Miniaturized high-energy gas Raman laser device for Bessel beam pumping

Abstract

The invention provides a Bessel beam pumped miniaturized high-energy gas Raman laser device, which comprises a laser pumping module, a Bessel beam conversion and Raman frequency conversion module and a light splitting detection module which are sequentially arranged along a laser transmission direction, the laser pumping module is used for outputting pumping light and emitting the pumping light into the Bessel beam conversion and Raman frequency conversion module; the Bessel beam conversion and Raman frequency conversion module is used for generating Bessel beams and multi-wavelength laser pulses and emitting the multi-wavelength laser pulses into the light splitting detection module; the light splitting detection module is used for recording and outputting energy light. According to the invention, the utilization rate of the Raman cell length can be improved, the focal depth can be increased, the laser-induced breakdown effect can be inhibited, and the miniaturization of the gas Raman device can be effectively realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser frequency conversion, in particular, especially relates to a Bessel beam pumped miniaturized high-energy gas Raman laser device. BACKGROUND

[0002] Stimulated Raman scattering is an important wavelength conversion method, which has been widely used in medical treatment, remote sensing and mechanical processing and many other fields. When stimulated Raman scattering is used to generate high-energy laser, it has good beam quality, high conversion efficiency and excellent scaling amplification properties. However, when generating high-energy Raman light, laser-induced breakdown effect often occurs, which causes the dissipation of pump light and Raman light and significantly deteriorates the beam quality. In order to avoid laser-induced breakdown, it is necessary to reduce the waist light intensity of the laser beam and increase the focal depth.

[0003] In the design of gas Raman laser device, the main limiting factor of output laser energy is usually laser-induced breakdown. After considering both energy conversion efficiency and laser-induced breakdown threshold, the designed optical path usually uses long-focus focusing to increase the beam waist area and thus reduce the optical power density, so it is difficult to miniaturize the Raman laser device. In order to solve this problem, the patent with publication number CN117293644A uses vortex light pumping to achieve short focal length and large beam waist area without generating laser-induced breakdown, providing a laser miniaturization scheme. However, the Raman light generated by this method is also vortex light, and there is still a length in the Raman cell area that has not been utilized, which needs to be further compressed. SUMMARY

[0004] According to the above technical problems, in order to fully utilize the length of the Raman cell, the optical power density is evenly distributed in the propagation direction of the pump light, high-energy Raman laser is generated while avoiding laser-induced breakdown effect, and a Bessel beam pumped miniaturized high-energy gas Raman laser device is provided.

[0005] The technical means adopted by the present application are as follows:

[0006] A Bessel beam pumped miniaturized high-energy gas Raman laser device, comprising: a laser pumping module, a Bessel beam conversion and Raman frequency conversion module and a light splitting and detection module placed in turn along the laser transmission direction, wherein,

[0007] The laser pumping module is used to output pump light and inject it into the Bessel beam conversion and Raman frequency conversion module;

[0008] The Bessel beam conversion and Raman frequency conversion module is used to generate Bessel beam and generate multi-wavelength laser pulses, and inject them into the light splitting and detection module;

[0009] The light splitting and detection module is used to record and output energy light.

[0010] Furthermore, the laser pumping module includes a pump laser, an optical isolator, a half-wave plate, a polarization beam splitter, and a plane mirror arranged sequentially along the laser transmission direction, with a laser beam collector provided on one side of the polarization beam splitter. The pump laser is used to generate pump light; the optical isolator is used to prevent backflow Brillouin light from returning to the laser, thus preventing damage to the laser crystal; the combination of the half-wave plate and the polarization beam splitter can achieve continuous adjustment of the laser energy entering the Bessel beam conversion and Raman frequency conversion module; the plane mirror is used to change the propagation path of the pump light, causing it to enter the Bessel beam conversion and Raman frequency conversion module.

[0011] Furthermore, the Bessel beam conversion and Raman frequency conversion module includes a dichroic mirror, a Bessel beam generating element, and a Raman cell arranged sequentially along the laser transmission direction. The dichroic mirror is used to separate the back-directed Raman light from the back-directed beam. The Bessel beam generating element is used to generate a Bessel beam, and the Bessel beam is located inside the Raman cell. The Bessel beam in the Raman cell undergoes stimulated Raman scattering, generating multi-wavelength laser pulses in both the forward and backward directions. Depending on actual needs, the forward light can be directed into the beam splitting and detection module, or the back-directed light can be directed into the beam splitting and detection module via the dichroic mirror.

[0012] Furthermore, the Bessel beam conversion and Raman frequency conversion module also includes a laser beam expanding system. Along the laser transmission direction, the laser beam expanding system is disposed between the dichroic mirror and the Bessel beam generating element, and is used to adjust the diameter and divergence angle of the pump light entering the Bessel beam generating element; and converts the pump light with adjustable diameter and divergence angle into a Bessel beam or a Bessel-like beam with adjustable focal depth through the Bessel beam generating element.

[0013] Furthermore, the laser beam expander system is an optical system composed of one or more spherical lenses; by changing lenses with different focal lengths or changing the lens spacing, the diameter and divergence angle of the pump light entering the Bessel beam generating element can be adjusted.

[0014] Furthermore, the Bessel beam generating element is a conical lens or a flat conical lens; the Bessel beam generating element is placed outside or inside the Raman cell as needed. When the incident light power is limited, insufficient to damage the optical elements and unable to cause laser-induced breakdown of air, the Bessel beam generating element can be placed outside the Raman cell, inside the laser beam expanding system, or between the dichroic mirror and the laser beam expanding system to adjust the depth of focus and tilt angle of the Bessel beam.

[0015] Furthermore, the conical lens is a transparent cone with a fixed base angle.

[0016] Furthermore, the conical lens is made of fused silica and has an antireflective coating deposited on its surface according to the transmission wavelength.

[0017] Furthermore, the flat conical lens is made of liquid crystal molecular material. Depending on the required operating wavelength, the fast axis orientation of the liquid crystal molecules is distributed in different periodic gradients along the radial direction to achieve conical phase modulation.

[0018] Furthermore, the beam splitting detection unit includes a converging lens, a Perin-Broca prism, a beam splitter, a diverging lens, and an energy meter arranged sequentially along the laser transmission direction. The Perin-Broca prism is used to spatially separate the frequency components of the output pulsed laser; the beam splitter is used to separate laser pulses of specific wavelengths; and the energy meter is used to record the output light energy.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. This invention generates a conical wavefront by phase modulation of the pump light, thus transforming the pump light into a Bessel beam. A Bessel beam is a "diffraction-free beam," allowing pump lights of different radii to be focused relatively uniformly along the propagation direction. This significantly increases the depth of focus while maintaining a relatively unchanged spot shape within the depth of focus, compressing the proportion of the non-deep-focus length. This is more conducive to balancing the negative impact of laser-induced breakdown and the energy conversion efficiency requirements within a limited length, enabling the Raman cell length to be compressed to below 0.5m.

[0021] 2. This invention converts the pump light into a Bessel beam, making full use of the beam's self-healing properties and reducing obstructions at certain locations, such as plasma generated by laser-induced breakdown, which interfere with the propagation of the pump light and cause energy dissipation. This improves the stability of the Raman laser device at high pump energies and also helps to improve the beam quality of the Raman light.

[0022] 3. After generating the pump Bessel beam, this invention produces seed light through spontaneous Raman scattering within a Raman cell. The most advantageous amplification direction for the seed light is along the optical axis, rather than in the same propagation direction as the pump beam. Therefore, the Stokes beam is a solid beam close to a Gaussian beam, rather than a ring beam. This is beneficial for purifying the beam quality and can eliminate the need for a collimating lens depending on actual needs.

[0023] 4. The Raman medium used in this invention can be a gas with a strong back-stimulated Raman scattering capability, such as methane, to generate a back-stokes laser. When a dispersive element, such as a conical lens, is used as the Bessel beam generating element, the generated back-stokes light can be converted into a plane wave and output from the back because it is phase-conjugated with the pump light.

[0024] 5. This invention can make full use of the collimation of the pump light, and the angle between the pump Bessel beam and the optical axis is highly concentrated. At the same time, the forward Stokes beam is mainly emitted along the optical axis. The wave vector angle between the two is relatively concentrated, which is conducive to generating a forward anti-Stokes laser with a fixed angle with the optical axis.

[0025] 6. This invention uses a laser beam expander system to adjust the diameter and divergence angle of the Bessel beam generating element, thereby adjusting the focal length and relative power density distribution in the propagation direction of the Bessel beam, which is beneficial for adjusting the optimal parameters under different experimental conditions.

[0026] 7. The present invention has a simple principle, simple structure, good stability, and is easy to combine with other design methods. For example, the present invention can incorporate a vortex light conversion element as described in the patent with publication number CN117293644A to convert the pump light into a higher-order Bessel beam, while utilizing the long focal depth property, self-healing property of the Bessel beam, and the increased beam waist area property of the vortex light, etc.

[0027] Based on the above reasons, this invention can be widely applied in fields such as laser frequency conversion. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of a miniaturized high-energy gas Raman laser device pumped by a Bessel beam, as described in this invention.

[0030] Figure 2 This is a schematic diagram of the cone lens in the present invention, wherein (a) is a perspective view and (b) is a front view.

[0031] Figure 3 This is a schematic diagram of the flat conical lens and its modulated phase in this invention, wherein (a) is a three-dimensional view of the flat conical lens and (b) is a front view of the modulated phase of the flat conical lens.

[0032] Figure 4 This is a schematic diagram illustrating the self-healing properties of the Bessel beam in this invention.

[0033] In the diagram: 1. Pump laser; 102. Optical isolator; 103. Half-wave plate; 104. Polarization beam splitter; 105. Laser beam collector; 106. Plane mirror; 201. Dichroic mirror; 202. Laser beam expander; 203. Bessel beam generator; 204. Raman cell; 301. Converging lens; 302. Perlin-Blocard prism; 303. Beam splitter; 304. Diverging lens; 305. Energy meter. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0038] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0039] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0040] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0041] This invention provides a miniaturized high-energy gas Raman laser device pumped by a Bessel beam, comprising a laser pumping module 1, a Bessel beam conversion and Raman frequency conversion module 2, and a beam splitting and detection module 3, arranged sequentially along the laser transmission direction. The laser pumping module 1 outputs pump light into the Bessel beam conversion and Raman frequency conversion module 2, which generates a Bessel beam and multi-wavelength laser pulses, which are then transmitted into the beam splitting and detection module 3. The beam splitting and detection module 3 records and outputs the energy light. This invention improves the utilization rate of the Raman cell length, increases the depth of focus, suppresses laser-induced breakdown, and effectively achieves miniaturization of the gas Raman device.

[0042] In a preferred embodiment, the laser pumping module 1 includes a pump laser 101, an optical isolator 102, a half-wave plate 103, a polarization beam splitter 104, and a plane mirror 106 arranged sequentially along the laser transmission direction, with a laser beam collector 105 provided on one side of the polarization beam splitter 104. The pump laser 101 generates pump light; the optical isolator 102 prevents backward Brillouin light from returning to the laser, thus preventing damage to the laser crystal; the combination of the half-wave plate 103 and the polarization beam splitter 104 enables continuous adjustment of the laser energy entering the Bessel beam conversion and Raman conversion module 2; and the plane mirror 106 changes the propagation path of the pump light, directing it into the Bessel beam conversion and Raman conversion module 2.

[0043] In a preferred embodiment, the Bessel beam conversion and Raman frequency conversion module 2 includes a dichroic mirror 201, a laser beam expander system 202, a Bessel beam generating element 203, and a Raman cell 204 arranged sequentially along the laser transmission direction. The dichroic mirror 201 is used to separate the back-directed Raman light from the back-directed beam. The laser beam expander system 202 is used to adjust the diameter and divergence angle of the pump light entering the Bessel beam generating element 203. The Bessel beam generating element 203 is used to convert the pump light with adjustable diameter and divergence angle into a Bessel beam or a Bessel-like beam with adjustable focal depth, and the Bessel beam is located inside the Raman cell 204. The Bessel beam in the Raman cell 204 undergoes stimulated Raman scattering to generate multi-wavelength laser pulses in the forward and backward directions, respectively. Depending on actual needs, the forward light can be injected into the beam splitting and detection module 3, or the back-directed light can be injected into the beam splitting and detection module 3 via the dichroic mirror 201.

[0044] In a preferred embodiment, the laser beam expander system 202 is an optical system composed of one or more spherical lenses. By replacing lenses with different focal lengths or changing the lens spacing, the diameter and divergence angle of the pump light incident on the Bessel beam generating element 203 can be adjusted.

[0045] In a preferred embodiment, the Bessel beam generating element 203 is a conical lens 2-1 or a flat conical lens 2-2; depending on actual needs, it can be placed outside or inside the Raman cell 204. When the incident light power is limited and insufficient to damage the optical elements and cannot cause laser-induced breakdown of air, the Bessel beam generating element 203 can be placed outside the Raman cell 204 and inside the laser beam expanding system 202, or placed between the dichroic mirror 201 and the laser beam expanding system 202, to adjust the depth of focus and tilt angle of the Bessel beam.

[0046] In a preferred embodiment, the conical lens 2-1 is a transparent cone with a fixed base angle; its material can be fused silica, and an anti-reflective coating is deposited on its surface according to the transmission wavelength.

[0047] In a preferred embodiment, the flat conical lens 2-2 is made of liquid crystal molecular material. Depending on the required operating wavelength, the fast axis orientation of the liquid crystal molecules exhibits a different periodic gradient distribution along the radial direction to achieve conical phase modulation.

[0048] In a preferred embodiment, the beam-splitting detection unit 3 includes a converging lens 301, a Perin-Broca prism 302, a beam-splitting aperture 303, a diverging lens 304, and an energy meter 305 arranged sequentially along the laser transmission direction. The Perin-Broca prism 302 is used to spatially separate the frequency components of the output pulsed laser; the beam-splitting aperture 303 is used to separate laser pulses of specific wavelengths; and the energy meter 305 is used to record the output light energy.

[0049] Example 1

[0050] The pump source is a Nimma-600 Nd:YAG Q-switched pulsed laser with an output spot diameter of 8 mm, a wavelength of 1064 nm, a maximum output energy of 650 mJ, and a pulse width of 10 ns. The laser is horizontally linearly polarized. Without a laser beam expander, at a repetition frequency of 1 Hz, the pump light sequentially passes through an optical isolator, a half-wave plate, a polarizing beam splitter, a plane mirror, and a dichroic mirror before entering the Raman cell. At a distance of 40 cm from the exit, it passes through a 2° conical lens (Asphericon XFL25-020-U, anti-reflection for 1064 nm and 1543 nm) to form a Bessel beam. By adjusting the half-wave plate angle, the maximum total energy of the emitted pump light is approximately 400 mJ. Neither the entrance nor exit window of the Raman cell is coated (transmittance is 93.5%), and the interior is filled with 3.5 MPa high-purity methane gas. Within the focal depth of the Bessel beam, forward-directed laser light, including a 551nm third-order anti-Stokes beam, a 656nm second-order anti-Stokes beam, an 812nm first-order anti-Stokes beam, a 1064nm residual pump beam, and a 1543nm first-order Stokes beam, is generated by stimulated Raman scattering and exits through the Raman cell exit window. Backward-directed laser light, including a 1064nm back-directed stimulated Brillouin scattering beam and a 1543nm stimulated Raman scattering first-order Stokes beam, is generated and exited after beam splitting by a dichroic mirror. Selecting either the forward or backward beam, the laser pulses are separated at the focal plane using a beam splitter via a converging lens and a Perin-Bloka prism. By moving the beam splitter left or right in a direction perpendicular to the optical path, a 1543nm laser output can be achieved. The output laser energy is recorded by an energy meter (Gentec-EO QE50LP-H-MB-D0) after passing through a diverging lens.

[0051] Example 2

[0052] The pump source is a Nimma-600 Nd:YAG Q-switched pulsed laser with an output spot diameter of 8 mm, a wavelength of 1064 nm, a maximum output energy of 650 mJ, and a pulse width of 10 ns. The laser is horizontally linearly polarized. The pump light passes sequentially through an optical isolator, a half-wave plate, a polarizing beam splitter, a plane mirror, and a dichroic mirror. After passing through a laser beam expander, it becomes an 8 mm diameter beam with a divergence angle of approximately 0.5°. This beam is then incident on a Raman cell and, at a distance of 50 cm from the exit, passes through a 2° conical lens (Asphericon XFL25-020-U, anti-reflective for 1064 nm) to form a Bessel beam. The total energy of the emitted pump light is controlled by adjusting the angle of the half-wave plate. Neither the entrance nor exit window of the Raman cell is coated (transmittance is 93.5%), and the interior is filled with 1 MPa of high-purity hydrogen gas. Within the focal depth range of the Bessel beam, the following light beams, generated by stimulated Raman scattering, are emitted from the Raman cell exit window: a 1064nm residual pump beam, a 1134nm first-order rotating Stokes beam, a 1907nm first-order vibrating Stokes beam (Q-branch), and a 2132nm Stokes beam (S-branch). After passing through a converging lens and a Perin Broca prism, a beam splitter at the focal plane separates the laser pulses into specific wavelengths. The output laser light, after passing through a diverging lens, is then recorded by an energy meter (Gentec-EO QE50LP-H-MB-D0).

[0053] Example 3

[0054] The pump source is an Nd:YAG laser (Quantel Brilliant Class-4) with an output spot diameter of 6 mm and a wavelength of 1064 nm. Utilizing its frequency-doubled 532 nm laser, the maximum output energy is 360 mJ with a pulse width of 6 ns. The laser is vertically linearly polarized. Without a laser beam expander, the pump light sequentially passes through an optical isolator, a half-wave plate, a polarizing beam splitter, a plane mirror, and a dichroic mirror. After passing through a Φ=3 mm aperture to capture the central pump light, it enters the Raman cell. At a distance of 50 cm from the exit, it passes through a flat conical lens (LBTEK PBA25-532-23) with a deflection angle of 2.3° to form a Bessel beam. The total energy of the emitted pump light is controlled by adjusting the angle of the half-wave plate. The Raman cell entrance window is coated with a 532 nm high-transmittance film (transmittance greater than 96.5%), and the exit window is a calcium fluoride window with a transmittance greater than 97% for the visible light band. The Raman cell is filled with 1 MPa of ethane gas. Within the focal depth of the Bessel beam, forward-directed stokes light (460 nm first-order anti-Stokes light, 515 nm residual pump light, 631 nm first-order Stokes light, and 776 nm second-order Stokes light) produced by stimulated Raman scattering exits from the Raman cell exit window. Backward-directed stokes light (532 nm back-directed stimulated Brillouin scattering and 631 nm first-order Stokes light) is generated and separated by a dichroic mirror before exiting. Either the forward or backward beam is selected, and after passing through a converging lens and a Perin-Bloka prism, a beam splitter is used at the focal plane to separate laser pulses of specific wavelengths. The output laser light, after passing through a diverging lens, is recorded by an energy meter (Gentec-EOQE50LP-H-MB-D0).

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A miniaturized high-energy gas Raman laser device pumped by a Bessel beam, characterized in that, The application relates to a laser energy recording and output device. The device comprises a laser pumping module (1), a Bessel beam conversion and Raman frequency conversion module (2) and a light splitting detection module (3) arranged in sequence along a laser transmission direction, wherein the laser pumping module (1) is used for outputting pumping light and injecting the pumping light into the Bessel beam conversion and Raman frequency conversion module (2); the Bessel beam conversion and Raman frequency conversion module (2) is used for generating a Bessel beam and generating multi-wavelength laser pulses and injecting the multi-wavelength laser pulses into the light splitting detection module (3); and the light splitting detection module (3) is used for recording and outputting energy light. The laser pumping module (1) comprises a pumping laser (101), an optical isolator (102), a half-wave plate (103), a polarization splitting device (104) and a plane mirror (106) arranged in sequence along the laser transmission direction, and the polarization splitting device (104) is provided with a laser beam flow collector (105) on one side; the pumping laser (101) is used for generating pumping light; the optical isolator (102) is used for preventing backward Brillouin light from returning into the laser, so as to prevent the laser crystal from being damaged; the combination of the half-wave plate (103) and the polarization splitting device (104) can realize continuous adjustment of laser energy entering the Bessel beam conversion and Raman frequency conversion module (2); and the plane mirror (106) is used for changing the propagation route of the pumping light, so that the pumping light is injected into the Bessel beam conversion and Raman frequency conversion module (2). The Bessel beam conversion and Raman frequency conversion module (2) comprises a dichroic mirror (201), a Bessel beam generating element (203) and a Raman cell (204) arranged in sequence along the laser transmission direction, wherein the dichroic mirror (201) is used for separating backward Raman light from backward light beams; the Bessel beam generating element (203) is used for generating a Bessel beam, and the Bessel beam is located inside the Raman cell (204); and the Bessel beam in the Raman cell (204) undergoes a stimulated Raman scattering process, and multi-wavelength laser pulse outputs are generated in the forward direction and the backward direction respectively, and according to actual needs, the forward light is injected into the light splitting detection module (3) or the backward light is injected into the light splitting detection module (3) through the dichroic mirror (201). The Bessel beam conversion and Raman frequency conversion module (2) further comprises a laser beam expanding system (202) arranged between the dichroic mirror (201) and the Bessel beam generating element (203) along the laser transmission direction, which is used for adjusting the diameter and divergence angle of the pumping light injected into the Bessel beam generating element (203); and the pumping light with adjustable diameter and divergence angle is converted into a Bessel beam or a Bessel-like beam with adjustable focal depth through the Bessel beam generating element (203).

2. The Bessel beam pumped compact high-energy gas Raman laser device according to claim 1, characterized in that, The laser beam expanding system (202) is an optical system composed of one or several spherical lenses; the diameter and divergence angle of the pumping light injected into the Bessel beam generating element (203) are adjusted by replacing lenses with different focal lengths or changing the distance between the lenses.

3. The Bessel beam pumped compact high-energy gas Raman laser device according to claim 1, characterized in that, ​ 4. The Bessel beam pumped compact high-energy gas Raman laser device according to claim 3, characterized in that, ​ 5. The Bessel beam pumped compact high-energy gas Raman laser device according to claim 4, characterized in that, ​ 6. The Bessel beam pumped compact high-energy gas Raman laser device of claim 4, wherein, The Bessel beam generating element (203) adopts a conical lens (2-1) or a flat conical lens (2-2); the Bessel beam generating element (203) is placed outside or inside the Raman cell (204) according to actual needs; when the incident light power is limited, insufficient to damage the optical element and cannot cause laser-induced breakdown of air, the Bessel beam generating element (203) can be placed inside the laser beam expanding system (202) or between the dichroic mirror (201) and the laser beam expanding system (202) outside the Raman cell (204) to adjust the focal depth and tilt angle of the Bessel beam.

7. The Bessel beam pumped compact high-energy gas Raman laser device according to claim 6, characterized in that, The conical lens (2-1) is a transparent circular cone with a fixed base angle.

8. The Bessel beam pumped compact high-energy gas Raman laser device according to claim 7, characterized in that, The material of the conical lens (2-1) is fused quartz, and an antireflection film is coated on the surface according to the transmission wavelength.

9. The Bessel beam pumped compact high-energy gas Raman laser device of claim 6, wherein, The flat conical lens (2-2) is made of liquid crystal molecular material, and the fast axis of the liquid crystal molecules is distributed in different periods along the radial direction to realize the conical phase modulation.

10. The Bessel beam pumped compact high-energy gas Raman laser device of claim 1, wherein, The light splitting detection unit (3) comprises a converging lens (301), a Pellin-Broca prism (302), a light splitting diaphragm (303), a diverging lens (304) and an energy meter (305) arranged in sequence along the laser transmission direction, wherein the Pellin-Broca prism (302) is used to realize the spatial separation of each frequency component of the output pulsed laser; the light splitting diaphragm (303) is used to separate out laser pulses of a specific wavelength; and the energy meter (305) is used to record the output light energy.

Images