Structured light generation device based on multi-core optical fiber beam combiner and preparation method

Abstract

The invention relates to the technical field of optical fiber lasers, in particular to a structured light generating device based on a multi-core optical fiber beam combiner and a preparation method, and the structured light generating device comprises an input multi-core optical fiber, a low-refractive-index sleeve, a mode conversion tapering region, a transition waist region and an output optical fiber which are connected in sequence, the transition waist area and the output optical fiber have the same number of optical fiber modes, and the mode conversion tapering area meets the adiabatic conversion condition. According to the invention, the multi-core optical fiber is adopted to replace a plurality of single-mode optical fibers in a traditional beam combiner, so that the generation of structured light with different amplitudes, phases and polarization states in the multi-core optical fiber is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber lasers, and more specifically, to a structured light generating device based on a multi-core optical fiber combiner and a preparation method thereof. Background Art

[0002] With the increasing demand for laser material processing, fiber-optic communication, etc., fiber lasers have gradually become one of the research hotspots in the laser field. Compared with traditional lasers, fiber lasers have the characteristics of high conversion efficiency, good beam quality, convenient thermal management and compact structure. In the application fields of industrial processing, optical communication, ranging, remote sensing and micro-processing, fiber lasers have broad prospects and have developed rapidly in recent years. In most application scenarios, by using fiber passive devices (such as fiber gratings, fiber combiners, etc.) to replace complex spatial optical components (such as lenses, reflectors), all-fiber lasers and laser amplifiers can be constructed, thereby effectively improving the stability of the system, simplifying the system structure, and making it easier to perform thermal management and ensure high beam quality. In industrial processing and specific transmission applications, people's demand for the output power of fiber lasers continues to increase. However, when the output power of a fiber laser increases to a certain extent, nonlinear effects such as stimulated Brillouin scattering and stimulated Raman effect will appear, making it difficult to continuously increase the power of the fiber laser.

[0003] In order to break through the output power limitation of a single fiber, scientists have proposed a solution to use beam synthesis technology to synthesize multiple medium-power fiber lasers into a higher-power laser. Among them, the coherent synthesis technology can maintain the quality of the laser beam while increasing the power and greatly improve the brightness of the light source, which has attracted widespread attention from scientific researchers. In the prior art, for example, Chinese patent CN117728287B discloses a method and device for improving the efficiency of laser coherent beam combining based on a photon lantern. Multiple single-mode optical fibers and capillaries are strictly arranged in a ring-shaped periodic manner from the inside to the outside to form a bundle. The bundle is placed in an outer sleeve and then melted and tapered into a few-mode optical fiber to form a photon lantern structure. The capillary becomes a photonic crystal after taper, and the two ends of the photon lantern structure are respectively fused with the first optical fiber and the second optical fiber. After phase control, multiple single-mode lasers are input from the single-mode optical fiber end of the photon lantern structure. After mode conversion and beam combining in the cone area of ​​the photon lantern structure, the multiple single-mode lasers are converted into a single-mode light beam, realizing the coherent beam combining of the laser. However, the device uses multiple single-mode optical fibers and can only combine them into a single-mode light with higher power. It is difficult to achieve coherent combination of lasers with different phases, polarization states, and amplitudes in multi-core optical fibers. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiency of the prior art that only simple fundamental mode light can be synthesized using multiple single-mode optical fibers, and it is difficult to achieve coherent combining of lasers with different phases, polarization states, and amplitudes. A structured light generating device and a preparation method based on a multi-core optical fiber combiner are provided to achieve coherent combining of lasers with various phases, polarization states, and amplitudes in a multi-core optical fiber.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A structured light combining device based on a multi-core optical fiber combiner is provided, characterized in that it comprises an input multi-core optical fiber, a low refractive index sleeve, a mode conversion taper region, a transition waist region and an output optical fiber connected in sequence, the phase, polarization state and amplitude of the laser in each core of the input multi-core optical fiber can be independently adjusted, the number of optical fiber modes between the transition waist region and the output optical fiber is the same, and the mode conversion taper region satisfies the adiabatic conversion condition, that is,

[0007]

[0008] Where β1 and β2 are the propagation constants of the two fiber modes that couple energy in the fiber core, r is the radial size of the adiabatic conversion tapered region, and z is the axial position of the adiabatic conversion tapered region.

[0009] The present invention discloses a structured light beam combining device based on a multi-core optical fiber combiner, which can synthesize structured light with different polarization, phase and amplitude distributions by regulating the phase, polarization and amplitude of the laser in the input multi-core optical fiber. In the laser beam combining process, Gaussian light with specific amplitude, phase and polarization is injected from each core in the input multi-core optical fiber and injected into the mode conversion taper region. In the mode conversion taper region, each input light generates coherent superposition and is converted into various different modes to propagate to the transition waist region, and finally conducts in the output optical fiber. When the mode conversion taper region meets the adiabatic conversion and mode matching conditions, the light beam can achieve efficient coupling and mode evolution when it is transmitted in the beam combiner structure of the mode conversion taper region. If the fundamental mode amplitude, phase and polarization of the input light beam are properly combined, different pure mode lasers can be obtained in the output optical fiber after the light beam passes through the multi-core optical fiber combiner. According to the type of structured light required in the output optical fiber, the phase, polarization and amplitude of the laser in each core in the input multi-core optical fiber can be adjusted, so as to generate different types of structured light at the output optical fiber.

[0010] Adiabatic conversion can ensure a smooth mode change process. The basic principle is that when the light beam passes through the adiabatic mode conversion taper area, the coupling and interference effects between the fiber cores are enhanced, thereby converting the light from one mode to another. The mode matching condition refers to the transition waist area in the combiner structure. The number of modes should be consistent with the number of modes in the output fiber, so that the transition waist area is also equivalent to a few-mode fiber, ensuring that the structured light synthesized in the mode conversion taper area can be stably transmitted to the output fiber, realizing the combination of various different structured lights in multi-core optical fibers.

[0011] Furthermore, the mode conversion tapered region is a truncated cone structure, and the diameter gradually decreases along the laser propagation direction. In the mode conversion tapered region, each fiber core gradually approaches each other in the propagation direction, and coupling is formed between the fiber cores to form a supermode, which is composed of the superposition of single modes of light with a certain amplitude and phase. As the mode conversion tapered region becomes thinner, the supermode further evolves into a certain mode or a superposition of several modes.

[0012] Furthermore, the core diameter and numerical aperture of the transition waist region are the same as those of the output optical fiber. The transition waist region matches the core diameter and numerical aperture of the output optical fiber to avoid partial laser scattering into the cladding structure of the output optical fiber and further reduce light transmission loss.

[0013] Furthermore, the number of cores in the input multi-core optical fiber is at least 3, and the positions of the cores are symmetrical about the axis of the input multi-core optical fiber. The use of a multi-core optical fiber with multiple cores inside can provide lasers of various amplitudes, phases, and polarization states for laser beam combining, and the symmetry between the cores is maintained to ensure the stability of the beam combining process in the mode conversion taper area, and finally the required structured light.

[0014] Furthermore, the cladding structure of the input multi-core optical fiber is a single cladding structure or a double cladding structure. The single cladding optical fiber is characterized by a small core diameter, and the optical signal can only propagate in one mode; the input multi-core optical fibers of the two cladding structures in the double cladding optical fiber can realize beam combining between multiple lasers in the mode conversion taper area, which can be adjusted according to the application scenario.

[0015] Furthermore, the refractive index profile type of the input multi-core optical fiber is a step type, a parabolic type, or a Gaussian type. In a step-index optical fiber, the refractive indexes of the core and the cladding are evenly distributed along the radial direction of the optical fiber, and at the interface between the core and the cladding, the refractive index changes in a step-shaped manner. This structure is relatively simple and low in cost, but it may produce dispersion during transmission, affecting signal quality. In a parabolic or Gaussian type, the refractive index of the core is not a uniform constant, but gradually decreases with the increase of the coordinate in the radial direction of the core, until it reaches a value equal to the refractive index of the cladding. This type of optical fiber can better control the propagation path of light, reduce dispersion, and provide more efficient signal transmission. The input multi-core optical fiber is compatible with these three types of refractive index profiles, and can be adaptively adjusted according to the actual use scenario to select the appropriate refractive index profile type.

[0016] The present invention also provides a method for preparing a structured light combining device based on a multi-core optical fiber combiner, comprising S1, cleaning the inner wall of the low-refractive index sleeve, and performing a pre-tapering process on the low-refractive index sleeve so that the inner diameter of the low-refractive index sleeve is slightly larger than the cladding diameter of the input multi-core optical fiber;

[0017] S2, removing the outer coating layer of the input multi-core optical fiber, cleaning the surface of the input multi-core optical fiber and inserting it into the low-refractive index sleeve, performing melt taper, and forming the mode conversion taper region and the transition waist region;

[0018] S3, cutting off the transition waist region, and fusing the transition waist region with the output optical fiber;

[0019] S4. The multi-channel laser light after phase, polarization and amplitude control is input from the input multi-core optical fiber, passes through the mode conversion tapered region and the transition waist region, and then outputs structured light from the output optical fiber.

[0020] The present invention discloses a preparation method of a structured light combining device based on a multi-core optical fiber combiner. First, a low-refractive index sleeve is pre-tapered to make the inner diameter of the sleeve slightly larger than the cladding diameter of the multi-core optical fiber. Subsequently, the multi-core optical fiber is stripped of its coating layer and inserted into the low-refractive index sleeve for melt taper to form a mode conversion taper region and a transition waist region. The optical fiber is cut from the transition waist region to keep the end face flat. Finally, the transition waist region is fused with the output few-mode optical fiber. Phase-controlled multi-path lasers are input from the input multi-core optical fiber end. After mode conversion is performed in the mode conversion taper region, the corresponding light beams are output from the output few-mode optical fiber. This realizes the combined generation of various structured lights in the multi-core optical fiber and reduces the process difficulty of the combiner structure.

[0021] Preferably, a large core diameter cutter is used to cut the transition waist region to keep the transition waist region cut surface flat. When cutting, care should be taken to keep the cut flat so that the transition waist region and the output optical fiber are smoothly fused and the loss during laser propagation is reduced.

[0022] Preferably, the core diameter of the input multi-core optical fiber is in the range of 4 to 30 μm, and the cladding diameter is in the range of 100 to 400 μm. The core diameter selection of the multi-core optical fiber will affect the transmission performance and manufacturing process of the optical fiber. Generally, the smaller the diameter, the lower the transmission loss of the optical fiber, but at the same time the higher the manufacturing cost. The cladding can protect the internal core wire from physical damage and environmental factors. When selecting the core diameter range and the core diameter range, it is necessary to take into account the optical fiber transmission loss, protection performance and production cost.

[0023] Preferably, the numerical aperture of the input multi-core optical fiber is in the range of 0.04 to 0.3. The numerical aperture of an optical fiber is an important parameter of a multimode optical fiber, which indicates the ability of the optical fiber end face to receive light and is a parameter that describes the ability of an optical fiber to collect light. A numerical aperture of 0.04 to 0.3 can control production costs while ensuring the transmission quality of light.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. It realizes the combination of laser beams with different amplitudes, phases, and polarization states in multi-core optical fibers, not limited to single-mode light;

[0026] 2. The multi-core optical fiber is used to replace the process of multiple single-mode optical fibers in the traditional combiner, which simplifies the preparation process and improves practicality;

[0027] 3. Adopting all-fiber connection, it has large communication capacity, high integration and space utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of a structured light generating device based on a multi-core optical fiber combiner;

[0029] Figure 2 This is a phase control test diagram of a structured light generating device based on a multi-core fiber combiner;

[0030] Figure 3 This is a polarization state control test diagram of a structured light generating device based on a multi-core fiber combiner;

[0031] Figure 4 Schematic diagram of the end face of the input multi-core optical fiber;

[0032] Figure 5 It is a flow chart of a method for preparing a structured light generating device based on a multi-core optical fiber combiner;

[0033] In the attached drawings: 100, input multi-core optical fiber; 200, low refractive index sleeve; 300, mode conversion taper region; 400, transition waist region; 500, output optical fiber. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0035] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] Embodiment 1

[0037] This embodiment is the first embodiment of a structured light generating device based on a multi-core fiber combiner, comprising an input multi-core fiber 100, a low refractive index sleeve 200, a mode conversion taper region 300, a transition waist region 400 and an output fiber 500 connected in sequence, wherein the phase, polarization state and amplitude of the laser in each core of the input multi-core fiber 100 can be independently controlled, the number of fiber modes between the transition waist region 400 and the output fiber 500 is the same, and the mode conversion taper region 300 satisfies the adiabatic conversion condition, i.e.

[0038]

[0039] Where β1 and β2 are the propagation constants of the two fiber modes that couple energy in the fiber core, r is the radial size of the adiabatic conversion tapered region, and z is the axial position of the adiabatic conversion tapered region.

[0040] When the light beam is transmitted in the multi-core fiber combiner structure of the device, efficient coupling and mode evolution can be achieved. If the input fundamental mode amplitude, phase and polarization state are properly combined, after the light beam passes through the multi-core fiber combiner, a variety of structured lights including vortex light, vector light and linear polarization LP mode described in other patents can be obtained. Figure 1As shown, multiple groups of lasers are input from the input multi-core optical fiber 100 into the laser beam combining device in this embodiment, and after passing through the low refractive index sleeve 200, beam combining occurs in the mode conversion taper region 300 of adiabatic conversion, and finally passes through the transition waist region 400 with the same number of modes and the output optical fiber 500, and structured light such as vortex light, vector light, and linear polarization LP mode can be obtained. Adiabatic conversion can ensure a smooth mode conversion process, and mode matching allows the combined optical fiber transmission to be stably conducted in the device.

[0041] In this embodiment, no special processing is required on the optical fiber structure, and the mode selection function of the photon lantern is not relied on. The coherent beam can be combined into structured light by adjusting the characteristics of the input laser. Figure 2 As shown, in this embodiment, a 6-core multi-core optical fiber is used, and a plurality of different phase vortex lights are generated by adjusting the laser phase in each optical fiber in the input multi-core optical fiber 100. Figure 3 As shown, the arrows in the figure indicate the polarization directions of the lasers in each optical fiber in the input multi-core optical fiber 100. By changing the polarization states of each laser, various types of structured lights required can be combined.

[0042] The mode conversion taper region 300 in this embodiment is a truncated cone structure, and its diameter gradually decreases along the laser propagation direction. Figure 1 As shown, in the truncated cone-shaped mode conversion tapered region 300, the diameter of the input multi-core optical fiber 100 is continuously reduced, the optical fiber's ability to bind light is reduced, and the light gradually escapes to the middle of the cladding for transmission. At this time, a new waveguide structure is formed in the mode conversion tapered region 300, and the cladding of the input multi-core optical fiber 100 becomes the core of the new waveguide structure, and the low-refractive index sleeve 200 serves as the cladding of the new waveguide structure. Each core gradually approaches in the propagation direction, and coupling is formed between the cores to form a supermode. As the mode conversion tapered region 300 becomes thinner, the supermode further evolves into a certain mode or a superposition of several modes.

[0043] The core diameter and numerical aperture of the transition waist region 400 are the same as those of the output optical fiber 500. The transition waist region 400 is essentially equivalent to a few-mode optical fiber, and its core diameter is the same as that of the output optical fiber 500, so that all the combined light can enter the output optical fiber 500, avoiding light spilling into the cladding structure of the output optical fiber 500. In the field of optical fiber, the numerical aperture describes the cone angle size when light enters and exits the optical fiber. The transition waist region 400 matches the numerical aperture of the output optical fiber 500, which can further reduce the transmission loss of light in the device.

[0044] The working principle of the structured light generating device based on the multi-core fiber combiner in this embodiment is as follows: multiple groups of lasers are input from the input multi-core optical fiber 100, and enter the mode conversion tapered area 300 of adiabatic conversion after passing through the low refractive index sleeve 200. In the mode conversion tapered area 300, each fiber core slowly approaches each other to form a new waveguide structure, evolving into a certain mode or a superposition of several modes, and finally passing through the transition waist area 400 with the same mode number, core diameter, and numerical aperture, and the output optical fiber 500, and finally outputting a specific structured light.

[0045] Embodiment 2

[0046] This embodiment is a second embodiment of a structured light generating device based on a multi-core fiber combiner. This embodiment is similar to the first embodiment, except that the number of cores in the input multi-core fiber 100 is at least 3, and the positions of the cores are symmetrical about the axis of the input multi-core fiber 100. Figure 4 As shown, the input multi-core optical fiber 100 in this embodiment can adopt a 7-core structure, with one core located at the axis of the input multi-core optical fiber 100, and the remaining cores are evenly arranged in a circular shape around it. Such a multi-core optical fiber with a centrally symmetrical structure provides a variety of position options for laser synthesis, ensures the stability of its beam combining process, and finally outputs various types of structured light.

[0047] The cladding structure of the input multi-core optical fiber 100 is a single-cladding structure or a double-cladding structure. The single-cladding optical fiber is characterized by a small core diameter, and the optical signal can only propagate along one mode, which reduces the mode dispersion, thereby providing clear signal transmission in long-distance and high-bandwidth applications; the inner layer of the double-cladding optical fiber is used to transmit the signal, and the outer layer is used to transmit the pump light. This design makes the double-cladding optical fiber more efficient in light amplification and long-distance transmission. Both cladding structures of the input multi-core optical fiber 100 can realize the combination of multiple structured lights in the mode conversion taper region 300, which can be adjusted according to the application.

[0048] The refractive index profile type of the input multi-core optical fiber 100 is step-index, parabolic or Gaussian. The refractive index of the step-index optical fiber changes in a step-like manner between the core and the cladding, while the refractive index of the gradient optical fiber changes gradually along the radial direction. Both parabolic and Gaussian optical fiber refractive index profiles belong to gradient optical fibers, in which the Gaussian refractive index change follows the Gaussian distribution, that is, the refractive index gradually decreases with the increase of the radius. The gradient refractive index profile can reduce the mode dispersion in the optical fiber, increase the transmission capacity of the optical fiber, and optimize the beam quality, so that the optical signal can maintain a higher stability during the transmission process, but at the same time the production cost is high. Step refractive index optical fiber is suitable for short-distance, low-rate data transmission, while parabolic and Gaussian optical fibers are more suitable for long-distance, high-rate data transmission, especially in communication systems that require high bandwidth and low loss. The structured light generating device based on the multi-core optical fiber combiner in this embodiment does not limit the refractive index profile type of the input multi-core optical fiber 100, and can be selected according to needs, and its application occasions are more extensive.

[0049] The working principle of the structured light generating device based on the multi-core fiber combiner in this embodiment is as follows: the input multi-core optical fiber 100 contains at least three symmetrically distributed optical cores, and different refractive index profile types and laser phases can be selected in the input multi-core optical fiber 100 according to the application scenario of the device and the type of structured light ultimately required.

[0050] Embodiment 3

[0051] This embodiment is the first embodiment of a method for preparing a structured light generating device based on a multi-core optical fiber combiner, comprising S1, cleaning the inner wall of a low-refractive index sleeve 200, and performing a pre-tapering process on the low-refractive index sleeve 200, so that the inner diameter of the low-refractive index sleeve 200 is slightly larger than the cladding diameter of the input multi-core optical fiber 100;

[0052] S2, removing the outer coating layer of the input multi-core optical fiber 100, cleaning the surface of the input multi-core optical fiber 100 and inserting it into the low-refractive index sleeve 200, performing melt taper, and forming a mode conversion taper region 300 and a transition waist region 400;

[0053] S3, cutting off the transition waist region 400, and fusing the transition waist region 400 with the output optical fiber 500;

[0054] S4. After phase control, the multi-channel lasers are input from the input multi-core optical fiber 100, and after passing through the mode conversion tapered region 300 and the transition waist region 400, the combined single-mode lasers are output from the output optical fiber 500.

[0055] like Figure 5As shown, in step S1, the low refractive index sleeve 200 needs to be cleaned by ultrasonic cleaning. When pre-tapering the low refractive index sleeve 200, it is necessary to make the inner diameter of the sleeve slightly larger than the cladding diameter of the input multi-core optical fiber 100 to facilitate the subsequent insertion of the input multi-core optical fiber 100 into the low refractive index sleeve 200.

[0056] In step S2, the input multi-core optical fiber 100 needs to be cleaned with alcohol after removing the outer coating layer to ensure that it will not be interfered by impurities during the transmission process. Then, the low refractive index sleeve 200 is adiabatically tapered using LZM-100 to obtain the mode conversion taper region 300 and the transition waist region 400. The length of the taper can be determined by the simulation software Rsoft. The software is used to calculate the value of the taper length when the input coupling efficiency is the highest and the output mode accounts for the highest proportion when the same type of light is input, and the taper length and taper ratio can be obtained.

[0057] In step S3, the cut transition waist region 400 is fused with the output optical fiber 500, and attention is paid to ensuring the alignment of the fiber cores, so that a complete structured light generating device based on a multi-core optical fiber combiner can be obtained.

[0058] In this embodiment, a large core diameter cutter is used to cut the transition waist region 400 to keep the transition waist region 400 with a smooth cut surface. The transition waist region 400 with a smooth cut surface is easier to be fused with the output optical fiber 500, reducing the loss during light propagation.

[0059] The core diameter of the input multi-core optical fiber 100 ranges from 4 to 30 μm, and the cladding diameter ranges from 100 to 400 μm. In this embodiment, the core diameter of the input multi-core optical fiber 100 can be selected to be 8.2 μm, and the cladding diameter is 150 μm. The material is generally quartz or quartz-doped material, and the laser wavelength is around 1 nm. In order to ensure the transmission performance of the optical fiber, a core diameter greater than 30 μm should not be selected. At the same time, the manufacturing cost needs to be controlled so that the core diameter is greater than 4 μm, which can take into account both transmission loss and production cost. The main function of the cladding is to protect the internal core wire from external physical damage and environmental factors. Selecting quartz material and controlling its diameter range can provide good protection without significantly increasing production costs.

[0060] The numerical aperture of the input multi-core optical fiber 100 ranges from 0.04 to 0.3. The numerical aperture of the input multi-core optical fiber 100 in this embodiment can be selected as 0.13. The numerical aperture of the optical fiber is an important parameter of the multimode optical fiber. It indicates the ability of the optical fiber end face to receive light and is a parameter that describes the ability of the optical fiber to collect light. The numerical aperture of 0.04 to 0.3 can take into account both the transmission quality of light and the production cost.

[0061] The working principle of the preparation method of the structured light generating device based on the multi-core fiber combiner in this embodiment is as follows: first, the inner wall of the low-refractive index sleeve 200 is cleaned and the low-refractive index sleeve 200 is pre-tapered, and then the multi-core optical fiber 100 is input and the coating layer is stripped, and then inserted into the pre-tapered low-refractive index sleeve 200 for melt taper to form a mode conversion taper region 300 and a transition waist region 400, and then cut off from the transition waist region 400 and fused with the output optical fiber 500, and finally, the phase-controlled multi-channel laser is input from the input multi-core optical fiber 100, and the corresponding light beam is output from the output optical fiber 500 after mode conversion through the mode conversion taper region 300.

[0062] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A structured light generating device based on a multi-core optical fiber combiner, characterized in that: The invention comprises an input multi-core optical fiber (100), a low refractive index sleeve (200), a mode conversion tapered region (300), a transition waist region (400) and an output optical fiber (500) which are connected in sequence. The phase, polarization state and amplitude of the laser in each core of the input multi-core optical fiber (100) can be independently adjusted. The number of optical fiber modes between the transition waist region (400) and the output optical fiber (500) is the same. The mode conversion tapered region (300) satisfies the adiabatic conversion condition, that is, Wherein β1 and β2 are propagation constants of two optical fiber modes for energy coupling in the fiber core, r is the radial dimension of the adiabatic conversion tapered region (300), and z is the axial position of the adiabatic conversion tapered region (300).

2. The structured light generating device based on a multi-core optical fiber combiner according to claim 1, characterized in that: The mode conversion tapered region (300) is a truncated cone structure, and its diameter gradually decreases along the laser propagation direction.

3. The structured light generating device based on a multi-core optical fiber combiner according to claim 1, characterized in that: The transition waist region (400) matches the core diameter and numerical aperture of the output optical fiber (500).

4. The structured light generating device based on a multi-core optical fiber combiner according to claim 1, characterized in that: The number of fiber cores in the input multi-core optical fiber (100) is at least 3, and the positions of the fiber cores are symmetrical about the axis of the input multi-core optical fiber (100).

5. The structured light generating device based on a multi-core optical fiber combiner according to claim 1, characterized in that: The cladding structure of the input multi-core optical fiber (100) is a single cladding structure or a double cladding structure.

6. The structured light generating device based on a multi-core optical fiber combiner according to claim 1, characterized in that: The refractive index profile type of the input multi-core optical fiber (100) is a step type, a parabola type or a Gaussian type.

7. A method for preparing a structured light generating device based on a multi-core optical fiber combiner, used for preparing a structured light combining device based on a multi-core optical fiber combiner as claimed in any one of claims 1 to 6, characterized in that: include: S1, cleaning the inner wall of the low refractive index sleeve (200), and performing a pre-tapering process on the low refractive index sleeve (200), so that the inner diameter of the low refractive index sleeve (200) is slightly larger than the cladding diameter of the input multi-core optical fiber (100); S2, removing the outer coating layer of the input multi-core optical fiber (100), cleaning the surface of the input multi-core optical fiber (100), inserting it into the low refractive index sleeve (200), and performing melt taper to form the mode conversion taper region (300) and the transition waist region (400); S3, cutting off the transition waist region (400), and fusing the transition waist region (400) with the output optical fiber (500); S4, the multi-path laser light after the amplitude, phase and polarization state are jointly regulated is input from the input multi-core optical fiber (100), passes through the mode conversion tapered region (300) and the transition waist region (400), and then is output from the output optical fiber (500) to complete the combined laser light.

8. The method for preparing a structured light generating device based on a multi-core optical fiber combiner according to claim 7, characterized in that: In S3, a large core diameter cutting knife is used to cut the transition waist region (400) to keep the cross section of the transition waist region (400) smooth.

9. The method for preparing a structured light generating device based on a multi-core optical fiber combiner according to claim 7, characterized in that: In S1, the core diameter of the input multi-core optical fiber (100) is in the range of 4 to 30 μm, and the cladding diameter is in the range of 100 to 400 μm.

10. The method for preparing a structured light generating device based on a multi-core optical fiber combiner according to claim 7, characterized in that: In S1, the numerical aperture of the input multi-core optical fiber (100) is in the range of 0.04 to 0.3.

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