Multi-core optical fiber beam combining system based on multi-plane light conversion

Abstract

The invention discloses a multi-core optical fiber beam combining system based on multi-plane light conversion. Comprising a laser light source, a phase polarization controller, an input multi-core optical fiber, a beam expander and a multi-plane light converter which are arranged on the same parallel line, the phase polarization controller is used for independently adjusting the phase and polarization state of a light beam which is incident from a laser light source to the input multi-core optical fiber and is output from each fiber core in the input multi-core optical fiber; the beam expander is used for amplifying and collimating a light beam output by the input multi-core optical fiber; and the multi-plane light converter is used for performing multiple phase transformations and optical Fourier transformations on the expanded and collimated light beams, and finally outputting structural light beams with specific intensity distribution, phase distribution and polarization distribution. According to the system, laser beam combination of different amplitudes, phases and polarizations in the multi-core optical fiber can be achieved, laser beam combination of input optical fibers of different types and arrangements is achieved at the same time, and the expansibility and mode coupling efficiency of optical fiber beam combination are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber lasers, and particularly to a multi-core fiber beam combining system based on multi-plane light conversion. Background Art

[0002] At present, ultrashort pulse lasers are widely used in fields such as material processing, high-energy physics, laser weapons, and free-space optical communication due to their advantages of high energy and high beam quality. With the advancement of precision in the manufacturing field and the further development of the national defense industry, the demand for lasers with higher power and higher quality is increasing day by day. Although a single fiber laser can obtain a higher power output by optimizing its structure, its improvement is limited due to factors such as fiber nonlinear effects and thermal damage. To solve this problem, the coherent beam combining technology of lasers has emerged, which can obtain a higher power laser output by coherently combining several medium-power lasers.

[0003] Coherent synthesis technology can generally be divided into common-aperture synthesis and separate-aperture synthesis. Common-aperture synthesis forms a single laser output by making the laser beams of each path completely overlap in space, combining the laser beams of each path into one beam in the near field, so there are no side lobes in the far field, but there is energy loss during the beam combining process; separate-aperture synthesis reduces the energy proportion of side lobes in the far-field spot of the array beam by compressing the duty cycle of the array beam, which is a tight splicing of the laser beams of each path, and there is no energy loss during the synthesis process, but the energy of the far-field spot will disperse to the side lobes, resulting in energy loss of the central main spot, and the theoretical upper limit of the beam combining efficiency is only 60% to 70%.

[0004] As a new optical technology, multi-plane light conversion has the characteristics of low loss, efficient mode conversion, and high flexibility. It consists of multiple phase plates or spatial light modulators, and realizes precise phase control through continuous phase transformation and optical transformation.

[0005] The prior art has proposed an optical device for synthesizing multiple beams and a system using the optical device. The optical device includes a conversion device disposed between an input plane and an output plane. The conversion device is configured to perform mode conversion, and the mode conversion is intended to transfer an energy portion of the incident radiation existing in the main supermode to a target mode, and is intended to transfer an energy portion of the incident radiation existing in the coherent supermode to a deformed mode. However, this device uses multiple single-mode fibers and can only combine into structured light with a small number of modes, resulting in low expandability and making it difficult to realize the laser beam combining of input fibers with different types and arrangements. Summary of the Invention

[0006] In order to overcome the problem that in the process of fiber beam combination in the prior art, only structured light with a small number of modes can be combined, and the scalability is low, resulting in difficulty in realizing the laser beam combination of input fibers of different types and arrangements, the object of the present invention is to propose a multi-core fiber beam combination system based on multi-plane light conversion, which can realize the laser beam combination of various lasers with different amplitudes, phases and polarizations in multi-core fibers. At the same time, the laser beam combination of input fibers of different types and arrangements is realized, and the scalability and mode coupling efficiency of fiber beam combination are improved.

[0007] To achieve the object of the present invention, the present invention is implemented by the following technical solutions:

[0008] A multi-core fiber beam combination system based on multi-plane light conversion, the system includes:

[0009] A laser light source, a phase polarization controller, an input multi-core fiber, a beam expander and a multi-plane light converter arranged on the same parallel line;

[0010] The light source output end of the laser light source is connected to the input end of the phase polarization controller, the output end of the phase polarization controller is connected to the input end of the input multi-core fiber, the output end of the input multi-core fiber is connected to the input end of the beam expander, and the output end of the beam expander is connected to the input end of the multi-plane light converter;

[0011] The phase polarization controller is used to independently adjust the phase and polarization state of the light beam incident from the laser light source to the input multi-core fiber and output from each core of the input multi-core fiber;

[0012] The beam expander is used to amplify and collimate the light beam output from the input multi-core fiber;

[0013] The multi-plane light converter is used to perform multiple phase transformations and optical Fourier transforms on the expanded and collimated light beam, and finally output a structured light beam with a specific intensity distribution, phase distribution and polarization distribution.

[0014] In the above technical solution, by using a phase polarization controller to independently adjust the phase and polarization state of the light beam output from each core in the input multi-core optical fiber, laser beam combination with various different amplitudes, phases, and polarizations in the multi-core optical fiber can be achieved, no longer limited to single-mode optical fibers. At the same time, the beam expander is used to amplify and collimate the light beam output from the input multi-core optical fiber, and then combined with the multi-plane optical converter to perform multiple phase transformations and optical Fourier transforms on the expanded and collimated light beam, finally outputting a structured light beam with a specific intensity distribution, phase distribution, and polarization distribution, thereby realizing the laser beam combination of input optical fibers with different types and arrangements, improving the expandability of fiber beam combination, and through the combination of the above components and the design of the positional relationship, the components can have high stability, thereby improving the efficiency of mode coupling.

[0015] Preferably, the multi-plane optical converter includes a phase plate and a mirror arranged in parallel, and the beam is reflected multiple times through the parallel arrangement structure.

[0016] Preferably, the phase plate is a spatial light modulator or a fixed phase plate, and its surface phase distribution is programmable or fixed, and is used to apply a predetermined phase modulation to the incident light beam.

[0017] Preferably, the distance between the phase plate and the mirror is adjustable to generate structured light beams with different wavelengths or different modes.

[0018] Preferably, the system dynamically switches the mode type of the output structured light beam by adjusting the phase distribution parameters of the phase plate.

[0019] Preferably, the beam expander includes a lens group and a microlens array, and is used to adjust the size and collimation of the light beam to meet the incident conditions of the multi-plane optical converter.

[0020] Preferably, the number of reflections of the multi-plane optical converter is two or more, and the coherent beam combination and mode conversion of the light beam are realized through the optical Fourier transform during the reflection process.

[0021] In the above technical solution, considering the laser beam combination of input optical fibers with different types and arrangements, the structures of the phase plate and the mirror in the multi-plane optical converter are designed to be parallel to each other, and the distance between the phase plate and the mirror is adjustable to generate structured light beams with different wavelengths or different modes, so that the system can dynamically switch the mode type of the output structured light beam by adjusting the phase distribution parameters of the phase plate; and the phase plate is designed as a spatial light modulator or a fixed phase plate, and its surface phase distribution is programmable or fixed, so that a predetermined phase modulation can be effectively applied to the incident light beam, improving the expandability of fiber beam combination and the mode coupling efficiency.

[0022] Preferably, the number of cores of the input multi-core optical fiber includes one or more combinations of four cores, six cores, eight cores or ten cores, and the number of input multi-core optical fibers includes a single fiber or multiple fibers arranged in parallel.

[0023] Preferably, the light beams output from each core in the input multi-core optical fiber are independently controlled by a phase polarization controller, so that the modes of the output structured light beams include but are not limited to LP01, LP11, LP21, LP31, OAM-1 or OAM-2 modes.

[0024] Preferably, the transverse light field distribution, phase distribution and polarization distribution of the structured light beam are jointly determined by the amplitudes, phase differences and polarization states of the light beams of each core in the input multi-core optical fiber.

[0025] In the above technical solution, designing the number of cores of the input multi-core optical fiber as one or more combinations of four cores, six cores, eight cores or ten cores, and the number of input multi-core optical fibers including a single fiber or multiple fibers arranged in parallel can generate structured light beams with different transverse phases, polarizations and light field distributions.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The present invention provides a multi-core fiber beam combining system based on multi-plane light conversion. By independently adjusting the phase and polarization states of the light beams output from each core in the input multi-core optical fiber through a phase polarization controller, the laser beam combination of various different amplitudes, phases and polarizations in the multi-core optical fiber can be realized, no longer limited to single-mode optical fibers. At the same time, the beam expander is used to amplify and collimate the light beam output from the input multi-core optical fiber, and then combined with the multi-plane optical converter to perform multiple phase transformations and optical Fourier transforms on the expanded and collimated light beam, and finally output a structured light beam with a specific intensity distribution, phase distribution and polarization distribution, thereby realizing the laser beam combination of input optical fibers with different types and arrangements, improving the expansibility of fiber beam combination, and through the combination of the above components and the design of the positional relationship, the components can have high stability, thereby improving the efficiency of mode coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural block diagram of a multi-core fiber beam combining system based on multi-plane light conversion provided by an embodiment of the present application;

[0029] Figure 2 It is a schematic diagram of multi-core optical fibers with different numbers of cores used in the experiment provided by an embodiment of the present application;

[0030] Figure 3 It is a schematic diagram of multi-core optical fibers with different numbers of fibers used in the experiment provided by an embodiment of the present application;

[0031] Figure 4Schematic diagram of the six-core optical fiber used in the experiment provided by the embodiments of the present application;

[0032] Figure 5 Schematic diagram of the LP01 mode of the light output from the six-core optical fiber in the experiment provided by the embodiments of the present application;

[0033] Figure 6 Schematic diagram of the LP11 mode of the light output from the six-core optical fiber in the experiment provided by the embodiments of the present application;

[0034] Figure 7 Schematic diagram of the LP21 mode of the light output from the six-core optical fiber in the experiment provided by the embodiments of the present application;

[0035] Figure 8 Schematic diagram of the LP31 mode of the light output from the six-core optical fiber in the experiment provided by the embodiments of the present application;

[0036] Figure 9 Schematic diagram of the OAM-1 mode of the light output from the six-core optical fiber in the experiment provided by the embodiments of the present application;

[0037] Figure 10 Schematic diagram of the OAM-2 mode of the light output from the six-core optical fiber in the experiment provided by the embodiments of the present application;

[0038] In the figure: 1 - laser light source; 2 - phase polarization controller; 3 - input multi-core optical fiber; 4 - beam expander; 5 - multi-plane optical converter, 51 - phase plate, 52 - mirror. Detailed implementation manners

[0039] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0040] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0042] Embodiment 1:

[0043] This embodiment provides a multi-core fiber beam combining system based on multi-plane light conversion. Refer to Figure 1 , the system includes:

[0044] A laser light source 1, a phase polarization controller 2, an input multi-core fiber 3, a beam expander 4, and a multi-plane light converter 5 arranged on the same parallel line;

[0045] The light source output end of the laser light source 1 is connected to the input end of the phase polarization controller 2, the output end of the phase polarization controller 2 is connected to the input end of the input multi-core fiber 3, the output end of the input multi-core fiber 3 is connected to the input end of the beam expander 4, and the output end of the beam expander 4 is connected to the input end of the multi-plane light converter 5;

[0046] The phase polarization controller 2 is used to independently adjust the phase and polarization state of the light beam incident from the laser light source 1 to the input multi-core fiber 3 and output from each core of the input multi-core fiber 3;

[0047] The beam expander 4 is used to amplify and collimate the light beam output from the input multi-core fiber 3;

[0048] The multi-plane light converter 5 is used to perform multiple phase transformations and optical Fourier transforms on the expanded and collimated light beam, and finally output a structured light beam with a specific intensity distribution, phase distribution, and polarization distribution.

[0049] In this embodiment, by independently adjusting the phase and polarization state of the light beam output from each core of the input multi-core fiber 3 through the phase polarization controller 2, the laser beam combination of various different amplitudes, phases, and polarizations in the multi-core fiber can be realized, no longer limited to single-mode fibers. At the same time, the beam expander 4 is used to amplify and collimate the light beam output from the input multi-core fiber 3, and then combined with the multi-plane light converter 5 to perform multiple phase transformations and optical Fourier transforms on the expanded and collimated light beam, and finally output a structured light beam with a specific intensity distribution, phase distribution, and polarization distribution, thereby realizing the laser beam combination of input fibers with different types and arrangements, improving the expandability of fiber beam combination, and through the combination of the above components and the design of the positional relationship, it can ensure that the components have high stability, thereby improving the efficiency of mode coupling.

[0050] Embodiment 2:

[0051] This embodiment is further described based on the beam expander 4 and the multi-plane optical converter 5 in Embodiment 1, as follows:

[0052] As a preferred embodiment, refer to Figure 1 , the multi-plane optical converter 5 includes a phase plate 51 and a mirror 52 arranged in parallel, and the beam is reflected multiple times through the parallel arrangement structure.

[0053] As a preferred embodiment, the phase plate 51 is a spatial light modulator or a fixed phase plate, and its surface phase distribution is programmable or fixed, and is used to apply a predetermined phase modulation to the incident beam.

[0054] As a preferred embodiment, the distance between the phase plate 51 and the mirror 52 is adjustable to generate structured light beams of different wavelengths or different modes.

[0055] As a preferred embodiment, the system dynamically switches the mode type of the output structured light beam by adjusting the phase distribution parameters of the phase plate 51.

[0056] As a preferred embodiment, the transverse optical field distribution, phase distribution, and polarization distribution of the structured light beam are jointly determined by the amplitudes, phase differences, and polarization states of the light beams in each core of the input multi-core optical fiber 3.

[0057] As a preferred embodiment, the beam expander 4 includes a lens group and a microlens array, and is used to adjust the size and collimation of the beam to meet the incident conditions of the multi-plane optical converter 5.

[0058] As a preferred embodiment, the number of reflections of the multi-plane optical converter 5 is two or more, and the coherent beam combination and mode conversion of the beam are realized through the optical Fourier transform during the reflection process. The number of reflections of the multi-plane optical converter 5 can be two or more by adjusting the distance between the phase plate 51 and the mirror 52, so as to generate structured light beams of different wavelengths or different modes, so that the system can dynamically switch the mode type of the output structured light beam by adjusting the phase distribution parameters of the phase plate 51.

[0059] In this embodiment, it is considered to perform laser beam combining on input optical fibers of different types and arrangements. The structures of the phase plate 51 and the mirror 52 in the multi-plane optical converter 5 are designed to be parallel to each other, and the distance between the phase plate 51 and the mirror 52 is adjustable to generate structured light beams of different wavelengths or different modes, so that the system can dynamically switch the mode type of the output structured light beam by adjusting the phase distribution parameters of the phase plate 51; and the phase plate 51 is designed as a spatial light modulator or a fixed phase plate, and its surface phase distribution is programmable or fixed, so that a predetermined phase modulation can be effectively applied to the incident light beam, improving the expansibility and mode coupling efficiency of fiber beam combining.

[0060] Embodiment Three:

[0061] This embodiment is further described based on the input multi-core optical fiber 3 in Embodiment One, as follows:

[0062] As a preferred embodiment, refer to Figure 2 And Figure 3 , the number of cores of the input multi-core optical fiber 3 includes one or more combinations of four cores, six cores, eight cores or ten cores, and the number of input multi-core optical fibers 3 includes a single root or multiple roots arranged in parallel. Among them, Figure 2 (a) is four cores, Figure 2 (b) is six cores, Figure 2 (c) is eight cores, Figure 2 (d) is ten cores; Figure 3 (e) is a multi-core optical fiber with a single root, Figure 3 (f) is a multi-core optical fiber with two roots, Figure 3 (g) is a multi-core optical fiber with three roots; The above implementation schemes are only descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention.

[0063] As a preferred embodiment, the light beams output from each core in the input multi-core optical fiber 3 are independently controlled by the phase polarization controller 2, so that the modes of the output structured light beam include but are not limited to LP01, LP11, LP21, LP31, OAM-1 or OAM-2 modes.

[0064] Specifically, in this embodiment, there is no need to perform special treatment on the fiber structure, and it does not rely on the beam combiner for mode selection. By adjusting the characteristics of the input laser, coherent beam combination can be achieved into mode light. The beam combination principle is:

[0065] Taking a single six-core optical fiber used in the experiment as an example in the present invention, as Figure 4 shown, the six cores in the six-core optical fiber are sequentially numbered 31, 32, 33, 34, 35, 36 in a clockwise direction. Referring to Table 1, when the light beams in the six-core optical fiber are in the same phase, after multi-plane optical conversion, they are coherently combined into LP01 mode light, asFigure 5 as shown

[0066] Table 1: LP01 mode light

[0067] Core Serial Number Phase 31 0 32 0 33 0 34 0 35 0 36 0

[0068] Refer to Table 2. When there is no light in the cores of 31 and 34, that is, the light intensity is zero, and at the same time, the light in the cores of 32 and 33 is in the same phase, the light in the cores of 35 and 36 is in the same phase, and the light in the cores of 32 and 35 is set with a phase difference of π, after multi-plane optical conversion, it is coherently combined into LP11 mode light, as Figure 6 shown

[0069] Table 2: LP11 mode light

[0070]

[0071]

[0072] Refer to Table 3. When there is no light in the cores of 31 and 34, that is, the light intensity is zero, and at the same time, the light in the cores of 32 and 35 is in the same phase, the light in the cores of 33 and 36 is in the same phase, and the light in the cores of 32 and 33 is set with a phase difference of π, after multi-plane optical conversion, it is coherently combined into LP21 mode light, as Figure 7 shown

[0073] Table 3: LP21 mode light

[0074] Core Serial Number Phase 31 - 32 0 33 π 34 - 35 0 36 π

[0075] Refer to Table 4. When the light in the cores of 31, 33, and 35 is in the same phase, the light in the cores of 32, 34, and 36 is in the same phase, and the light in the cores of 31 and 32 is set with a phase difference of π, after multi-plane optical conversion, it is coherently combined into LP31 mode light, as Figure 8 shown

[0076] Table 4: LP31 mode light

[0077] Core Serial Number Phase 31 0 32 π 33 0 34 π 35 0 36 π

[0078] Refer to Table 5. When the light in each core of the six-core optical fiber is applied with an equal-phase difference of π / 3 in the clockwise direction, after multi-plane optical conversion, it is coherently combined into OAM-1 mode light, as Figure 9 shown

[0079] Table 5: OAM-1 mode light

[0080] Core Serial Number Phase 31 0 32 π / 3 33 2π / 3 34 π 35 4π / 3 36 5π / 3

[0081] Referring to Table 6, when the light in each core of the six-core optical fiber is applied with an equal-phase difference of 2π / 3 in the clockwise direction, after multi-plane optical conversion, it is coherently combined into OAM-2 mode light, as Figure 10 shown.

[0082] Table 6: OAM-2 mode light

[0083]

[0084]

[0085] In this embodiment, the number of cores of the input multi-core optical fiber (3) is designed to be one or more combinations of four cores, six cores, eight cores or ten cores, and the number of input multi-core optical fibers (3) includes a single root or multiple roots arranged in parallel, capable of generating structured light beams with different transverse phases, polarizations and light field distributions.

[0086] The embodiments described above can further change parameters such as wavelength, the number of cores of the multi-core optical fiber, and the number of multi-core optical fibers. Moreover, the embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A multi-core fiber beam combining system based on multi-plane light conversion, characterized in that, The system includes: A laser light source (1), a phase polarization controller (2), an input multi-core optical fiber (3), a beam expander (4), and a multi-plane optical converter (5) arranged on the same parallel line; The light source output end of the laser light source (1) is connected to the input end of the phase polarization controller (2), the output end of the phase polarization controller (2) is connected to the input end of the input multi-core optical fiber (3), the output end of the input multi-core optical fiber (3) is connected to the input end of the beam expander (4), and the output end of the beam expander (4) is connected to the input end of the multi-plane optical converter (5); The phase polarization controller (2) is used to independently adjust the phase and polarization state of the light beam incident from the laser light source (1) to the input multi-core optical fiber (3) and output from each core of the input multi-core optical fiber (3); The beam expander (4) is used to amplify and collimate the light beam output from the input multi-core optical fiber (3); The multi-plane optical converter (5) is used to perform multiple phase transformations and optical Fourier transforms on the expanded and collimated light beam, and finally output a structured light beam with a specific intensity distribution, phase distribution, and polarization distribution.

2. The multi-core fiber beam combining system based on multi-plane optical conversion according to claim 1, wherein The multi-plane optical converter (5) includes a phase plate (51) and a mirror (52) arranged in parallel, and reflects the light beam multiple times through the parallel arrangement structure.

3. The multi-core fiber beam combining system based on multi-plane optical conversion according to claim 2, wherein, The phase plate (51) is a spatial light modulator or a fixed phase plate, and its surface phase distribution is programmable or fixed, and is used to apply a predetermined phase modulation to the incident light beam.

4. The multi-core fiber beam combining system based on multi-plane optical conversion according to claim 2, wherein The distance between the phase plate (51) and the mirror (52) is adjustable to generate structured light beams of different wavelengths or different modes.

5. The multi-core fiber beam combining system based on multi-plane light conversion according to claim 2, wherein The system dynamically switches the mode type of the output structured light beam by adjusting the phase distribution parameters of the phase plate (51).

6. The multi-core fiber beam combining system based on multi-plane optical conversion according to claim 1, wherein The beam expander (4) includes a lens group and a microlens array, and is used to adjust the size and collimation of the light beam to meet the incident conditions of the multi-plane optical converter (5).

7. The multi-core fiber beam combining system based on multi-plane optical conversion according to claim 1, characterized in that The number of reflections of the multi-plane optical converter (5) is two or more times, and the coherent beam combination and mode conversion of the light beam are realized through the optical Fourier transform during the reflection process.

8. The multi-core fiber beam combining system based on multi-plane optical conversion according to claim 1, characterized in that The number of cores of the input multi-core optical fiber (3) includes one or more combinations of four cores, six cores, eight cores, or ten cores, and the number of the input multi-core optical fibers (3) includes a single fiber or multiple fibers arranged in parallel.

9. The multi-core fiber beam combining system based on multi-plane optical conversion according to claim 1, characterized in that, The light beams output from each core of the input multi-core optical fiber (3) are independently controlled by the phase polarization controller (2), so that the modes of the output structured light beam include but are not limited to LP01, LP11, LP21, LP31, OAM-1, or OAM-2 modes.

10. The multi-core fiber beam combining system based on multi-plane optical conversion according to claim 1, characterized in that The transverse light field distribution, phase distribution, and polarization distribution of the structured light beam are jointly determined by the amplitudes, phase differences, and polarization states of the light beams of each core in the input multi-core optical fiber (3).

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