Laser beam synthesis device and method based on light field rotational symmetry

Abstract

The application provides a laser beam synthesis device and method based on light field rotational symmetry, and relates to the technical field of optics.The device comprises a laser generation module for generating N paths of double-lobe linear light beams with a central dark line;an orthogonal beam synthesis module comprising a strip mirror with a slit for coupling each group of orthogonal light beams in the N paths of double-lobe linear light beams, wherein one path of double-lobe linear light beams directly passes through the slit and maintains the double-lobe direction, and the other path of double-lobe linear light beams is reflected by the strip mirror to rotate the double-lobe direction by 90° to form a cross-shaped light spot with a central dark line; and a rotational symmetry beam synthesis module for coaxially superimposing N / 2 groups of orthogonal light beams to synthesize a petal-shaped light spot with a common central dark line and 2N peripheral bright petals.The device can flexibly control the beam shape without complex phase control in the laser beam synthesis process and effectively improve the far-field laser brightness.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to a laser beam synthesis device and method based on optical field rotational symmetry. Background Technology

[0002] With the increasing application of laser technology in industrial processing, national defense, cutting-edge science, and long-distance communication, increasingly stringent requirements are being placed on the output power, pulse energy, and beam quality of laser sources. However, due to factors such as thermal management, nonlinear effects, and material damage thresholds, there is a bottleneck in improving the power of a single laser. Laser beam combining technology has become the most direct and effective technical path to overcome this bottleneck. Its core idea is to combine multiple laser beams into a single output beam through a specific method, thereby achieving the superposition of power and energy, and even improving beam quality. In the field of high-power, high-energy lasers, applicable laser beam combining technologies mainly include coherent beam combining and incoherent beam combining.

[0003] Coherent beam combining requires all participating beams to maintain a constant phase relationship so that they interfere when superimposed in space. It mainly includes active phase-locked coherent beam combining and passive phase-locked coherent beam combining. Active phase-locked coherent beam combining splits a low-power, high-beam-quality seed source and injects it into multiple parallel channels for amplification. Each amplification channel is equipped with an independent phase detector and phase modulator. It has high beam combining efficiency, good beam quality, and is suitable for achieving extremely high-power coherent output, but the system is extremely complex and costly. Passive phase-locked coherent beam combining uses a shared external resonant cavity or diffractive optical elements to couple multiple laser units, achieving self-organized phase locking through optical feedback. Its structure is relatively simple and has good stability, but the number of scalable units is limited, and it is difficult to achieve kilowatt-level or higher high-power output.

[0004] Incoherent beam combining does not perform phase control on the laser units participating in the beam combining. It mainly achieves energy superposition through geometric or optical properties, and includes spatial beam combining, polarization beam combining, spectral beam combining, and temporal beam combining. Among them, polarization beam combining uses polarization beam splitters to combine two orthogonally linearly polarized beams into one beam, with extremely high beam combining efficiency, but it requires the input beam to be linearly polarized light and usually can only perform pairwise beam combining. Spectral beam combining uses multiple laser beams with slightly different emission wavelengths to pass through dispersive elements such as diffraction gratings, so that they exit at the same angle and overlap spatially. It can significantly improve the total power and maintain (or even slightly improve) the beam quality of individual emitting units. However, the system is complex, and the requirements for center wavelength stability, spectral linewidth control, and grating performance are extremely high. In addition, due to the need for wavelength selection, most of them use fiber optic structures, which makes it difficult to achieve high peak power carrying capacity. Timing-sequential beam combining utilizes a high-speed rotating disk to sequentially arrange multiple laser beams with a certain time delay and overlap them spatially. This can improve average power and total energy, but it usually does not change the single-pulse energy and peak power, and it introduces strong vibrations. Furthermore, it places certain requirements on the laser's repetition rate, making it difficult to match scenarios requiring high repetition rates and high stability. Traditional spatial side-by-side beam combining mainly relies on a combination of lenses and mirrors to tightly arrange multiple laser beams in space. While simple in principle, low in technical threshold, and capable of quickly achieving high power output, it increases the radius of the circumcircle, directly leading to a decrease in the brightness of the far-field spot, a corresponding increase in the beam parametric product, and a decrease in beam quality.

[0005] In summary, existing laser beam combining schemes generally suffer from drawbacks such as complex phase control, fixed beam shape, and poor compatibility. Summary of the Invention

[0006] This invention provides a laser beam combining device and method based on optical field rotational symmetry, which solves the problems of existing laser beam combining schemes, such as complex phase control, fixed beam shape and poor compatibility.

[0007] In one aspect, the present invention provides a laser beam combining device based on optical field rotational symmetry, comprising: The laser generation module is used to generate N double-lobed line beams with a central dark line. The double-lobed directions of each double-lobed line beam are arranged in rotation at angular intervals of π / N, where N is an even number greater than or equal to 4. The orthogonal beam combining module includes a strip-shaped reflector with a slit, used to couple each group of orthogonal beams in the N-way double-lobed line beams. One of the double-lobed line beams in each group of orthogonal beams passes directly through the slit and maintains the double-lobed direction, while the other double-lobed line beam changes direction after being reflected by the strip-shaped reflector to achieve collinear and coaxial transmission, forming a cross-shaped light spot with a central dark line. After the N-way double-lobed line beams are orthogonally combined by the orthogonal beam combining module, N / 2 cross-shaped light spots are obtained. The rotationally symmetric beam combining module includes orthogonal and hollow reflectors rotated by an angle of π / N, used to coaxially superimpose N / 2 sets of orthogonal beams to synthesize a petal-shaped light spot with a common central dark line and 2N peripheral bright lobes. Adjacent cross-shaped light spots have a relative rotation angle of π / N. The 2N peripheral bright lobes are distributed at equal angles on the same circumference on the output end face. The orthogonal and hollow reflectors rotated by an angle of π / N include cross-shaped hollow reflectors and / or star-shaped hollow reflectors.

[0008] In some embodiments, the laser generation module includes a stable-unstable hybrid resonant cavity and a scraper output mirror or a regionally coated lens. The scraper output mirror or the regionally coated lens is used to retain the central dark line region of the oscillating beam in the stable-unstable hybrid resonant cavity and continue to oscillate in the resonant cavity, and the upper and lower halves are coupled out to form the double-lobed line beam with a central dark line.

[0009] In some embodiments, the laser generation module is used to generate a one-dimensional HG01 Gaussian beam based on off-axis pumping or intracavity differential loss modulation, wherein the one-dimensional HG01 Gaussian beam is a double-lobed line beam with a central dark line.

[0010] In some embodiments, the laser generation module includes N laser generation units, each laser generation unit being used to generate a double-lobed line beam; In this configuration, each group of N laser generating units is placed in an orthogonal direction to form a group of orthogonal beams. Alternatively, the double-lobed line beam generated by one laser generating unit in each group of laser generating units undergoes orthogonal transformation through a periscope-type reflection module to form a group of orthogonal beams with the double-lobed line beam generated by another laser generating unit.

[0011] In some embodiments, the orthogonal beam combining module is further provided with a mirror group, which is used to control the optical path length of the two double-lobed line beams in each orthogonal beam group to be equal.

[0012] In some embodiments, both the orthogonal beam combining module and the rotationally symmetric beam combining module are composed of reflective optical elements.

[0013] In some embodiments, the single-lobed angular width of the aforementioned double-lobed line beam is not greater than π / 2N.

[0014] In another aspect, the present invention provides a laser beam synthesis method based on optical field rotational symmetry, comprising the following steps: The laser generation module generates N double-lobed line beams with a central dark line. The double-lobed directions of each double-lobed line beam are arranged in a rotating manner at angular intervals of π / N, where N is an even number greater than or equal to 4. The orthogonal beam combining module, which includes a strip-shaped reflector with a slit, couples each group of orthogonal beams in the N-path double-lobed line beams. One of the double-lobed line beams in each group passes directly through the slit and maintains the double-lobed direction, while the other double-lobed line beam changes direction after being reflected by the strip-shaped reflector to achieve collinear and coaxial transmission, forming a cross-shaped light spot with a central dark line. After the N-path double-lobed line beams are orthogonally combined by the orthogonal beam combining module, N / 2 cross-shaped light spots are obtained. A rotationally symmetric beam combining module, comprising orthogonal and hollow reflectors with a rotation angle of π / N, coaxially superimposes N / 2 sets of orthogonal beams to synthesize a petal-shaped light spot with a common central dark line and 2N peripheral bright lobes. Adjacent cross-shaped light spots have a relative rotation angle of π / N between them. The 2N peripheral bright lobes are distributed at equal angles on the same circumference on the output end face. The orthogonal and hollow reflectors with a rotation angle of π / N include cross-shaped hollow reflectors and / or star-shaped hollow reflectors.

[0015] In some embodiments, the orthogonal beam combining module is further provided with a mirror group, which is used to control the optical path length of the two double-lobed line beams in each orthogonal beam group to be equal.

[0016] In some embodiments, both the orthogonal beam combining module and the rotationally symmetric beam combining module are composed of reflective optical elements. Compared with the prior art, the present invention has the following significant advantages: The laser beam combining device based on optical field rotational symmetry provided in this application is a laser beam combining scheme that does not require phase control, can actively customize the shape of the output beam spot, and is naturally matched with the ring optical system. In this technical solution, N double-lobed line beams with a central dark line can be flexibly rearranged into a hollow petal-shaped beam with high energy utilization and a designable shape, avoiding complex phase control and flexibly controlling the beam shape; furthermore, since the near-field filling ratio of the double-lobed line beam with a central dark line is low, the rotational symmetry introduces N such beams without increasing the radius of the circumcircle of the near-field beam spot. N-way combining increases the near-field beam spot filling ratio by N times, and the corresponding far-field energy concentration is also improved, which can effectively improve the far-field laser brightness; furthermore, it also has high stability, wide pulse frequency compatibility, and good modular expansion potential. The above technical solution is particularly suitable for Cassegrain laser emission systems that have customized requirements for the shape of the light spot and require high light energy utilization. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this 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 this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the components of a laser beam combining device based on optical field rotational symmetry provided in an embodiment of this application; Figure 2 This is a schematic diagram illustrating the principle structure of an orthogonal beam combining module and a rotationally symmetric beam combining module provided in the embodiments of this application; Figure 3 This is a partial optical path diagram of an orthogonal beam combining module provided in an embodiment of this application; Figure 4 This is a schematic diagram of the path of a laser beam synthesis method based on optical field rotational symmetry provided in an embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] The laser beam combining apparatus and method based on optical field rotational symmetry provided by the present invention will be described in detail below with reference to the accompanying drawings. The embodiments of the present invention are intended to provide a deeper understanding of the technical solutions, but should not be construed as limiting the scope of protection. In the description of the present invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] The following is combined Figures 1 to 3 This application describes a laser beam combining apparatus based on optical field rotational symmetry provided in its embodiments.

[0022] Figure 1 A schematic diagram of a laser beam combining device based on optical field rotational symmetry provided in this application embodiment is shown below. Figure 1 As shown, the laser beam combining device based on optical field rotational symmetry includes a laser generation module 11, an orthogonal beam combining module 12, and a rotationally symmetric beam combining module 13.

[0023] Among them, the laser generation module 11 is used to generate N double-lobed line beams with a central dark line. The double-lobed directions of each double-lobed line beam are arranged in sequence at angular intervals of π / N. N is an even number greater than or equal to 4. In some embodiments, the value of N can be 4, 6, 8, 10, 12, etc. The orthogonal beam combining module 12 includes a strip-shaped reflector with a slit, used to couple each group of orthogonal beams in N double-lobed line beams. Each group of orthogonal beams includes two double-lobed line beams. The orthogonal beam combining module 12 can directly pass one double-lobed line beam in each group of orthogonal beams through the slit while maintaining the double-lobed direction. The other double-lobed line beam changes direction after being reflected by the strip-shaped reflector. Finally, each group of orthogonal beams can achieve collinear and coaxial transmission and form a cross-shaped light spot with a central dark line. After the N double-lobed line beams are orthogonally combined by the orthogonal beam combining module 12, N / 2 cross-shaped light spots can be obtained.

[0024] In some embodiments, the slit-shaped strip reflector described above can achieve orthogonal coupling of a set of orthogonal beams, that is, two orthogonal beams. For example, the slit-shaped strip reflector can be a 45° slit-shaped strip reflector. Typically, there is a 90° rotation angle between the two orthogonal beams. Therefore, one of the double-lobed line beams can pass directly through the slit and maintain its double-lobed direction, while the other double-lobed line beam is reflected by the 45° strip reflector and its double-lobed direction rotates by 90°, but the two beams still propagate collinearly and coaxially. Furthermore, the two beams will still have a 90° rotation angle, thus forming a cross-shaped near-field spatial distribution, which can be viewed as a cross-shaped light spot with a central dark line. For N double-lobed line beams forming N / 2 sets of orthogonal beams, after the first set of orthogonal beams forms the aforementioned cross-shaped light spot, the second set of orthogonal beams can also rotate clockwise at intervals of π / N degrees to form a cross-shaped light spot. In the case where N / 2 sets of orthogonal beams are formed from the above N beams, the final number of cross-shaped light spots is N / 2, and there is a relative rotation angle of π / N between adjacent cross-shaped light spots; The rotationally symmetric beam combining module includes an orthogonal and hollow reflector rotated by an angle of π / N, used to coaxially superimpose N / 2 cross-shaped light spots to synthesize a petal-shaped light spot with a common central dark line and 2N peripheral bright lobes. Adjacent cross-shaped light spots have a relative rotation angle of π / N. The aforementioned 2N peripheral bright lobes are distributed at equal angles on the same circumference on the output end face, thereby realizing the collinear and coaxial transmission of the aforementioned N double-lobed line beams.

[0025] In some cases, the aforementioned orthogonal and hollow reflectors with a rotation angle of π / N include cross-shaped hollow reflectors and / or star-shaped hollow reflectors. The cross-shaped hollow reflector can spatially synthesize two cross-shaped light spots by passing one cross-shaped light spot directly through and reflecting the other cross-shaped light spot, and then spatially synthesizing the two to obtain a star-shaped near-field spatial distribution. This star-shaped near-field spatial distribution can be regarded as obtaining a star-shaped light spot with a common dark line. When N equals 4, the final petal-shaped light spot with a central dark line and 2N outer bright lobes is a star-shaped light spot. For the star-shaped hollow reflector, it can be further synthesized with other types of light spots based on the star-shaped light spot to obtain a petal-shaped light spot with more outer bright lobes.

[0026] The laser beam combining device based on optical field rotational symmetry provided in this application provides a laser beam combining scheme that eliminates the need for phase control, allows for active customization of the output beam shape, and is naturally compatible with ring optics for N double-lobed line beams with a central dark line generated by the laser generation module 11. This scheme flexibly rearranges N double-lobed line beams with a central dark line into a hollow petal-shaped beam with high energy utilization and a designable shape, avoiding complex phase control and enabling flexible control of the beam shape. It effectively improves far-field laser brightness and exhibits high stability, wide pulse frequency compatibility, and good modular expansion potential. It is particularly suitable for Cassegrain laser emission systems that require customized beam shapes and high light energy utilization.

[0027] In some embodiments, the aforementioned laser generation module can obtain a double-lobed line beam with a central dark line in two ways. One way is that the laser generation module includes a stable-unstable hybrid resonant cavity and a scraper output mirror or a segmented coated mirror. The scraper output mirror or the segmented coated mirror is used to retain the central dark line region of the oscillating beam within the stable-unstable hybrid resonant cavity for continued oscillation, and the upper and lower halves are coupled and output to form a double-lobed line beam with a central dark line.

[0028] In another approach, the laser generation module is used to generate a one-dimensional HG01 Gaussian beam based on off-axis pumping or intracavity differential loss modulation. This one-dimensional HG01 Gaussian beam is a double-lobed line beam with a central dark line.

[0029] In some embodiments, the laser generation module described above may include N laser generation units, each laser generation unit generating one of the aforementioned double-lobed line beams. For cases requiring the generation of multiple sets of orthogonal beams, each of the N laser generation units may be placed in an orthogonal direction to form a set of orthogonal beams. Alternatively, the double-lobed line beam generated by one laser generation unit in each set of laser generation units may undergo orthogonal transformation via a periscope-type reflection module to form an orthogonal beam with the double-lobed line beam generated by another laser generation unit.

[0030] Figure 2 This application provides a schematic diagram illustrating the principle structure of an orthogonal beam combining module and a rotationally symmetric beam combining module. The structure and working principle of the orthogonal beam combining module 12 and the rotationally symmetric beam combining module 13 can be found in the following references. Figure 2 The content shown.

[0031] In this embodiment, the orthogonal beam combining module 12 described above may include a 45° strip-shaped reflector with a slit, and its working principle can be as follows: Figure 3 As shown, Figure 3 This is a partial optical path diagram of an orthogonal beam combining module provided in an embodiment of this application.

[0032] See Figure 2 and Figure 3 The slit direction of the 45° strip-shaped reflector with the slit is consistent with the direction of the double-lobed symmetry axis of the beam that passes directly through the slit. This allows the double-lobed line beam to pass directly through the reflector. In addition, the slit width is set to be less than or equal to the width of the central dark line, thereby ensuring that the beam that passes directly and the beam that is reflected do not overlap in energy within the central dark line region.

[0033] In some embodiments, the optical path lengths of two different double-lobed line beams in a set of orthogonal beams can be precisely controlled to be equal. Specifically, a mirror group can be provided in the orthogonal beam combining module 12. This mirror group is used to control the optical path lengths of the two double-lobed line beams in each set of orthogonal beams to be equal. The number of reflecting mirrors in the mirror group and the optical path lengths between the reflecting mirrors can be set according to actual needs, ultimately ensuring that the total optical path lengths of the two double-lobed line beams are equal. By controlling the total optical path length to be equal, the contrast of the final petal-shaped light spot can be controlled, the uniformity of the light spot can be improved, and wavefront (phase plane) matching can be ensured, achieving efficient focusing and creating conditions for forming an active stabilization system. exist Figure 2 In the embodiment shown, a cross-shaped hollow mirror is used to coaxially combine different numbers of cross-shaped light spots into the main optical path.

[0034] In this embodiment, the optical elements used in the orthogonal beam combining module 12 and the rotationally symmetric beam combining module 13 can all be reflective optical elements. By using all reflective optical elements to form a precise optical path, the double-lobed line beam with a central aperture can be rearranged into a circularly distributed petal-shaped hollow beam. The shape of the resulting petal-shaped hollow beam is highly matched with the annular receiving surface of the Cassegrain system, which can greatly improve the light energy utilization rate and the overall system efficiency, and solve the energy waste problem of traditional solid or messy beams.

[0035] The technical solution provided in this application embodiment can customize the shape of the light spot and the number of double-lobed line beams to be synthesized according to specific needs. As mentioned above, the value of N can be 4, 6, 8, 10 or 12, etc. When N=4, the laser generation module generates four double-lobed line beams with double-lobed directions of 0°, 45°, 90° and 135° respectively. After passing through the orthogonal beam combining module 12, two cross-shaped light spots with a relative rotation angle of 45° are formed. After being superimposed by the rotationally symmetric beam combining module 13, a star-shaped light spot with eight bright lobes is formed. When N is 6, 8, 10 or 12, the laser generation system generates a corresponding number of double-lobed line beams. The double-lobed direction intervals of adjacent beams are 30°, 22.5°, 18° or 15°, respectively. After passing through the orthogonal beam combining module 12, 3, 4 or 6 cross-shaped light spots are formed in sequence. After being superimposed by the rotationally symmetric beam combining module 13, petal-shaped light spots with 12, 16, 20 or 24 bright lobes are formed, respectively.

[0036] In this embodiment, the shape of each lobe in the double-lobed line beam can be customized according to actual needs, such as being straight or arc-shaped. The angular width of each lobe is no greater than π / 2N, so that the synthesized 2N bright lobes are evenly distributed on the circumference and that there is a clear dark area interval between adjacent bright lobes. The angular width of each lobe can be the angle corresponding to the symmetrical center point of each lobe's shape.

[0037] The technical solution provided in this application adopts a fully incoherent beam combining system, which is simple and reliable. It is based entirely on geometric optics reflection and arrangement, without any phase locking, wavelength selection or active modulation mechanism. The system has a simple structure, high stability, low cost and is not sensitive to environmental vibration.

[0038] Meanwhile, the above technical solution has no special requirements for the pulse frequency, wavelength, and coherence of the laser source, and is compatible with continuous wave and various repetition rate pulsed lasers. Furthermore, through a modular design, the total power can be flexibly adjusted by adding or removing beam combining units, offering significant expansion potential. In addition, the use of total internal reflection optical elements avoids the limitations of temperature drift, dispersion, and damage thresholds inherent in transmission elements (such as lenses and gratings), making it easier to achieve high average power and high peak power laser beam combining output.

[0039] In summary, the laser beam combining device based on optical field rotational symmetry provided in this application has creatively solved the pain points of "customization of specific spot shape" and "coupling of high-efficiency system" within the framework of incoherent beam combining, providing a stable, efficient, flexible and easy-to-engineer new approach to high-power laser beam combining for ring laser emission systems such as Cassegrain.

[0040] Corresponding to the laser beam combining device described above, this application also provides a corresponding laser beam combining method. Figure 4 A schematic flowchart of a laser beam synthesis method based on optical field rotational symmetry provided in this application embodiment is shown below. Figure 4 As shown, the method includes the following steps: Step 401: Generate N double-lobed line beams with a central dark line through the laser generation module. The double-lobed directions of each double-lobed line beam are arranged in rotation at angular intervals of π / N, where N is an even number greater than or equal to 4. Step 402: Couple each group of orthogonal beams in the N double-lobed line beams using an orthogonal beam combining module including a strip-shaped reflector with a slit. One double-lobed line beam in each group of orthogonal beams passes directly through the slit and maintains the double-lobed direction, while the other double-lobed line beam changes direction after being reflected by the strip-shaped reflector and forms a cross-shaped light spot with a central dark line. After the N double-lobed line beams are orthogonally combined by the orthogonal beam combining module, N / 2 cross-shaped light spots are obtained. Step 403: Using a rotationally symmetric beam combining module that includes orthogonal and hollow reflectors with a rotation angle of π / N, N / 2 sets of orthogonal beams are coaxially superimposed to synthesize a petal-shaped light spot with a common central dark line and 2N peripheral bright lobes. Adjacent cross-shaped light spots have a relative rotation angle of π / N. The 2N peripheral bright lobes are distributed at equal angles on the same circumference on the output end face. The orthogonal and hollow reflectors with a rotation angle of π / N include cross-shaped hollow reflectors and / or star-shaped hollow reflectors.

[0041] In some embodiments, the orthogonal beam combining module is further provided with a mirror group, which is used to control the optical path length of the two double-lobed line beams in each orthogonal beam group to be equal.

[0042] In some embodiments, both the orthogonal beam combiner module and the rotationally symmetric beam combiner module are composed of reflective optical elements. For details regarding this laser beam combining method, please refer to the above. Figures 1-3 The detailed description of the embodiments shown will not be repeated in this embodiment.

[0043] Based on the content described in the above embodiments, it can be understood that the technical solution of this application is laser beam synthesis based on the inherent central symmetry of a double-lobed line beam. The two bright lobes on either side of the central dark line beam are distributed 180° in diametrical alignment, much like on a clock face. In this technical solution, the laser generation module first outputs N (N is an even number not less than 4) double-lobed line beams. The "diametrical bright lobe pairs" of each double-lobed line beam are arranged in a rotating manner at π / N angular intervals, equivalent to arranging multiple sets of centrally symmetric beam pairs with different directions in parallel. Then, the N beams are grouped into pairs, and each group of orthogonal beams is orthogonally coupled through a 45° strip mirror with a slit. One beam passes directly through the slit, maintaining its original diametrical direction, while the other beam, after reflection, rotates its diametrical direction by 90°. The central dark areas of the two beams overlap. The two sets of opposing diameter bright lobes are orthogonal to each other and have no energy overlap, thus forming a cross-shaped light spot. This allows for the generation of N / 2 cross-shaped light spots with a relative rotation angle of π / N. Finally, through a non-plane reflector, such as a cross-shaped hollow reflector or a star-shaped hollow reflector, these N / 2 cross-shaped light spots are successively coaxially superimposed, so that each set of opposing diameter bright lobes is staggered at equal angles on the output end face, just like distributing multiple sets of opposing diameter scales at different angles evenly on the same circumference, ultimately synthesizing a rotationally symmetrical petal-shaped light spot with a central dark line and 2N outer bright lobes. For example, when N=4, an eight-lobed star-shaped light spot is formed. By expanding N to even numbers such as 6, 8, 10, and 12 and correspondingly narrowing the width of the single lobe angle, high-order rotationally symmetric light spots with 12, 16, 20, 24, or even more bright lobes can be obtained. The technical solution provided in this application embodiment can complete the spatial geometric arrangement by relying only on total internal reflection elements in the entire laser beam synthesis process, without the need for phase locking, wavelength selection, or active modulation.

[0044] 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser beam combining device based on the rotational symmetry of the optical field, characterized in that, include: The laser generation module is used to generate N double-lobed line beams with a central dark line. The double-lobed directions of each double-lobed line beam are arranged in rotation at angular intervals of π / N, where N is an even number greater than or equal to 4. The orthogonal beam combining module includes a strip-shaped reflector with a slit, used to couple each group of orthogonal beams in the N-way double-lobed line beams. One of the double-lobed line beams in each group of orthogonal beams passes directly through the slit and maintains the double-lobed direction, while the other double-lobed line beam changes direction after being reflected by the strip-shaped reflector and forms a cross-shaped light spot with a central dark line. After the N-way double-lobed line beams are orthogonally combined by the orthogonal beam combining module, N / 2 cross-shaped light spots are obtained. The rotationally symmetric beam combining module includes orthogonal and hollow reflectors rotated by an angle of π / N, used to coaxially superimpose N / 2 sets of orthogonal beams to synthesize a petal-shaped light spot with a common central dark line and 2N peripheral bright lobes. Adjacent cross-shaped light spots have a relative rotation angle of π / N. The 2N peripheral bright lobes are distributed at equal angles on the same circumference on the output end face. The orthogonal and hollow reflectors rotated by an angle of π / N include cross-shaped hollow reflectors and / or star-shaped hollow reflectors.

2. The apparatus according to claim 1, characterized in that, The laser generation module includes a stable-unstable hybrid resonant cavity and a scraper output mirror or a regionally coated lens. The scraper output mirror or the regionally coated lens is used to retain the central dark line region of the oscillating beam in the stable-unstable hybrid resonant cavity and continue to oscillate in the resonant cavity, and the upper and lower halves are coupled out to form the double-lobed line beam with a central dark line.

3. The apparatus according to claim 1, characterized in that, The laser generation module is used to generate a one-dimensional HG based on off-axis pumping or intracavity differential loss modulation. 01 Gaussian beam, the one-dimensional HG 01 A Gaussian beam is a double-lobed line beam with a central dark line.

4. The apparatus according to claim 1, characterized in that, The laser generation module includes N laser generation units, each laser generation unit being used to generate a double-lobed line beam; In this configuration, each group of N laser generating units is placed in an orthogonal direction to form a group of orthogonal beams. Alternatively, the double-lobed line beam generated by one laser generating unit in each group of laser generating units undergoes orthogonal transformation through a periscope-type reflection module to form a group of orthogonal beams with the double-lobed line beam generated by another laser generating unit.

5. The apparatus according to any one of claims 1-4, characterized in that, The orthogonal beam combining module is also equipped with a mirror group, which is used to control the optical path of the two double-lobed line beams in each orthogonal beam group to be equal.

6. The apparatus according to any one of claims 1-4, characterized in that, Both the orthogonal beam combiner module and the rotationally symmetric beam combiner module are composed of reflective optical elements.

7. The apparatus according to any one of claims 1-4, characterized in that, The single-lobed angular width of the double-lobed line beam is no greater than π / 2N.

8. A laser beam synthesis method based on optical field rotational symmetry, characterized in that, Includes the following steps: The laser generation module generates N double-lobed line beams with a central dark line. The double-lobed directions of each double-lobed line beam are arranged in a rotating manner at an angular interval of π / N, where N is an even number greater than or equal to 4. The orthogonal beam combining module, which includes a strip-shaped reflector with a slit, couples each group of orthogonal beams in the N-way double-lobed line beams. One of the double-lobed line beams in each group passes directly through the slit and maintains the double-lobed direction, while the other double-lobed line beam changes direction after being reflected by the strip-shaped reflector and forms a cross-shaped light spot with a central dark line. After the N-way double-lobed line beams are orthogonally combined by the orthogonal beam combining module, N / 2 cross-shaped light spots are obtained. A rotationally symmetric beam combining module, comprising orthogonal and hollow reflectors with a rotation angle of π / N, coaxially superimposes N / 2 sets of orthogonal beams to synthesize a petal-shaped light spot with a common central dark line and 2N peripheral bright lobes. Adjacent cross-shaped light spots have a relative rotation angle of π / N between them. The 2N peripheral bright lobes are distributed at equal angles on the same circumference on the output end face. The orthogonal and hollow reflectors with a rotation angle of π / N include cross-shaped hollow reflectors and / or star-shaped hollow reflectors.

9. The method according to claim 8, characterized in that, The orthogonal beam combining module is also equipped with a mirror group, which is used to control the optical path of the two double-lobed line beams in each orthogonal beam group to be equal.

10. The method according to claim 8, characterized in that, Both the orthogonal beam combiner module and the rotationally symmetric beam combiner module are composed of reflective optical elements.

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