Optical fiber combiner and method of making same

Abstract

The application discloses an optical fiber combiner and a preparation method thereof, and relates to the technical field of optical fibers. The optical fiber combiner comprises multiple input optical fibers, an output optical fiber and a combiner medium. Multiple laser input channels and a laser output channel are arranged in the combiner medium. One end of the multiple laser input channels is merged to form a merging end. The multiple input optical fibers are correspondingly and perpendicularly fused with the incident ends of the multiple laser input channels. The output optical fiber is perpendicularly fused with the output end of the laser output channel. The preparation method comprises the following steps: forming the multiple laser input channels and the laser output channel by using a femtosecond laser to inscribe along a preset path in the combiner medium; correspondingly and perpendicularly fusing the multiple input optical fibers with the incident ends of the multiple laser input channels; and perpendicularly fusing the output optical fiber with the output end of the laser output channel. The application can effectively dissipate heat to reduce waveguide distortion caused by temperature changes, and improve stability.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber technology, and in particular to an optical fiber combiner and a preparation method thereof. Background Art

[0002] Fiber beam combining technology is the core means to achieve high-power laser output. Its development background mainly revolves around three major needs: power enhancement, beam quality optimization and system stability.

[0003] Existing fiber laser beam combining technologies mainly include spatial optical beam combining technology and fiber end-cap beam combining technology, but both have certain limitations. Among them, spatial optical beam combining uses free-space optical elements such as lenses, mirrors, and gratings to collimate and combine multiple laser beams. However, in this beam combining system, the optical elements are sensitive to factors such as vibration, dust, and temperature drift, requiring frequent calibration, poor stability, and large size. Fiber end-cap beam combining technology combines multiple beams directly after microstructure processing or coating on the fiber end face. The power density is concentrated at the end face, which can easily cause melting or coating carbonization.

[0004] In view of the problems existing in the above-mentioned prior art, those skilled in the art are in urgent need of a fiber combiner and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to provide an optical fiber combiner and a preparation method thereof to solve the problems existing in the above-mentioned prior art, which can effectively dissipate heat to reduce waveguide distortion caused by temperature changes and improve stability.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] In a first aspect, the present invention provides a fiber combiner comprising a plurality of input optical fibers, an output optical fiber, and a combining medium; a plurality of laser input channels and a laser output channel are provided inside the combining medium, one end of the plurality of laser input channels merges to form a combined end, and the combined end is connected to the input end of the output channel; an end of the laser input channel away from the laser output channel is an incident end, and the incident end extends to one side end face of the combining medium; an end of the laser output channel away from the laser input channel is an output end, and the output end extends to the other side end face of the combining medium; the plurality of input optical fibers correspond one-to-one to the incident ends of the plurality of laser input channels and are vertically fused, and the output optical fiber is vertically fused to the output end of the laser output channel.

[0008] In some embodiments, the laser input channel includes a straight section and an inclined section, the straight sections of multiple laser input channels are parallel to each other, one end of the straight section extends to one end of the beam combining medium to form the incident end, and the other end is connected to one end of the inclined section; the other ends of the inclined sections of multiple laser input channels are connected to form the converging end; the incident ends of multiple laser input channels are periodically arranged on one side end surface of the beam combining medium, and the mode field distribution space of multiple laser input channels at the converging end overlaps; the mode field distribution of the input end of the laser output channel matches the mode field distribution of the converging end of multiple laser input channels.

[0009] In some embodiments, the input channel and the output channel are formed by inscribing the interior of the beam combining medium using a femtosecond laser along a preset path, and both the input channel and the output channel are inscribed into a gradient refractive index structure using a femtosecond laser; the laser input channel and the laser output channel each include a fiber core and a cladding covering the fiber core, and the divergence angle θ of the laser input channel in the beam combining medium satisfies:

[0010] ;

[0011] Wherein, n1 is the refractive index of the core of the laser input channel, n2 is the refractive index of the cladding of the laser input channel, and n1>n2.

[0012] In some embodiments, a transition layer is provided on the side of the cladding close to the core, and the transition layer covers the core; the difference in refractive index between the core and the side of the cladding away from the core is 0.001-0.02, and the diameter of the core is 10~400μm; the refractive index of the transition layer is linearly distributed from the side close to the core to the side away from the core, and the thickness of the transition layer is 0~30μm; the cladding has a stress compensation area.

[0013] In some embodiments, the cores of the laser input channel and the laser output channel are both etched with a periodic grating structure, and the period of the grating structure is 0.5-2 μm.

[0014] In some embodiments, an isolation zone is formed between the multiple laser input channels by femtosecond laser writing, the width of the isolation zone is 0.1-0.5 times the core diameter, and the crosstalk suppression ratio is greater than 30dB; the multiple laser input channels are arranged at equal intervals in the same direction, and the spacing between the axes of two adjacent laser input channels is 1.2-1.5 times the core diameter; or the multiple laser input channels are arranged in a conical shape.

[0015] In some embodiments, the beam combining medium is a solid beam combining medium with a low thermal expansion coefficient, the thermal conductivity of the beam combining medium is greater than 20 W / (m•K), and the absorption loss of the beam combining medium in the 0.9-2.1 μm band is less than 0.01 dB / cm; and / or the beam combining medium is any one of quartz, sapphire, silicon crystal, rare earth doped YAG crystal or Al2O3-TiO2 composite ceramic.

[0016] In a second aspect, the present invention provides a method for preparing an optical fiber combiner, comprising the following steps: using a femtosecond laser to write along a preset path inside a combining medium to form a plurality of laser input channels and a laser output channel; corresponding a plurality of input optical fibers to the incident ends of the plurality of laser input channels one by one and fusing them vertically; fusing an output optical fiber vertically to the output end of the laser output channel; wherein one end of the plurality of laser input channels converges to form a converging end, the converging end is connected to the input end of the output channel, the incident end of the laser input channel extends to one side end face of the combining medium, and the output end of the laser output channel extends to the other side end face of the combining medium.

[0017] In some embodiments, the step of "using a femtosecond laser to write along a preset path inside the beam combining medium to form a plurality of laser input channels and laser output channels" includes: using a femtosecond laser with a pulse energy of 150-800fs and 10μJ-2mJ to write along a preset path inside the beam combining medium to form a pilot channel; using a femtosecond laser with a pulse energy of 20-100fs and 2μJ-100μJ to write on the basis of the pilot channel to form a plurality of the laser input channels and the laser output channels.

[0018] In some embodiments, the laser input channel and the laser output channel both include a fiber core and a cladding covering the fiber core, and the method further includes: using a femtosecond laser to write inside the beam combining medium along a preset fiber core path to change the refractive index and form the fiber core, and the portion of the beam combining medium covering the fiber core is the cladding; or using a femtosecond laser to write inside the beam combining medium along the periphery of the preset fiber core path to change the refractive index and form the cladding, and the portion covered by the cladding is the fiber core.

[0019] Compared with the prior art, the present invention has achieved the following technical effects:

[0020] The fiber optic combiner and preparation method of the present invention provide a laser input channel and a laser output channel in a combining medium, and a plurality of input optical fibers are vertically fused to the incident ends of the corresponding laser input channels, and the output optical fibers are vertically fused to the output ends of the laser output channels to achieve low-loss coupling; by providing the combining medium, heat can be effectively dissipated, waveguide distortion caused by temperature changes can be reduced, thermal lens effects can be avoided, and kilowatt-level to hundred-kilowatt-level laser combining can be supported; and the fiber optic combiner of the present invention has no free-space optical elements, reduces spatial optical path components, is resistant to vibration and dust, reduces the optical power loss of the laser during spatial transmission, and achieves high-efficiency, high-beam-quality, and high-stability laser combining, overcomes the inherent defects of traditional spatial combining systems, and improves stability.

[0021] Furthermore, the beam combining medium of the present invention is a solid beam combining medium with a low thermal expansion coefficient. The material of the beam combining medium has high thermal conductivity and low absorption loss, which can effectively dissipate heat, reduce energy loss, and improve laser transmission efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 Schematic diagram of the three-dimensional structure of the optical fiber combiner in some embodiments of the present invention;

[0024] Figure 2 is a cross-sectional view of a fiber combiner in some embodiments of the present invention;

[0025] Figure 3 This is one of the schematic diagrams of using a femtosecond laser to write in some embodiments of the present invention;

[0026] Figure 4 This is a second schematic diagram of writing using a femtosecond laser in some embodiments of the present invention;

[0027] Figure 5 This is one of the schematic diagrams of the arrangement of multiple laser input channels in some embodiments of the present invention;

[0028] Figure 6 This is a second schematic diagram of the arrangement of multiple laser input channels in some embodiments of the present invention;

[0029] Figure 7 Schematic diagram of using femtosecond laser to write and change the refractive index to form a fiber core in some embodiments of the present invention;

[0030] Figure 8 Schematic diagram of using femtosecond laser to write and change the refractive index to form a cladding in some embodiments of the present invention;

[0031] Figure 9 Schematic diagram of the structure of the pilot channel in some embodiments of the present invention;

[0032] Figure 10 Flowchart of main steps of a method for preparing an optical fiber combiner in some embodiments of the present invention.

[0033] In the figure: 1-input optical fiber; 2-output optical fiber; 3-beam combining medium; 4-laser input channel; 5-laser output channel; 6-femtosecond laser; 7-pilot channel; 11-fiber core; 12-cladding. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] The purpose of the present invention is to provide a fiber optic combiner and a preparation method thereof to solve the problems existing in the prior art, which can effectively dissipate heat and reduce waveguide distortion caused by temperature changes, and does not require the installation of free-space optical elements, thereby improving stability.

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] The embodiment of the present invention provides a fiber optic combiner, such as Figures 1 to 9 As shown, it includes two or more input optical fibers 1, an output optical fiber 2 and a beam combining medium 3; Figure 2 As shown, a plurality of laser input channels 4 and laser output channels 5 are provided inside the beam combining medium 3. One end of the plurality of laser input channels 4 is connected to form a combined end, and the other end of the laser input channel 4 is the incident end, which extends to one side of the end face of the beam combining medium 3. One end of the laser output channel 5 is the input end, which is connected and combined with the combined ends of the plurality of laser input channels 4. The other end of the laser output channel 5 is the output end, which extends to the other side of the end face of the beam combining medium 3. One end of the plurality of input optical fibers 1 corresponds one-to-one to the incident ends of the plurality of laser input channels 4 and is vertically fused. One end of the output optical fiber 2 corresponds to the output end of the laser output channel 5 and is vertically fused.

[0038] The lasers of multiple input optical fibers 1 of the present invention are converged through the laser input channel 4 and then pass through the laser output channel 5 and enter the output optical fiber 2 to achieve beam combining. The beam combining medium 3 can effectively dissipate heat, reduce waveguide distortion caused by temperature changes, avoid thermal lens effect, and support kilowatt- to hundred-kilowatt-level laser beam combining; and the present invention does not require the arrangement of free-space optical elements, reduces spatial optical path components, is resistant to vibration and dust, reduces the optical power loss of the laser during space transmission, and realizes high-efficiency, high-beam-quality, and high-stability laser beam combining, overcomes the inherent defects of traditional space beam combining systems, and improves stability.

[0039] It should be noted that those skilled in the art can specifically set the number of input optical fibers 1, and the present invention does not make any specific limitation; for example, multiple input optical fibers 1 are arranged in an M×N array, and M, N ≥ 2; and the number of laser input channels 4 is equal to the number of input optical fibers 1.

[0040] In some embodiments of the present invention, the multiple incident ends of the multiple laser input channels 4 located on one side end face of the beam combining medium 3 are periodically arranged, and the multiple laser input channels 4 have spatially overlapping mode field distributions at the confluence end, that is, the mode field distributions of the multiple laser input channels 4 at the confluence end spatially overlap, and power synthesis is achieved through incoherent superposition; and the input end of the laser output channel 5 and the confluence end of the laser input channel 4 form a mode field adaptation transition, that is, the mode field distribution of the input end of the laser output channel 5 matches the mode field distribution of the confluence end of the laser input channel 4, so that the transmitted laser loss is small and high beam quality transmission is maintained.

[0041] In some embodiments of the present invention, Figure 3 and Figure 4 As shown, the interior of the beam combining medium 3 is engraved with a femtosecond laser 6 according to a preset path to form a laser input channel 4 and a laser output channel 5, and both the laser input channel 4 and the laser output channel 5 are engraved with a femtosecond laser 6 to form a gradient refractive index structure, thereby achieving step-free mode field matching between the converging end of the laser input channel 4 and the laser output channel 5, thereby reducing mode field mismatch loss.

[0042] The laser input channel 4 and the laser output channel 5 both include a core 11 and a cladding 12, wherein the cladding 12 is used to cover the core 11, and the divergence angle θ of the laser input channel 4 in the beam combining medium 3 satisfies:

[0043] ;

[0044] Wherein, n1 is the refractive index of the core 11 of the laser input channel 4, n2 is the refractive index of the cladding 12 of the laser input channel 4, and the refractive index n1 of the core 11 is greater than the refractive index n2 of the cladding 12;

[0045] It should be noted that the refractive index of the core 11 and the refractive index of the cladding 12 of the present invention are related to the material and the preset value.

[0046] In some embodiments of the present invention, a transition layer is provided on the side of the cladding 12 close to the core 11, and the transition layer is used to cover the core 11; wherein, the refractive index difference between the core 11 and the refractive index of the cladding 12 away from the core 11 is △n=0.001-0.02, so as to achieve total reflection, constrain light beam transmission, and avoid energy leakage, and the diameter of the core 11 is 10~400μm; the refractive index of the transition layer is linearly distributed from the side close to the core 11 to the side away from the core 11, so that the refractive indices of the core 11, the transition layer and the remaining parts of the cladding 12 except the transition layer of the present invention form a gradient refractive index structure, and the thickness of the transition layer along the radial direction is 0~30μm.

[0047] It should be noted that those skilled in the art can set the thickness of the transition layer according to actual conditions to ensure step-free mode field matching between the confluence end of the laser input channel 4 and the laser output channel 5 and reduce mode field mismatch loss.

[0048] Furthermore, the cladding 12 has a stress compensation region, and the residual stress in the stress compensation region is less than 5 MPa.

[0049] In some embodiments of the present invention, a periodic grating structure is formed on the channel wall of the laser input channel 4 and the laser output channel 5. For example, a periodic grating structure is formed by etching at the core 11 of the laser input channel 4 and the laser output channel 5. The period of the grating structure is 0.5-2 μm, which is used to filter high-order modes, realize the transverse mode filtering function, improve the beam quality, and output the beam M. 2 The factors are close to single mode.

[0050] In some embodiments of the present invention, a femtosecond laser 6 is used to write a microstructure isolation zone between multiple laser input channels 4, including but not limited to an air hole array or a low refractive index doped region, with a width of 0.1-0.5 times the diameter of the fiber core 11, and a crosstalk suppression ratio of >30dB, ensuring the independence of the light beams during high-density beam combining. This embodiment improves the beam combining efficiency by optimizing the laser input channel density and reducing crosstalk.

[0051] In some embodiments of the present invention, Figure 5 As shown, the array of multiple laser input channels 4 can be a two-dimensional arrangement array. The two-dimensional arrangement refers to a densely packed structure in a plane, that is, multiple laser input channels 4 can be arranged at equal intervals along the same direction, and the spacing between the axes of two adjacent laser input channels 4 is 1.2 to 1.5 times the diameter of the fiber core 11.

[0052] like Figure 6As shown, the array of multiple laser input channels 4 can also be a three-dimensional arrangement array, specifically a three-dimensional conical arrangement, that is, the multiple laser input channels 4 have a common converging end and are arranged in a conical shape from the converging end, for example, they can be polygonal cones, circular cones, or elliptical cones, etc., and the present invention does not make specific limitations; Figure 6 As shown, the array arrangement of the laser input channels 4 is as follows: the incident ends of multiple laser input channels 4 are arranged in a circle on the periphery and the incident ends of several laser input channels 4 are located in the middle. At this time, the corresponding array arrangement of the multiple laser input channels 4 is a three-dimensional conical arrangement.

[0053] In some embodiments of the present invention, beam combining medium 3 is a solid-state medium with a low thermal expansion coefficient. This solid-state medium has a thermal conductivity greater than 20 W / (m·K), demonstrating excellent thermal conductivity. Its absorption loss in the 0.9-2.1 μm band is less than 0.01 dB / cm. This high thermal conductivity effectively dissipates heat, reduces waveguide distortion caused by temperature fluctuations, and avoids thermal lensing, enabling support for kilowatt- to 100-kilowatt laser beam combining. Its low absorption loss reduces energy loss and improves laser transmission efficiency.

[0054] The beam combining medium 3 of the present invention can be any one of quartz, sapphire, silicon crystal, rare earth element-doped YAG crystal or Al2O3-TiO2 composite ceramics; and the beam combining medium 3 can be a rectangular parallelepiped structure or other shapes; the present invention does not make specific restrictions on this.

[0055] The number of input optical fibers 1 and laser input channels 4 of the present invention can be 10 to 100, 100 to 200, or greater than 200. The fiber combiner provided in this embodiment has strong expansion capability, supports a larger number of fiber combiners, and eliminates the technical constraints of existing fiber combiners.

[0056] The embodiment of the present invention also provides a method for preparing a fiber optic combiner, which is used to prepare the above-mentioned fiber optic combiner. Figure 10 As shown, the following steps are included:

[0057] Step S1: using a femtosecond laser 6 to write along a preset path inside the beam combining medium 3 to form a plurality of laser input channels 4 and laser output channels 5;

[0058] Step S2: vertically splicing the multiple input optical fibers 1 to the incident ends of the multiple laser input channels 4 in a one-to-one correspondence;

[0059] Step S3: vertically fusing the output optical fiber 2 to the output end of the laser output channel 5;

[0060] Based on the above steps S1 to S3, it should be noted that one end of the multiple laser input channels 4 merges to form a merged end, which is connected to the input end of the laser output channel 5; the incident end of the laser input channel 4 extends to one end face of the beam combining medium 3, and the output end of the laser output channel 5 extends to the other end face of the beam combining medium 3.

[0061] The present invention uses a femtosecond laser to write a precise optical waveguide structure in a solid beam combining medium. It has no free-space optical elements, reduces the number of spatial optical path components, is resistant to vibration and dust, and reduces the optical power loss of the laser during spatial transmission. It achieves high-efficiency, high-beam-quality, and high-stability laser beam combining, overcomes the inherent defects of traditional spatial beam combining systems, and improves the stability of the laser system.

[0062] In some embodiments of the present invention, the above step S1 specifically includes:

[0063] Step S11: using a femtosecond laser 6 with a pulse energy of 150-800 fs and 10 μJ-2 mJ to write along a preset path inside the beam combining medium 3 to form a pilot channel 7;

[0064] Step S12: using a femtosecond laser 6 with a pulse energy of 20-100 fs and 2 μJ-100 μJ to write on the basis of the pilot channel 7 to form a plurality of laser input channels 4 and laser output channels 5 .

[0065] Based on the above steps S11 to S12, it should be noted that in step S12, refer to Figure 9 As shown, femtosecond laser 6 is used to write on the basis of the pilot channel 7. It should be understood that femtosecond laser 6 is used to write a fine-tuning channel on the pilot channel 7 to control the refractive index gradient. The laser writing accuracy used in the fine-tuning channel is higher, and the shape, change rate and other parameters of the regulated gradient refractive index are more accurate; the fine-tuning channel here includes a laser input channel 4 and a laser output channel 5; and the present invention forms a grating structure with a period of 0.5~2μm on the channel wall of the pilot channel 7 and / or the fine-tuning channel to realize the transverse mode filtering function.

[0066] In some embodiments of the present invention, the laser input channel 4 and the laser output channel 5 both include a core 11 and a cladding 12 covering the core 11. The preparation method of the present invention further includes:

[0067] Using a femtosecond laser 6 to write along a preset core path inside the beam combining medium 3 to change the refractive index and form a core 11, the portion of the beam combining medium 3 covering the core 11 is the cladding 12; or

[0068] The femtosecond laser 6 is used to write inside the beam combining medium 3 along the periphery of the preset core path to change the refractive index and form a cladding 12 , and the portion covered by the cladding 12 is the core 11 .

[0069] It should be noted that the emitting device of the femtosecond laser 6 of the present invention is connected to the three-dimensional moving device. Figure 3 In the embodiment, the femtosecond laser 6 can write the optical waveguide structure along the transverse direction of the beam combining medium 3, i.e., the horizontal axis direction. Figure 4 In the embodiment, the femtosecond laser 6 can also write the optical waveguide structure along the longitudinal direction of the beam combining medium 3, that is, the longitudinal axis direction.

[0070] like Figure 7 As shown, the femtosecond laser 6 can change the refractive index of the original solid beam combining medium along the preset core path, and the original solid beam combining medium outside the refractive index change range is equivalent to the cladding 12; Figure 8 As shown, the femtosecond laser 6 can also change the refractive index of the original solid beam combining medium along the periphery of the preset core to form a cladding 12, and finally make the refractive index of the core 11 and the cladding 12 different, so that the laser is transmitted along the core 11.

[0071] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A fiber combiner, characterized in that: It includes multiple input optical fibers, output optical fibers and a combining medium; A plurality of laser input channels and laser output channels are provided inside the beam combining medium, one end of the plurality of laser input channels merges to form a merged end, and the merged end is connected to the input end of the output channel; The end of the laser input channel away from the laser output channel is the incident end, and the incident end extends to one end surface of the beam combining medium; the end of the laser output channel away from the laser input channel is the output end, and the output end extends to the other end surface of the beam combining medium; The plurality of input optical fibers correspond one-to-one to the incident ends of the plurality of laser input channels and are vertically fused, and the output optical fibers are vertically fused to the output ends of the laser output channels; The laser input channel includes a straight section and an inclined section. The straight sections of the plurality of laser input channels are parallel to each other. One end of the straight section extends to one end of the beam combining medium to form the incident end, and the other end is connected to one end of the inclined section. The other ends of the inclined sections of the plurality of laser input channels are connected to form the converging end. The incident ends of the plurality of laser input channels are periodically arranged on one end surface of the beam combining medium, and the mode field distribution spaces of the plurality of laser input channels at the converging end overlap; The mode field distribution of the input end of the laser output channel matches the mode field distribution of the confluence ends of the plurality of laser input channels; The input channel and the output channel are formed by writing the beam combining medium in a preset path using a femtosecond laser, and both the input channel and the output channel are written into a gradient refractive index structure using a femtosecond laser.

2. The optical fiber combiner according to claim 1, wherein: The laser input channel and the laser output channel both include a fiber core and a cladding covering the fiber core, and the divergence angle θ of the laser input channel in the beam combining medium satisfies: ； Wherein, n1 is the refractive index of the core of the laser input channel, n2 is the refractive index of the cladding of the laser input channel, and n1>n2.

3. The optical fiber combiner according to claim 2, wherein: A transition layer is provided on a side of the cladding close to the fiber core, and the transition layer covers the fiber core; The difference in refractive index between the core and the cladding on the side away from the core is 0.001-0.02, and the diameter of the core is 10~400μm; the refractive index of the transition layer is linearly distributed from the side close to the core to the side away from the core, and the thickness of the transition layer is 0~30μm; the cladding has a stress compensation area.

4. The optical fiber combiner according to claim 2, wherein: The fiber cores of the laser input channel and the laser output channel are both etched with a periodic grating structure, and the period of the grating structure is 0.5-2 μm.

5. The optical fiber combiner according to claim 1, wherein: An isolation zone is formed between the plurality of laser input channels by femtosecond laser writing. The width of the isolation zone is 0.1-0.5 times the diameter of the fiber core, and the crosstalk suppression ratio is greater than 30dB. The multiple laser input channels are arranged at equal intervals along the same direction, and the distance between the axes of two adjacent laser input channels is 1.2 to 1.5 times the diameter of the fiber core; or the multiple laser input channels are arranged in a cone shape.

6. The optical fiber combiner according to claim 1, wherein: The beam combining medium is a solid beam combining medium with a low thermal expansion coefficient, the thermal conductivity of the beam combining medium is greater than 20 W / (m•K), and the absorption loss of the beam combining medium in the 0.9-2.1 μm band is less than 0.01 dB / cm; and / or The beam combining medium is any one of quartz, sapphire, silicon crystal, YAG crystal doped with rare earth elements or Al2O3-TiO2 composite ceramics.

7. A method for preparing an optical fiber combiner, characterized in that: The following steps are involved: Using a femtosecond laser to write along a preset path inside the beam combining medium to form multiple laser input channels and laser output channels; The plurality of input optical fibers are matched one to one with the incident ends of the plurality of laser input channels and are vertically fused; Vertically fusing the output optical fiber to the output end of the laser output channel; One ends of the multiple laser input channels merge to form a merged end, which is connected to the input end of the output channel. The incident end of the laser input channel extends to one end surface of the beam combining medium, and the output end of the laser output channel extends to the other end surface of the beam combining medium. The laser input channel includes a straight section and an inclined section. The straight sections of the multiple laser input channels are parallel to each other. One end of the straight section extends to one end of the beam combining medium to form the incident end, and the other end is connected to one end of the inclined section. The other ends of the inclined sections of the multiple laser input channels are connected to form the merged end. The incident ends of the multiple laser input channels are periodically arranged on one side end face of the beam combining medium, and the mode field distribution space of the multiple laser input channels at the confluence end overlaps; the mode field distribution of the input end of the laser output channel matches the mode field distribution of the confluence end of the multiple laser input channels; the input channel and the output channel are formed by engraving the interior of the beam combining medium according to a preset path using a femtosecond laser, and both the input channel and the output channel are engraved into a gradient refractive index structure using a femtosecond laser.

8. The method for preparing a fiber combiner according to claim 7, wherein: The step of "using a femtosecond laser to write along a preset path inside a beam combining medium to form a plurality of laser input channels and laser output channels" includes: A femtosecond laser with a pulse energy of 150-800 fs and 10 μJ-2 mJ is used to write along a preset path inside the beam combining medium to form a pilot channel; A femtosecond laser with a pulse energy of 20-100 fs and 2 μJ-100 μJ is used to write on the basis of the pilot channel to form a plurality of laser input channels and the laser output channels.

9. The method for preparing a fiber combiner according to claim 7, wherein: The laser input channel and the laser output channel both include a fiber core and a cladding covering the fiber core, and the method further includes: Using a femtosecond laser to write along a preset core path inside the beam combining medium to change the refractive index and form the core, the portion of the beam combining medium covering the core being the cladding; or A femtosecond laser is used to write inside the beam combining medium along the periphery of the preset core path to change the refractive index and form the cladding, and the portion covered by the cladding serves as the core.

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