Miniaturized high pulse energy raman laser under conditions of optical vortex pumping

Abstract

This invention provides a miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions, relating to the field of Raman laser technology, and employing n 2 A square array of vortex phase plates serves as the optical element for generating vortex-pumped lasers. By adjusting parameters such as the topological charge of the array of vortex phase plates and the focal length of the array of short-focal-length lenses, the laser power density in the focal region is reduced. The focal region has n 2 A square array is arranged with ring-shaped light intensity distribution units, ensuring that the laser power density of each unit in the focal region is greater than the Raman laser generation threshold and less than the laser-induced breakdown threshold. Therefore, the total Raman laser energy is n times the Raman laser energy generated by each unit. 2 This technology ultimately enabled the output of high-energy, high-beam-quality Raman lasers, with Raman laser pulse energies reaching hundreds of millijoules or even joules.

Description

Technical Field

[0001] This invention relates to the technical field of Raman lasers, and more particularly to a miniaturized high-pulse-energy Raman laser under vortex-pumped conditions. Background Technology

[0002] There are various laser frequency conversion methods, mainly including frequency doubling technology (KTP, LBO, BBO, etc. crystal frequency conversion), sum-frequency and difference-frequency technology, optical parametric oscillation technology (LiNbO3, KTP, LBO, etc. crystal frequency conversion), and stimulated Raman scattering (SRS). Among them, gas stimulated Raman scattering, as an important laser frequency conversion method, has many significant advantages and is widely used in industry, scientific research, and national defense. First, gas stimulated Raman scattering has the characteristic of rich laser output wavelengths, which can utilize the different Raman gas media and stimulated Raman scattering processes. The process generates Stokes and anti-Stokes lasers, enabling a wide range of laser output across different wavelengths, from ultraviolet, visible, near-infrared to mid-infrared. Secondly, the gas possesses characteristics such as good optical homogeneity, weak intermolecular forces, and strong heat dissipation, allowing it to withstand high-power lasers, resist optical damage, and recover rapidly. This enables high-power frequency-converted laser output and withstands stimulated Raman scattering processes with high repetition rates. Finally, the gas's homogeneity ensures good beam directionality, a small divergence angle, and high coherence, guaranteeing the generation of high-beam-quality Raman lasers.

[0003] Currently, free-space gas Raman lasers are developing towards shorter pulse widths, higher peak power, higher beam quality, and larger pulse energies, with peak output power reaching hundreds of megawatts and single-pulse energy in the hundreds of joules range. However, free-space gas Raman lasers also face challenges such as large gain medium container volume (Raman cell ~2m or even longer) and difficulties in system integration, which restrict their further development and application. Therefore, developing small-sized, high-power gas Raman lasers is crucial for promoting the application of miniaturized, intelligent, and integrated laser sources. Summary of the Invention

[0004] Based on the application requirements mentioned in the background section, this invention provides a miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions. This invention focuses on miniaturization, high pulse energy, and high beam quality of Raman lasers, developing a novel Raman laser with high pulse energy and good beam quality, specifically a miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions; this invention uses n 2 A square array of vortex phase plates (lithographically formed as a single unit) serves as the optical element for generating vortex-pumped lasers (n = 1, 2, 3...). By adjusting parameters such as the topological charge of the array of vortex phase plates and the focal length of the array of short-focal-length lenses, the laser power density in the focal region is reduced. The focal region has n...2 A square array of ring-shaped intensity distribution units (n = 1, 2, 3...) is arranged to ensure that the laser power density of each unit in the focal region is greater than the Raman laser generation threshold and less than the laser-induced breakdown threshold. Therefore, the total Raman laser energy is n times the Raman laser energy generated by each unit. 2 By multiplying the energy by n (n = 1, 2, 3...), a high-energy Raman laser output was finally achieved, with Raman laser pulse energy reaching the hundreds of millijoules. Because this invention uses a gas with a large back-scattering Raman gain coefficient as the Raman medium, the back-scattered stimulated Raman scattering process has a phase compensation effect, thus obtaining a high-beam-quality Raman laser. In addition, the Raman cell size in the Raman laser is relatively short (10-25 cm), and the Raman laser device is simple and easy to adjust, while also possessing the characteristics of miniaturization, integration, and lightweight.

[0005] The technical means employed in this invention are as follows:

[0006] A miniaturized high-pulse-energy Raman laser under vortex-pumped conditions includes: a pump laser, a Perinbroka prism, a half-wave plate I, a 56° angle polarizing beam splitter, a beam collector I, a half-wave plate II, a KTP crystal, a 45° angle dichroic mirror I, a beam collector II, a square array of vortex phase plates, a square array of focusing lenses, a Raman cell, and a beam collector III.

[0007] The Raman cell includes window I and window II; the surfaces of both window I and window II are coated with a high-transmission film system for the pump laser wavelength and the first-order Stokes Raman laser wavelength.

[0008] The pump laser outputs a square flat-top Gaussian laser. Along the emission direction of the fundamental frequency laser, the Perinbroka prism, the half-wave plate I, the 56° angle polarizing beam splitter, the half-wave plate II, the KTP crystal, the 45° angle dichroic mirror I, the 45° angle dichroic mirror II, the square array vortex phase plate, the square array focusing lens, the Raman cell, and the beam collector III are arranged in sequence.

[0009] After the fundamental frequency laser is output from the pump laser, it first passes through the Perinbroka prism, which deflects the propagation direction of the fundamental frequency laser by 90°. The deflected laser is then perpendicularly incident on half-wave plate I and sequentially transmitted along the optical axis through a 56° polarizing beam splitter half-wave plate II and a KTP crystal. The laser reflected from the 56° polarizing beam splitter is collected by beam collector I. A 45° dichroic mirror I separates the frequency-doubled light from the remaining fundamental frequency light from the KTP crystal. The fundamental frequency light is transmitted through the 45° dichroic mirror I and collected by beam collector II. The reflected frequency-doubled light is deflected 90° and then sequentially transmitted through the 45° dichroic mirror II, a square array of vortex phase plates, and a square array of focusing lenses. The frequency-doubled light, as the pump laser, is focused by the square array of focusing lenses onto the center of the Raman cell. A n-wave pattern appears in the focal region at the center of the Raman cell. 2 A square array of circular focal points, n = 1, 2, 3..., generates forward stimulated Raman lasers and backward stimulated Raman lasers within a Raman cell. A beam collector III collects the forward Raman laser and the remaining pump laser, while the backward first-order Stokes Raman laser is transmitted through a square array focusing lens and a square array vortex phase plate, and is finally reflected and refracted 90° by a 45° dichroic mirror II before being output. The 45° dichroic mirror II serves to separate the pump laser from the backward Raman laser.

[0010] Furthermore, both the half-wave plate I and the 56° angle polarization beam splitter of the optical element are coated with a film system that has high transmission of the fundamental frequency laser wavelength.

[0011] Furthermore, the half-wave plate II is used to adjust the polarization direction of the fundamental frequency laser, and the surface of the half-wave plate II is coated with a film system that has high transmission of the fundamental frequency laser wavelength; the surface of the KTP crystal is coated with a film system that has high transmission of both the fundamental frequency laser wavelength and the frequency-doubled laser wavelength.

[0012] Furthermore, the 45° angle dichroic mirror I separates the fundamental frequency laser and the frequency-doubled laser, and the incident angle of the laser is 45°; the surface of the 45° angle dichroic mirror I is coated with a film system that has high transmission of the fundamental frequency laser wavelength and high reflection of the frequency-doubled laser wavelength.

[0013] Furthermore, the 45° angle dichroic mirror II separates the frequency-doubled laser from the backscattered Raman laser, and the incident angle of the laser is 45°; the surface of the 45° angle dichroic mirror II is coated with a film system that has high transmission of pump laser wavelength and high reflection of backscattered first-order Stokes Raman laser wavelength.

[0014] Furthermore, the square array vortex phase plate is a single optical element made of fused silica and fabricated by photolithography; the square array vortex phase plate comprises n 2 A square array of vortex phase plate elements, n = 1, 2, 3...;

[0015] The topological charge l of each vortex phase plate unit remains consistent and is adjustable between l = 1 and l = 10. Furthermore, the surface of the square array vortex phase plate is coated with a film system that has high transmission for both the pump laser wavelength and the backward first-order Stokes Raman laser wavelength.

[0016] Furthermore, the square array focusing lens is a single optical element made of fused silica and fabricated by photolithography; the square array focusing lens comprises n 2 A square array of focusing lens units, n = 1, 2, 3..., each with a consistent focal length between 60 and 130 mm. The center of the lens is collimated with the singularity of the phase plate. The surface of the square array focusing lens is coated with a film that provides high transmission for both the pump laser wavelength and the back-propagating first-order Stokes Raman laser wavelength.

[0017] Furthermore, a pressure regulating valve and a pressure gauge are provided on the outside of the Raman cell substrate; wherein the pressure regulating valve is used for the filling and releasing of Raman gas, and the pressure gauge is used to monitor the gas pressure inside the Raman cell and whether there is leakage.

[0018] The Raman cell is filled with a Raman gas with a high backward Raman gain coefficient; the purity of the Raman gas is 99.99%; the gas pressure in the Raman cell is adjustable, and the gas pressure is between 0.5 and 4 MPa.

[0019] Furthermore, the backscattered Raman laser generated in the Raman cell returns along its original path, passing sequentially through a square array focusing lens and a square array vortex phase plate. The square array focusing lens is used for collimation of the backscattered Raman laser, and the square array vortex phase plate approximately shapes the vortex beam into a quasi-flat-top Gaussian beam. Since the backscattered Raman scattering process has a certain compensating effect on the phase change, the phase distribution of the beam is more uniform. Therefore, after collimation by the focusing lens and shaping by the vortex phase plate, a Raman laser with better beam quality is obtained.

[0020] Furthermore, by optimizing parameters such as the pump laser energy, the topological charge of the vortex phase plate in the square array, the length of the Raman cell, the focal length of the focusing lens in the square array, and the pressure of the Raman gas, the maximum energy of the back-curved Raman laser is obtained. The laser power density in the focal region is greater than the threshold for back-curved Raman laser generation but less than the threshold for laser-induced breakdown, and the output energy of the back-curved Raman laser reaches the level of hundreds of millijoules. The total output energy is approximately equal to n times the Raman laser energy generated by each array unit. 2 Times, n = 1, 2, 3...

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1) The Raman cell in the Raman laser of this invention is relatively short (10-25 cm), and it uses single-focusing, back-stimulated Raman scattering to output Raman laser light. Therefore, the entire device is small in size, has a simple optical path, and is easy and quick to assemble and adjust; 2) By using back-stimulated Raman scattering to generate Raman laser light, and because the back-stimulated Raman scattering process has a phase compensation effect, a high beam quality Raman laser can be obtained after focusing lens and vortex phase plate shaping; 3) By optimizing the pump laser energy, the topological charge of the square array vortex phase plate, and the length of the Raman cell, The maximum energy of the back-curved Raman laser is obtained by adjusting parameters such as the focal length of the focusing lens of the square array and the pressure of the Raman gas. The laser power density of the annular spot in the focal region must be greater than the back-curved Raman laser generation threshold and less than the laser-induced breakdown threshold. Under the conditions of a short Raman cell (10–25 cm) and a short focal lens (60–130 mm), the occurrence of laser-induced breakdown is avoided, while ensuring a large laser power density in the focal region, thereby obtaining a larger Raman laser output energy. The total output energy is approximately equal to n times the Raman laser energy generated by each array unit. 2 The Raman laser output energy reaches hundreds of millijoules (n = 1, 2, 3...). Attached Figure Description

[0023] 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.

[0024] Figure 1 This is a schematic diagram of the optical path of the present invention.

[0025] In the diagram: 1. Pump laser; 2. Perinbroka prism; 3-1. Half-wave plate I; 4. 56° polarizing beam splitter; 5-1. Beam collector I; 3-2. Half-wave plate II; 6. KTP crystal; 7-1. 45° dichroic mirror I; 5-2. Beam collector II; 7-2. 45° dichroic mirror II; 8. Square array vortex phase plate; 9. Square array focusing lens; 10. Raman cell; 5-3. Beam collector III; 11-1. Window I; 11-2. Window II. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] like Figure 1 As shown, the present invention provides a miniaturized high-pulse-energy Raman laser under vortex-pumped conditions, comprising: a pump laser 1, a Perinbroka prism 2, a half-wave plate 3-1, a 56° polarizing beam splitter 4, a beam collector I5-1, a half-wave plate II3-2, a KTP crystal 6, a 45° dichroic mirror I7-1, a beam collector II5-2, a square array vortex phase plate 8, a square array focusing lens 9, a Raman cell 10, and a beam collector III5-3; wherein the Raman cell 10 comprises: window I11-1 and window II11-2.

[0029] The fundamental frequency laser generated by pump laser 1 passes sequentially through a Perinbroka prism 2, a half-wave plate I3-1, a 56° polarizing beam splitter 4, a half-wave plate II3-2, a KTP crystal 6, a 45° dichroic mirror I7-1, a 45° dichroic mirror II7-2, a square array vortex phase plate 8, a square array focusing lens 9, and a Raman cell 10. At the entrance of the Raman cell 10, the frequency-doubled laser, after being frequency-doubled by the KTP crystal 6, is first shaped into n by the square array vortex phase plate 8. 2 A square array of vortex light units n = 1, 2, 3... is arranged. The square array focusing lens 9 focuses the vortex light onto the center of the Raman cell 10, forming a focal region n. 2A square array of ring-shaped light spots (n = 1, 2, 3...) generates a backward first-order Stokes Raman laser, a forward Raman laser, and a residual pump laser. The forward Raman laser and the residual pump laser are absorbed by the beam collector III5-3, while the backward Raman laser is shaped by the square array focusing lens 9 and the square array vortex phase plate 8 before being reflected by the 45° dichroic mirror II7-2. The Raman laser energy reaches the level of hundreds of millijoules. Because the backward stimulated Raman scattering process has a phase compensation effect, a Raman laser with good beam quality can be obtained.

[0030] The half-wave plate I3-1 and the 56° angle polarization beam splitter 4 need to be used together to adjust the output energy of the fundamental frequency laser, and both optical elements need to be coated with a high-transmittance film for the fundamental frequency laser.

[0031] The optical element half-wave plate II3-2 and KTP crystal 6 need to be used in combination. The half-wave plate II3-2 is used to adjust the polarization direction of the fundamental frequency laser, so that the second harmonic efficiency of KTP crystal 6 can reach more than 50%. The surface of half-wave plate II3-2 is coated with a high-transmittance film for the fundamental frequency laser, and the surface of KTP crystal 6 is coated with high-transmittance films for both the fundamental frequency laser and the second harmonic laser.

[0032] The 45° angle dichroic mirror I7-1 can separate the fundamental frequency laser and the frequency-doubled laser, and the incident angle of the laser is 45°. The surface of the 45° angle dichroic mirror I7-1 is coated with a high-transmittance film for the fundamental frequency laser and a high-reflectance film for the frequency-doubled laser.

[0033] The 45° angle dichroic mirror II7-2 separates the frequency-doubled pump laser from the back-curved Raman laser, with the laser incident at an angle of 45°. The surface of the 45° angle dichroic mirror II7-2 is coated with a high-transmittance film for the frequency-doubled laser and a high-reflectance film for the back-curved first-order Stokes Raman laser.

[0034] The square array vortex phase plate 8 and the square array focusing lens 9 are coated with pump laser and first-order Stokes Raman laser high-transmittance film. The focal length of the square array focusing lens 9 is between 60 and 130 mm, and the focal point is located at the center of the internal space of the Raman cell 10.

[0035] The Raman cell 10 is a closed container with a 50mm diameter window at each end, designated as window I11-1 and window II11-2. The total length of the Raman cell 10 is between 10 and 25cm. It is filled with a Raman gas with a high backscattered Raman gain coefficient, such as CH4 or H2, with a purity of 99.99%. The gas pressure inside the Raman cell 10 is adjustable, ensuring its airtightness and preventing leaks of flammable Raman gas. Before the Raman test, the Raman cell 10 needs to be leak-tested, and the air inside the Raman cell 10 needs to be replaced with Raman gas to ensure the purity of the Raman gas and prevent any potential hazards.

[0036] The windows at both ends of the Raman cell 10 are made of fused silica. The surfaces of windows I11-1 and II11-2 are coated with high-transmittance films of the pump laser wavelength and the first-order Stokes Raman laser wavelength.

[0037] The maximum backscattered Raman laser energy is obtained by optimizing parameters such as the energy of the pump laser frequency doubling laser, the topological charge of the square array vortex phase plate 8, the length of the Raman cell 10, the focal length of the square array focusing lens 9, and the pressure of the Raman gas.

[0038] Example 1

[0039] In this embodiment, an Nd:YAG pulsed solid-liquid laser is used. The output laser of the pump laser has a wavelength of 1064nm, a 10*10mm square spot, a flat-top Gaussian intensity distribution, and a pulse width of 20-40ns.

[0040] The Nd:YAG pulsed solid-liquid laser is arranged along the emission direction of the fundamental frequency laser as follows: Perinbrocca prism 2, half-wave plate I3-1, 56° angle polarizing beam splitter 4, half-wave plate II3-2, KTP crystal 6, 45° angle dichroic mirror I7-1, 45° angle dichroic mirror II7-2, square array vortex phase plate 8, square array focusing lens 9, Raman cell 10, and beam collector III5-3.

[0041] The 1064nm laser first enters a Perinbroca prism 2, which is made of fused silica, causing the laser to be deflected by 90°. A 1064nm half-wave plate I3-1 and a 56° angled polarizer 4 are used together to adjust the output energy of the 1064nm laser. By rotating the angle of the half-wave plate I3-1, the energy of the P-beam transmitted through the 56° angled polarizer 4 is controlled, while the S-beam is reflected into the beam collector I5-1. The transmitted 1064nm laser is perpendicular to the beam. The laser beam is incident on a half-wave plate II3-2. The polarization direction of the 1064nm laser is adjusted by changing the angle of the 1064nm half-wave plate II3-2, ensuring that the KTP crystal's sixth-harmonic efficiency reaches over 50%. The frequency-doubled laser contains both 1064nm and 532nm laser beams. The 1064nm laser beam is transmitted through a 45° angle dichroic mirror I7-1 and collected by a beam collector II5-2. The reflected 532nm laser beam passes sequentially through the 45° angle dichroic mirror II7-1. 2. The square array vortex phase plate 8 and the square array focusing lens 9 reach the Raman cell 10. The laser beam is first shaped by the square array vortex phase plate 8 into four square array vortex beams. The square array focusing lens 9 focuses the vortex beams onto the center of the Raman cell 10. The Raman cell is filled with CH4 gas of 99.99% purity. Four square array annular spots are formed in the focal region, generating a 630nm backscattered Raman laser, a 630nm forward Raman laser, and the remaining 532nm pump laser. The forward 630nm and the remaining 532nm laser beams are absorbed by beam collector III5-3, while the 630nm backward Raman laser beam is first collimated by a square array focusing lens 9 and shaped by a square array vortex phase plate 8, resulting in a square beam shape, which is an approximately flat-top Gaussian beam with an energy of over 200mJ. It is output by a 45° dichroic mirror II7-2. Since backward Raman scattering has a phase compensation effect, a 630nm backward Raman laser beam with good beam quality can be obtained.

[0042] The Raman cell 10 is made of 304 stainless steel and has a total length of 14cm. Two windows, each 50mm in diameter and 10mm thick, are installed at either end of the Raman cell 10, designated as window I11-1 and window II11-2. The Raman cell is filled with 99.99% pure methane gas. The gas pressure inside the Raman cell 10 is adjustable, ranging from 0.5 to 4MPa. Before conducting the Raman test, the Raman cell 10 needs to be leak-tested and its internal air replaced to ensure the purity of the Raman gas and prevent leaks that could pose a hazard.

[0043] The half-wave plate I3-1 and the 56° angle polarization beam splitter 4 need to be used together to adjust the output energy of the 1064nm laser, and both optical components need to be coated with a 1064nm laser high-transmittance film.

[0044] The optical element half-wave plate II3-2 and KTP crystal 6 need to be used in combination. The half-wave plate II3-2 is used to adjust the polarization direction of the 1064nm laser, so that the second harmonic efficiency of the KTP crystal 6 can reach more than 50%. The surface of the half-wave plate II3-2 is coated with a 1064nm high-transmittance film, and the surface of the KTP crystal 6 is coated with high-transmittance films for both 1064nm and 532nm lasers.

[0045] The 45° angle dichroic mirror I7-1 can separate 1064nm and 532nm lasers, and the incident angle of the laser is 45°. The surface of the 45° angle dichroic mirror I7-1 is coated with a 1064nm laser high-transmittance film and a 532nm laser high-reflection film.

[0046] The 45° angle dichroic mirror II7-2 separates the 532nm frequency-doubled pump laser from the 630nm backscattered Raman laser, with the incident angle of the laser being 45°. The surface of the 45° angle dichroic mirror II7-2 is coated with a 532nm laser high-transmittance film and a 630nm laser high-reflection film.

[0047] The square array vortex phase plate 8 and the square array focusing lens 9 are coated with 532nm and 630nm high-transmittance laser coatings, respectively, with the square array focusing lens 9 having a focal length of 75mm.

[0048] The Raman cell 10 has windows made of fused silica at both ends, and the surfaces of windows I11-1 and II11-2 are coated with 532nm and 630nm high-transmittance laser films, respectively.

[0049] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0050] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0051] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0052] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0053] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0054] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[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-pulse-energy Raman laser under vortex optical pumping conditions, characterized in that, include: Pump laser (1), Perinbroka prism (2), half-wave plate I (3-1), 56° angle polarizing beam splitter (4), beam collector I (5-1), half-wave plate II (3-2), KTP crystal (6), 45° angle dichroic mirror I (7-1), beam collector II (5-2), 45° angle dichroic mirror II (7-2), square array vortex phase plate (8), square array focusing lens (9), Raman cell (10), and beam collector III (5-3); The Raman cell (10) includes: window I (11-1) and window II (11-2); the surfaces of both window I (11-1) and window II (11-2) are coated with a film system that has high transmission for both the pump laser wavelength and the first-order Stokes Raman laser wavelength. The pump laser (1) outputs a square flat-top Gaussian laser. Along the emission direction of the fundamental frequency laser, the Perinbroka prism (2), the half-wave plate I (3-1), the 56° angle polarizing beam splitter (4), the half-wave plate II (3-2), the KTP crystal (6), the 45° angle dichroic mirror I (7-1), the 45° angle dichroic mirror II (7-2), the square array vortex phase plate (8), the square array focusing lens (9), the Raman cell (10), and the beam collector III (5-3) are arranged in sequence. After the fundamental frequency laser is output from the pump laser (1), it first passes through the optical element Perinbroka prism (2), which folds the propagation direction of the fundamental frequency laser by 90°. The folded laser is then perpendicularly incident into half-wave plate I (3-1), and sequentially passes through 56° polarizing beam splitter (4), half-wave plate II (3-2), and KTP crystal (6) along the optical axis. The laser reflected by 56° polarizing beam splitter (4) is collected by beam collector I (5-1), and the KTP crystal is collected by 45° dichroic mirror I (7-1). After frequency doubling by the body (6), the frequency-doubled light and the remaining fundamental light are separated. The fundamental light is transmitted through a 45° dichroic mirror I (7-1), and the transmitted fundamental light is collected by beam collector II (5-2). The reflected frequency-doubled light is refracted by 90° and then transmitted sequentially through a 45° dichroic mirror II (7-2), a square array vortex phase plate (8), and a square array focusing lens (9). The frequency-doubled light is used as a pump laser and is focused by the square array focusing lens (9) onto the center of the Raman cell (10). The central focal region of the Raman cell (10) will show n 2 A square array is arranged with a ring focal point, n = 1, 2, 3..., generating forward stimulated Raman laser and backward stimulated Raman laser in the Raman cell (10). The forward Raman laser and the remaining pump laser are collected by beam collector III (5-3), while the backward first-order Stokes Raman laser is transmitted through the square array focusing lens (9) and the square array vortex phase plate (8), and is finally reflected and refracted 90° by the 45° angle dichroic mirror II (7-2) before being output. The 45° angle dichroic mirror II (7-2) plays the role of separating the pump laser and the backward Raman laser.

2. The miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions according to claim 1, characterized in that: The optical element half-wave plate I (3-1) is used in combination with the 56° angle polarization beam splitter (4) to adjust the output energy of the fundamental frequency laser, and the surface of the optical element is coated with a film system with high transmission of the fundamental frequency laser wavelength.

3. A miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions according to claim 1, characterized in that: The half-wave plate II (3-2) is used to adjust the polarization direction of the fundamental frequency laser. The surface of the half-wave plate II (3-2) is coated with a film system that has high transmission of the fundamental frequency laser wavelength. The surface of the KTP crystal (6) is coated with a film system that has high transmission of both the fundamental frequency laser wavelength and the frequency-doubled laser wavelength.

4. A miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions according to claim 1, characterized in that: The 45° angle dichroic mirror I (7-1) separates the fundamental frequency laser and the frequency-doubled laser, and the incident angle of the laser is 45°; the surface of the 45° angle dichroic mirror I (7-1) is coated with a film system that has high transmission of the fundamental frequency laser wavelength and high reflection of the frequency-doubled laser wavelength.

5. A miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions according to claim 1, characterized in that: The 45° angle dichroic mirror II (7-2) separates the frequency-doubled laser from the back-curved Raman laser, and the incident angle of the laser is 45°; the surface of the 45° angle dichroic mirror II (7-2) is coated with a film system that has high transmission of pump laser wavelength and high reflection of back-curved first-order Stokes Raman laser wavelength.

6. A miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions according to claim 1, characterized in that: The square array vortex phase plate (8) is a single optical element made of fused silica and formed by photolithography; the square array vortex phase plate (8) contains n 2 A square array of vortex phase plate elements, n = 1, 2, 3...; The topological charge l of each vortex phase plate unit remains consistent and is adjustable between l = 1 and l = 10. The surface of the square array vortex phase plate (8) is coated with a film system that has high transmission for both the pump laser wavelength and the backward first-order Stokes Raman laser wavelength.

7. A miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions according to claim 1, characterized in that: The square array focusing lens (9) is a single optical element made of fused silica and formed by photolithography; the square array focusing lens (9) contains n 2 A square array of focusing lens units is arranged, n = 1, 2, 3..., and the focal length of each focusing lens unit is consistent, between 60 and 130 mm. The center of the lens is collimated with the singularity of the center of the phase plate, and the surface of the square array focusing lens (9) is coated with a film system that has high transmission for both the pump laser wavelength and the back-directed first-order Stokes Raman laser wavelength.

8. A miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions according to claim 1, characterized in that: The Raman cell (10) is equipped with a pressure regulating valve and a pressure gauge on the outside of its base; The pressure regulating valve is used for the filling and releasing of Raman gas, and the pressure gauge is used to monitor the gas pressure inside the Raman cell (10) and whether there is leakage. The Raman cell (10) is filled with a Raman gas with a high backward Raman gain coefficient; the purity of the Raman gas is 99.99%; and the gas pressure in the Raman cell (10) is adjustable.

9. A miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions according to claim 1, characterized in that: The backscattered Raman laser generated in the Raman cell (10) returns along the original path and passes sequentially through the square array focusing lens (9) and the square array vortex phase plate (8). The square array focusing lens (9) is used for collimation of the backscattered Raman laser, and the square array vortex phase plate (8) shapes the vortex beam into a quasi-flat-top Gaussian beam. Since the backscattered Raman scattering process has a certain compensating effect on the phase change, the phase distribution of the beam is more uniform. Therefore, after collimation by the focusing lens and shaping by the vortex phase plate, a Raman laser with better beam quality is obtained.

10. A miniaturized high-pulse-energy Raman laser under vortex optical pumping conditions according to claim 1, characterized in that: The maximum energy of the backscattered Raman laser is obtained by optimizing parameters such as the pump laser energy, the topological charge of the square array vortex phase plate (8), the length of the Raman cell (10), the focal length of the square array focusing lens (9), and the pressure of the Raman gas. The laser power density in the focal region is greater than the threshold for backscattered Raman laser generation and less than the threshold for laser-induced breakdown. The output energy of the backscattered Raman laser reaches the level of hundreds of millijoules, and the total output energy is approximately equal to n times the Raman laser energy generated by each array unit. 2 Times, n = 1, 2, 3...

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