aspects remain unchanged from Example 1. The final output is a Raman laser with a single-pulse energy of over 1 J, a wavelength of 1248 nm, a pulse frequency ≥200 Hz, and a peak power on the order of 10 MW.

[0051] Example 4

[0052] Compared to Example 3, this embodiment also uses a Quantel high-repetition-rate pulsed solid-state laser, but the pump laser output wavelength is changed to 532 nm, the gaseous Raman medium remains CO2 gas, and the wavelength of the corresponding optical element coating is changed to 532 nm and / or 574 nm. All other aspects remain unchanged from Example 3. The final output is a Raman laser with a single pulse energy of ≥1 J, a wavelength of 574 nm, a pulse frequency ≥200 Hz, and a peak power on the order of 10 MW.

[0053] This invention relates to a device for laser wavelength conversion using gas-stimulated Raman spectroscopy (GSSR). It generates and amplifies a back-biased Raman seed beam, ultimately outputting a high-repetition-rate, high-energy, first-order Stokes Raman pulsed laser. A key feature of this invention is the use of a dual Raman cell structure. To mitigate thermal effects, the Raman gas medium in both cells circulates. When the pump laser passes through Raman cell A3 alone, the gas pressure in A3 is adjusted to prevent the generation of Raman laser light. When the pump laser is transmitted to Raman cell B9, the gas pressure and focusing conditions in B9 are adjusted to generate a back-biased Raman seed beam, which then returns along its original path to Raman cell A3 for amplification, ultimately outputting a high-repetition-rate, high-energy Raman laser. To ensure high-efficiency output of the back-biased Raman laser, the pump laser preferably has a narrow linewidth (<1 cm). -1 ) laser.

Claims

1. A high-repetition-rate, high-energy pulsed Raman laser with backscattered output, characterized in that: The system includes a pump laser (1), a Raman laser amplification stage, a 45° angle mirror, and a Raman laser oscillation stage. The Raman laser amplification stage includes a Raman cell A (3) and a dichroic mirror (2) located between the Raman cell A (3) and the pump laser (1). The Raman laser oscillation stage includes a plano-convex lens (8) and a Raman cell B (9). The plano-convex lens (8) and the 45° angle mirror are both located between the Raman cell A (3) and the Raman cell B (9). The Raman cell A (3) is close to the dichroic mirror. (2) has a window A (4-1) at one end and a window B (4-6) at the other end near the 45° angle mirror. Both ends of the Raman cell A (3) in the length direction are provided with plane mirrors. The Raman cell B (9) has a window C (10) at one end near the plano-convex lens (8). The Raman cell A (3) and the Raman cell B (9) are respectively filled with Raman gas medium. The pump laser emitted by the pump laser (1) passes through the dichroic mirror (2) and passes through the window A (4-1) at one end of the Raman cell A (3). 1) The pump laser is injected into Raman cell A (3), and after being alternately reflected by the plane mirrors at both ends of Raman cell A (3), it is reflected back multiple times the length of the Raman cell A (3) and then emitted from the window B (4-6) at the other end of Raman cell A (3). The emitted pump laser is then reflected sequentially by the 45° angle mirror and the plano-convex lens (8) and then emitted into Raman cell B (9) from the window C (10) at one end of Raman cell B (9), and focused onto the center of the space in the length direction of Raman cell B (9). The pump laser undergoes forward Raman scattering and back-scattering within the Raman cell B (9). The back-scattered Raman laser, acting as a seed light, returns along its original path and passes sequentially through the plano-convex lens (8) and the 45° angle mirror before entering the Raman cell A (3). It is amplified within the Raman cell A (3) and finally reflected by the dichroic mirror (2) to output a first-order Stokes Raman laser. The forward Raman laser and the remaining pump laser within the Raman cell B (9) are absorbed by the inner wall of the Raman cell B (9). The pump laser emitted by the pump laser (1) does not generate Raman laser when it first enters the Raman cell A (3). When it enters the Raman cell B (9), it generates seed light for a backpropagating first-order Stokes Raman laser. After returning along the original path, it is finally amplified in the Raman cell A (3).

2. The high repetition rate, high energy pulsed Raman laser with backscattered output according to claim 1, characterized in that: The Raman cell A (3) is connected to a gas medium circulation device A (5) for making the Raman gas medium flowable, and the Raman cell B (9) is connected to a gas medium circulation device B (11) for making the Raman gas medium flowable.

3. The high repetition rate, high energy pulsed Raman laser with backscattered output according to claim 1, characterized in that: The Raman cell A (3) and the Raman cell B (9) are filled with the same Raman gas medium, which is CH4 or CO2 high-purity gas. The pressure of the Raman gas medium in the Raman cell A (3) is lower than the pressure of the Raman gas medium in the Raman cell B (9).

4. The high repetition rate, high energy pulsed Raman laser with backscattered output according to claim 1, characterized in that: The dichroic mirror (2) has a film with high transmission at a 45° angle to the pump laser (1) on one side and a film with high transmission at a 45° angle to the pump laser and high reflection at the first Stokes Raman laser wavelength on the other side.

5. The high repetition rate, high energy pulsed Raman laser with backscattered output according to claim 1, characterized in that: The inner and outer surfaces of windows A (4-1), B (4-6), and C (10) are simultaneously coated with films that have high transmission between the pump laser wavelength and the first-order Stokes Raman laser wavelength.

6. The high repetition rate, high energy pulsed Raman laser with backscattered output according to claim 1, characterized in that: The Raman cell A (3) contains four plane mirrors, namely plane mirror A (4-2), plane mirror B (4-3), plane mirror C (4-4), and plane mirror D (4-5). Plane mirror A (4-2) and plane mirror C (4-4) are located on one side of the mounting window B (4-6). The pump laser injected through the window A (4-1) first irradiates plane mirror A (4-2). Plane mirror B (4-3) and plane mirror D (4-5) are located on one side of the mounting window A (4-1). The reflective surfaces of plane mirror A (4-2), plane mirror B (4-3), plane mirror C (4-4), and plane mirror D (4-5) are simultaneously coated with a film system that has high reflectivity for both the pump laser wavelength and the first-order Stokes Raman laser wavelength.

7. The high repetition rate, high energy pulsed Raman laser with backscattered output according to claim 1, characterized in that: There are two 45° angle reflectors, namely 45° angle reflector A (6) and 45° angle reflector B (7). The 45° angle reflector A (6) and 45° angle reflector B (7) are arranged sequentially along the pump laser propagation direction and are perpendicular to each other. The reflective surfaces of the 45° angle reflector A (6) and 45° angle reflector B (7) are coated with a film system with high reflectivity for the pump laser wavelength and the first-order Stokes Raman laser wavelength.

8. The high repetition rate, high energy pulsed Raman laser with backscattered output according to claim 1, characterized in that: The plano-convex lens (8) has a double-sided coated film system with high transmission of pump laser wavelength and first-order Stokes Raman laser wavelength.

9. The high repetition rate, high energy pulsed Raman laser with backscattered output according to claim 1, characterized in that: The first-order Stokes Raman laser reflected by the dichroic mirror (2) is separated from the incident pump laser at a 90° angle.

10. The high repetition rate, high energy pulsed Raman laser with backscattered output according to claim 1, characterized in that: The focal point of the plano-convex lens (8) is focused at 1 / 2 of the length of the Raman cell B (9), and the plano-convex lens (8) is a short focal length lens with a focal length of less than half a meter.

11. The high repetition rate, high energy pulsed Raman laser with backscattered output according to claim 1, characterized in that: The relationship between the pump laser pulse width and the inner length of the Raman cell A (3) satisfies: the speed of light × pulse width ≥ 3 times the sum of the inner length of the Raman cell A and the focal length of the plano-convex lens.

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