Multi-core all-solid-state anti-resonance optical fiber and multi-wavelength optical fiber laser system

Abstract

The invention discloses a multi-core all-solid-state anti-resonance optical fiber and a multi-wavelength optical fiber laser system. The multi-core all-solid-state anti-resonance optical fiber comprises an inner cladding area, at least two fiber core structures arranged in the inner cladding area and an outer cladding area or a coating layer area arranged on the periphery of the inner cladding area. Each fiber core structure comprises a fiber core area and an anti-resonance area, the anti-resonance area is composed of at least one capillary tube group, each capillary tube group comprises a plurality of capillary tubes, and the capillary tubes in each capillary tube group are annularly arranged on the periphery of the fiber core area by taking the fiber core area as the center; the optical fiber matrixes filled in the capillaries in the anti-resonance area are the same, and the refractive index of the anti-resonance area is n3gt; the refractive index n2 of the inner cladding region is equal to the refractive index n1gt of the fiber core region; and the refractive index of the outer cladding region or the coating layer region is n4. The optical fiber provided by the invention is beneficial to high-density integration of a fiber core structure in a multi-core optical fiber, has a large mode field area and a high-order mode rejection ratio, and gives consideration to both high power and high light beam quality.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of fiber laser, in particular to a multi-core all-solid anti-resonant fiber and a multi-wavelength fiber laser system. Background Art

[0002] Benefiting from high efficiency, high beam quality and excellent heat dissipation performance, fiber laser technology has shined in the past 20 years, and all indicators of lasers have been comprehensively improved. At the same time, the fiber itself has the characteristics of high stability, high environmental adaptability and easy integration, and this advantage makes it widely used in many fields. Nevertheless, it is a generally recognized fact in the industry that factors such as fiber nonlinear effects and mode instability restrict the further improvement of the power of fiber laser systems. With the continuous in-depth research, many targeted suppression means have been proposed, which have achieved the effect of increasing the starting threshold to a certain extent, but have not fundamentally solved the problem. For example, single-core fiber lasers (including total reflection mechanism and anti-resonant mechanism), due to the fiber nonlinear effects at extreme powers, limit the power improvement; the research on multi-core fibers and lasers based on the total reflection light guiding mechanism mainly focuses on the 1μm band, and the research on multi-core fibers also includes the communication band. Such multi-core fibers used in the visible light band face the same problems as single-core fibers used in the visible light band, and it is difficult to balance a large mode field and high beam quality. In order to maintain high beam quality, the cores and numerical apertures (NA) of multi-core fibers need to be small, and such a small mode field area also limits the power level. In addition, multi-wavelength, high-power laser systems based on optical path beam combining are complex and costly, and at the same time, the control efficiency and synthesis efficiency restrict the scalability of the solution.

[0003] The emergence of multi-core fiber lasers provides a feasible solution for the power improvement of fiber laser systems. In recent years, the research on multi-core fiber lasers based on the total reflection light guiding mechanism has become a hot topic. The research on high-power and high-brightness lasers mainly focuses on the 1μm band, and there is little research on the visible light band and mid-infrared. This is mainly because the phonon energy of common quartz-based fibers is high and not suitable for visible light and mid-infrared lasing. At the same time, the transmission loss of quartz-based fibers in the mid-infrared band is high.

[0004] In addition, the emergence of multi-core fibers provides a new technical route for multi-wavelength lasers. Previously, the technical routes for multi-wavelength lasers included multi-wavelength semiconductor lasers, multi-wavelength lasers based on nonlinear effects (fibers, solids), and multi-wavelength lasers based on optical path beam combining. However, the above lasers have more or less deficiencies such as complex systems, high costs, limited wavelength numbers and wavelength selections. The multi-core fiber laser with one fiber and multiple cores not only enriches the wavelength numbers and wavelength selection diversity of multi-wavelength lasers, but also greatly simplifies the system complexity and improves the system stability. However, multi-core fiber lasers based on the total reflection mechanism cannot balance the advantages of a large mode field and high beam quality.

[0005] It is widely believed in the art that if the spacing between the core structures of a multi-core optical fiber is too small, mode coupling is likely to occur and crosstalk increases. In order to obtain weak coupling, the spacing between the core structures needs to be increased, which is not conducive to the high-density integration of the core structures in the multi-core optical fiber. For example, in the patent application with the publication number CN 117613647 A, it is mentioned that a multi-core optical fiber based on the total internal reflection light guiding mechanism needs to meet the requirement that the minimum center spacing between any adjacent rare earth-doped cores should be no less than 2.5 times the diameter of the rare earth-doped core. Summary of the Invention

[0006] Aiming at the technical problems existing in the prior art, the present invention proposes a multi-core all-solid anti-resonant optical fiber and a multi-wavelength fiber laser system, which can effectively avoid the problem that in current multi-core optical fibers, in order to obtain weak coupling, the spacing between the core structures needs to be increased, which is not conducive to the high-density integration of the core structures in the multi-core optical fiber. The multi-core all-solid anti-resonant optical fiber proposed by the present invention is conducive to the high-density integration of the core structures in the multi-core optical fiber.

[0007] To achieve the above object, the technical solutions adopted by the present invention are as follows: On the one hand, a multi-core all-solid anti-resonant optical fiber is provided, which includes an inner cladding region, at least two core structures arranged inside the inner cladding region, and an outer cladding region or a coating layer region arranged outside the inner cladding region; each core structure includes a core region and an anti-resonant region, the anti-resonant region is composed of at least one capillary group, each capillary group includes a plurality of capillaries, the capillaries in each capillary group are annularly arranged around the core region with the core region as the center, the optical fiber matrices filled in the capillaries in the anti-resonant region are the same, and the refractive index n3 of the anti-resonant region > the refractive index n2 of the inner cladding region = the refractive index n1 of the core region > the refractive index n4 of the outer cladding region or the coating layer region; The structures and parameters of different core structures are the same as or different from each other, and each core structure is a centrosymmetric structure, and the center spacing between each core structure is not less than 1 times the diameter of the largest core structure.

[0008] Furthermore, the optical fiber matrix in the core region may be doped with rare earth ions or may not be doped with rare earth ions. Further, if the optical fiber matrix in the core region is doped with rare earth ions, the rare earth ions doped in the optical fiber matrix in the core region may be any one of ytterbium, erbium, thulium, neodymium, holmium, samarium, praseodymium, dysprosium, or the optical fiber matrix in the core region may be co-doped with two rare earth ions, such as erbium-ytterbium co-doping, praseodymium-ytterbium co-doping or thulium-dysprosium co-doping, or the optical fiber matrix in the core region is doped with three or more rare earth ions. Further, the types of rare earth ions doped in the optical fiber matrices of the core regions of each core structure are the same as or different from each other.

[0009] Furthermore, the shapes, dimensions, and wall thicknesses of the capillaries in the same capillary group within the same core structure are the same; the number of capillaries, the shapes, dimensions, and wall thicknesses of the capillaries between different capillary groups within the same core structure are the same as or different from each other; the number of capillary groups in different core structures, and the shapes, dimensions, and wall thicknesses of the capillaries in each capillary group are the same as or different from each other.

[0010] Furthermore, the anti-resonant region in each core structure includes a capillary group, each capillary group includes six capillaries, and the six capillaries are annularly arranged around the core region with the core region as the center, and the wall thicknesses of the capillaries are the same.

[0011] On the other hand, a multi-wavelength fiber laser system is provided, including the multi-core all-solid-state anti-resonant fiber described above.

[0012] Furthermore, the multi-wavelength fiber laser system includes a pump source, a high-reflection fiber grating, a gain fiber, a low-reflection fiber grating, and a cladding light filter. The gain fiber uses the multi-core all-solid-state anti-resonant fiber described above. Rare earth ions are doped in the fiber matrix of each core region of the multi-core all-solid-state anti-resonant fiber. The high-reflection fiber grating, the gain fiber, and the low-reflection fiber grating are connected in sequence. A resonant cavity is formed between the high-reflection fiber grating and the low-reflection fiber grating. The pump light output by the pump source is coupled into the resonant cavity through one end of the high-reflection fiber grating. The signal light output by the gain fiber is output through the low-reflection fiber grating and the cladding light filter. The pump wavelength of the pump source is within the resonant band of the gain fiber, and the signal wavelength is within the anti-resonant band of the gain fiber. And it is required that the high-order mode suppression ratio of the signal wavelength is greater than 100. Further, the pump source is a blue semiconductor laser. In the fiber matrix of the core region of each core structure in the gain fiber, a single rare earth ion, holmium or dysprosium, is doped respectively, that is, holmium ions are doped in the fiber matrix of the core region of a part of the core structures, and dysprosium ions are doped in the fiber matrix of the core region of a part of the core structures.

[0013] Furthermore, the multi-wavelength fiber laser system includes a multi-wavelength transmission fiber. The multi-wavelength transmission fiber uses the multi-core all-solid-state anti-resonant fiber described above. Rare earth ions are not doped in the fiber matrix of each core region of the multi-core all-solid-state anti-resonant fiber. The multi-wavelength transmission fiber is used for two or more different wavelengths of laser, and the two or more different wavelengths of laser are transmitted through different core regions respectively.

[0014] Furthermore, the fiber matrix used in all regions of the multi-core all-solid-state anti-resonant fiber, including the inner cladding region, the core region, and the anti-resonant region, is the same and is ZBLAN. The components of ZBLAN include ZrF4, BaF2, LaF4, AlF3, and NaF.

[0015] Compared with the prior art, the technical effects of the present invention are: The multi-core all-solid-state anti-resonant optical fiber proposed in the present invention has at least two core structures arranged inside the inner cladding region, each core structure including a core region and an anti-resonant region, and such a structural design can well constrain the transmitted light beam in the core region of each core structure. Moreover, the spacing between the core structures of the multi-core all-solid-state anti-resonant optical fiber with such a structural design is not limited. If the current technological level is not considered, it is found by simulating the multi-core all-solid-state anti-resonant optical fiber with this structure that even if the core structures overlap with each other, the simulation results show that the transmitted light beam can also be well constrained in the core region of each core structure. Considering the current technological limitations of drawing optical fibers, the present invention sets each core structure not to overlap with each other, and the center spacing between each core structure is not less than 1 times the maximum core structure diameter, which is much lower than the requirement for the core spacing in the multi-core optical fiber in the prior art. For example, the patent application with the publication number CN 117613647 A mentions that the multi-core optical fiber based on the total reflection light guiding mechanism needs to meet the following requirements: the minimum center spacing between any adjacent rare earth-doped cores should be not less than 2.5 times the diameter of the rare earth-doped core. The multi-core all-solid-state anti-resonant optical fiber proposed by the present invention is more conducive to the high-density integration of the core structure in the multi-core optical fiber.

[0016] The multi-core all-solid-state anti-resonance optical fiber proposed by the present invention has the advantages of both high power and high beam quality.

[0017] The multi-wavelength fiber laser system of the present invention adopts a fiber structure, which has a small volume, a large volume-surface ratio, and a strong anti-interference ability, so it has the advantages of simple and compact structure, high stability, good heat dissipation, etc. In other technical solutions of multi-wavelength laser systems without fiber structures, the laser propagates in free space and is easily affected by the external environment, so it does not have the advantages of the present invention.

[0018] The present invention uses rare earth doped multi-core all-solid anti-resonant optical fiber as gain optical fiber and adopts anti-resonant light guiding mechanism. At the beginning of gain optical fiber design, a gain optical fiber with large mode field area and high high-order mode suppression ratio can be designed, so that the high-order mode is lost during the transmission process (usually the high-order mode suppression ratio is greater than 100 and can be considered as single-mode transmission), taking into account both high power and high beam quality. In multi-core optical fiber with total reflection light guiding mechanism, due to its own mechanism limitation, especially for short wavelength, the large mode field designed to achieve high power is inconsistent with the goal of high beam quality, so it does not have the advantages of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0020] Figure 1 Schematic cross-sectional view of a multi-core all-solid anti-resonant fiber in an embodiment; Figure 2 Schematic structural view of a multi-wavelength fiber laser system in an embodiment; Figure 3 Graph showing the variation of the refractive index of the core region and the anti-resonant region filling material of the designed gain fiber with wavelength in an embodiment; Figure 4 Graph of the single-mode transmission characteristics of the designed gain fiber in an embodiment, where Figure 4 (a) is the curve of the confinement loss of the fundamental modes (LP 01 ) at 543 nm and 575 nm varying with d1 / D when d2 / d1 = 0.5, Figure 4 (b) is the curve of the confinement loss of the fundamental mode (LP 01 ) and the higher-order modes (LP 11 ) at 543 nm and the higher-order mode suppression ratio (HOMER) varying with d2 / d1 when d1 / D = 0.74, Figure 4 (c) is the curve of the confinement loss of the fundamental mode (LP 01 ) and the higher-order modes (LP 11 ) at 575 nm and the higher-order mode suppression ratio (HOMER) varying with d2 / d1 when d1 / D = 0.71; Figure 5 Electric field distribution diagram of a six-core double-clad all-solid anti-resonant fiber without rare-earth ion doping obtained by simulation in an embodiment, where Figure 5 (a) is the electric field distribution diagram of LP 01 in each core region, Figure 5 (b) is the electric field distribution diagram of LP 11 ; Figure 6 LP 01 electric field distribution diagram and microstructure magnification diagram of a six-core double-clad all-solid anti-resonant fiber without rare-earth ion doping obtained by simulation in an embodiment, where Figure 6 (a) is the LP 01 electric field distribution diagram of the six-core double-clad all-solid anti-resonant fiber without rare-earth ion doping at 543 nm, Figure 6 (b) is the microstructure magnification diagram of the six-core double-clad all-solid anti-resonant fiber without rare-earth ion doping.

[0021] Numbers in the figure: 1 is the core region, 2 is the inner cladding region, 3 is the anti-resonance region, and 4 is the outer cladding region or the coating region; 10 is a pump source, 20 is a quartz pigtail from the pump source, 30 is a high-reflection fiber Bragg grating, 40 is a gain fiber, 50 is a low-reflection fiber Bragg grating, and 60 is a cladding light filter. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0023] Reference Figure 1 The multi-core all-solid-state anti-resonant optical fiber provided by the present invention comprises an inner cladding region 2, at least two core structures arranged inside the inner cladding region 2, and an outer cladding region or coating region 4 arranged outside the inner cladding region; Each core structure includes a core region 1 and an antiresonance region 3, wherein the antiresonance region 3 is composed of at least one capillary group, each capillary group includes a plurality of capillaries, and the capillaries in each capillary group are arranged in a ring around the core region with the core region as the center, and the optical fiber matrix filled in each capillary in the antiresonance region 3 is the same, and the refractive index n3 of the antiresonance region 3>the refractive index n2 of the inner cladding region 2=the refractive index n1 of the core region 1>the refractive index n4 of the outer cladding region or the coating region.

[0024] Furthermore, the multi-core all-solid-state anti-resonant optical fiber may also include an outer cladding region or coating region 4 arranged outside the inner cladding region 2. There are at least two core structures inside the inner cladding region 2, which can be arranged in any shape, usually in a circular array. From the perspective of actual optical fiber drawing and application, it is necessary to constrain the core structures not to overlap, that is, the center spacing between the core structures is not less than 1 times the maximum core structure diameter.

[0025] In one embodiment, a multi-core all-solid anti-resonant optical fiber is provided, in which rare earth ions are doped in the optical fiber matrix of the core region 1. The multi-core all-solid anti-resonant optical fiber with rare earth ions doped in the optical fiber matrix of the core region 1 can be used as the gain fiber of a multi-wavelength fiber laser system. The rare earth ions can be any one of ytterbium, erbium, thulium, neodymium, holmium, samarium, praseodymium, dysprosium, etc., or two co-doped rare earth ions such as erbium-ytterbium, praseodymium-ytterbium, thulium-dysprosium, etc., or three or more rare earth ions can also be doped; the rare earth ions doped in the optical fiber matrix of the core regions of each core structure can be the same or different, and the doping situation can be designed according to actual needs specifically.

[0026] The multi-core all-solid anti-resonant optical fiber can select whether to dope rare earth ions and the specific doping method of rare earth ions according to requirements to achieve single-wavelength laser transmission or multi-wavelength laser transmission.

[0027] In one embodiment, a multi-core all-solid anti-resonant optical fiber is provided, in which no rare earth ions are doped in the optical fiber matrix of the core region 1, and it can be used as the multi-wavelength transmission fiber of a multi-wavelength fiber laser system.

[0028] In the multi-core all-solid anti-resonant optical fiber provided by the present invention, the anti-resonant region 3 of the core structure is composed of at least one capillary group, each capillary group is composed of at least four capillaries, and the capillary can be a single-tube structure or a nested-tube structure, and is arranged in a ring layout around the core region at equal intervals without nodes with the core region as the center. Each capillary in the capillary group has a certain wall thickness. The sizes and wall thicknesses of the capillaries included in the capillary group in the same core structure are usually the same. The diameters and wall thicknesses of the capillaries included in the capillary group in different core structures can be different.

[0029] Regarding the refractive index magnitude relationship of the filling materials (i.e., optical fiber matrix) in all regions of the multi-core all-solid anti-resonant optical fiber: the refractive index n3 of the anti-resonant region 3 > the refractive index n2 of the inner cladding region 2 = the refractive index n1 of the core region 1 > the refractive index n4 of the outer cladding region or the coating region 4. It should be noted that the filling materials in the internal region of the capillary and the filling materials in the inner cladding region can be the same or different.

[0030] In a preferred embodiment, the optical fiber matrices used in all regions of the multi-core all-solid anti-resonant optical fiber, including the inner cladding region 2, the core region 1, and the anti-resonant region 3, are the same and are all ZBLAN. The components of ZBLAN include ZrF4, BaF2, LaF4, AlF3, and NaF. The optical fiber matrices used in all regions of the multi-core all-solid anti-resonant optical fiber, including the inner cladding region 2, the core region 1, and the anti-resonant region 3, are the same. In addition to ZBLAN, other optical fiber matrices with lower phonon energy and capable of realizing visible light lasing, such as fluoroaluminum-based and fluoroindium-based, can also be used.

[0031] The number of core structures, the number of cladding structures (double cladding, triple cladding, etc.), the arrangement of the cores, etc. in the present invention are not limited, and those skilled in the art can reasonably select and adjust the design according to the needs. In addition, the shape of the core region is not limited, and can be D-shaped, double D-shaped, regular polygonal, etc.

[0032] Reference Figure 1 , a schematic cross-sectional view of a multi-core all-solid-state anti-resonant optical fiber in an embodiment, which has six core structures and adopts a double cladding structure. Each core structure includes a capillary group, each capillary group includes six capillaries, and each capillary is a nested tube structure, including an outer tube and an inner tube inside the outer tube. The capillaries in each core structure have the same wall thickness and different diameters. The design of the capillary wall thickness t in each core structure should follow the anti-resonance theory, that is, ( n 3 and n 1 is the refractive index of the antiresonance region and the core region, m is a positive integer), is the resonant wavelength. The light at the resonant wavelength or in the resonant band cannot be transmitted in the core area and will leak into the cladding. The resonant band range is defined by multiple parameters. Therefore, when designing a multi-core all-solid-state anti-resonant fiber, the pump wavelength is required to be in the resonant band, the signal wavelength is required to be in the anti-resonant band, and the high-order mode suppression ratio (HOMER) of the signal wavelength is required to be no less than 100. HOMER is the high-order mode with the lowest loss (LP 11 mode) and the limiting loss value of the core fundamental mode (LP 01 mode) limit the ratio of the loss values, that is: When the HOMER value is greater than 100, the optical fiber is considered to maintain single-mode transmission.

[0033] Another embodiment provides a multi-wavelength fiber laser system, using the multi-core all-solid-state anti-resonance fiber proposed in any of the above embodiments as a gain fiber, wherein the fiber matrix of each core region of the multi-core all-solid-state anti-resonance fiber is doped with rare earth ions. Figure 2 The multi-wavelength fiber laser system includes a pump source 10, a quartz pigtail 20 from the pump source, a high-reflection fiber grating 30, a gain fiber 40, a low-reflection fiber grating 50, and a cladding light filter 60. The gain fiber 40 adopts the multi-core all-solid-state anti-resonance fiber proposed in any of the above embodiments, and the fiber matrix of each core region of the multi-core all-solid-state anti-resonance fiber is doped with rare earth ions, which can realize a high-power, high-beam-quality multi-wavelength fiber laser. The multi-wavelength fiber laser system adopts an optical fiber structure, and the optical fiber has a small volume, a large volume-surface ratio, and a strong anti-interference ability, so it has the advantages of simple and compact structure, high stability, and good heat dissipation.

[0034] The pump source is equipped with a quartz pigtail 20 at its own end, which is connected to one end of the high-reflection fiber grating 30. The other end of the high-reflection fiber grating 30 is connected to one end of the gain fiber 40. The other end of the gain fiber 40 is connected to one end of the low-reflection fiber grating 50. The other end of the low-reflection fiber grating 50 is connected to one end of the cladding light filter 60, and the other end of the cladding light filter 60 outputs to free space.

[0035] The pump light output by the pump source 10 passes through the quartz pigtail 20 of the pump source itself and the high-reflection fiber grating 30, and then enters the resonant cavity formed between the high-reflection fiber grating 30 and the low-reflection fiber grating 50, and is absorbed by the gain fiber 40. At a certain pump light power, signal light lasers of multiple wavelengths are emitted, and pass through the low-reflection fiber grating 50 and the cladding light filter 60 and output to space. The pump wavelength of the pump source 10 is within the resonant band of the gain fiber 40, and the signal wavelength is within the anti-resonant band of the gain fiber 40, and it is required that the high-order mode suppression ratio of the signal wavelength is greater than 100.

[0036] The fibers used for engraving the high-reflection fiber grating 30 and the low-reflection fiber grating 50 are both the gain fiber 40. The high-reflection fiber grating 30 and the low-reflection fiber grating 50 can be directly engraved on the gain fiber 40. The high-reflection fiber grating 30 is used for wavelength selection and providing higher feedback, and the high-reflection fiber grating corresponding to the output wavelength is engraved inside each core region of the gain fiber 40. The low-reflection fiber grating is used for providing a certain degree of feedback and outputting signal light lasers, and the low-reflection fiber grating corresponding to the output wavelength is engraved inside each core region of the gain fiber 40. In this way, an all-fiber structure laser is built to make the system operate more stably and improve the system stability and robustness.

[0037] The center of the reflection band of the high-reflection fiber grating 30 is at the target lasing wavelength of the doped rare-earth ions in the corresponding core region, the reflection bandwidth is ~3nm, and the reflectivity is ~99%.

[0038] Further, the center of the reflection band of the low-reflection fiber grating is at the target lasing wavelength of the doped rare-earth ions in the corresponding core region, the reflection bandwidth is ~1nm, and the reflectivity ranges from 4% to 80%.

[0039] Further, the fiber used to prepare the cladding light filter 60 is the same as the gain fiber 40.

[0040] In one embodiment, based on Figure 2 the structure shown, a multi-wavelength fiber laser system is provided, specifically a dual-wavelength fiber laser system. In this embodiment, the pump source 10 is a blue semiconductor laser, which is used to generate pump laser for visible light laser. The gain fiber 40 is a six-core double-clad all-solid anti-resonant fiber doped with rare-earth ions, and its cross-sectional schematic diagram is as Figure 1As shown, the rare earth ions doped in the optical fiber matrix in the core region of the gain optical fiber 40 can be holmium and dysprosium. Among them, the optical fiber matrix in the core region of the three core structures is doped with holmium ions, and the optical fiber matrix in the core region of the other three core structures is doped with dysprosium ions. Both types of rare earth ions can use the above pump source as pump laser. The holmium ions can emit laser at 543 nm, and the dysprosium ions can emit laser at 575 nm. A high-reflection fiber grating 30 and a low-reflection fiber grating 50 are directly written on the gain optical fiber 40. The cladding light filter 60 is used to filter out the residual pump light and the high-order mode signal light in the cladding.

[0041] In this embodiment, the rare earth ions doped in the optical fiber matrix in the core region of the gain optical fiber 40 are holmium ions and dysprosium ions. The holmium ions can emit laser at 543 nm, and the dysprosium ions can emit laser at 575 nm. This embodiment designs a double-clad all-solid anti-resonant optical fiber with a six-core double-nested structure that supports dual wavelengths, high beam quality, and high-power transmission. Among them, the optical fiber matrix in the core region of the three core structures is doped with holmium ions, and the optical fiber matrix in the core region of the other three core structures is doped with dysprosium ions. Its structure is as Figure 1 shown. All regions of the gain optical fiber 40, including the inner cladding region, the core region, and the anti-resonant region, use the same optical fiber matrix, which is ZBLAN (ZrF4-BaF2-LaF4-AlF3-NaF). The components of ZBLAN include ZrF4, BaF2, LaF4, AlF3, and NaF.

[0042] Furthermore, the filling material for all regions of the gain optical fiber is ZBLAN (ZrF4-BaF2-LaF4-AlF3-NaF). The component ratios in different regions are different. By adjusting the component ratios, the refractive index required for each region is adjusted. The specific refractive index change of the filling material used in this embodiment with wavelength is as Figure 3 shown. The refractive index of the selected filling material is the common refractive index of existing commercial step-index fluoride optical fibers, which is easy to draw. The double-clad all-solid anti-resonant optical fiber (doped with holmium ions and dysprosium ions), its structure is as Figure 1As shown, in terms of specific parameters, the core region diameter D is 20 μm; the inner cladding region diameter is 125 μm; the outer cladding region diameter is 250 μm; the outer tube diameter of the double-nested capillary in the anti-resonant region is d1, and the inner tube diameter is d2; for the core structure with a transmission wavelength of 543 nm, the preferred value of the outer tube diameter d1 of the double-nested capillary in the anti-resonant region is 14.8 μm, and the preferred value of the inner tube diameter d2 is 7.4 μm. For the core structure with a transmission wavelength of 575 nm, the preferred value of the outer tube diameter d1 of the double-nested capillary in the anti-resonant region is 14.2 μm, and the preferred value of the inner tube diameter d2 is 8.662 μm; the capillary wall thickness t is 1.5 μm in all cases. The capillary wall thickness affects the transmission loss of the optical fiber, further affecting the power level of the output laser and the efficiency of the fiber laser.

[0043] The optimization process of the preferred value of the gain fiber is as Figure 4 shown, where Figure 4 (a) is the curve of the confinement loss of the fundamental mode (LP 01 ) at 543 nm and 575 nm varying with d1 / D when d2 / d1 = 0.5. The value of d1 / D corresponding to the minimum confinement loss value of the wavelength fundamental mode (LP 01 ) is taken as the preferred value of d1 / D (0.74@543 nm, 0.71@575 nm in this embodiment), and then the preferred value of d1 is determined (14.8 μm@543 nm, 14.2 μm@575 nm in this embodiment). As seen from Figure 4 (a), the value of d1 / D does not change regularly with the confinement loss value of the fundamental mode (LP 01 ), and the preferred value can only be obtained through optimization design. Figure 4 (b) is the curve of the confinement loss of the fundamental mode (LP 01 ), higher-order modes (LP 11 ) and the higher-order mode suppression ratio (HOMER) varying with d2 / d1 at 543 nm when d1 / D = 0.74. The value of d2 / d1 corresponding to the smaller confinement loss of the fundamental mode (LP 01 ) and a higher-order mode suppression ratio (HOMER) value greater than 100 is taken as the preferred value of d2 / d1 (0.5 in this embodiment), and then the preferred value of d2 is determined (7.4 μm in this embodiment). Figure 4 (c) is the curve of the confinement loss of the fundamental mode (LP 01 ), higher-order modes (LP 11 ) and the higher-order mode suppression ratio (HOMER) varying with d2 / d1 at 575 nm when d1 / D = 0.71. The value of d2 / d1 corresponding to the smaller confinement loss of the fundamental mode (LP 01The value of d2 / d1 corresponding to a relatively small confinement loss and a high-order mode suppression ratio (HOMER) value greater than 100 is the preferred value of d2 / d1 (0.61 in this embodiment), and then the preferred value of d2 is determined (8.662 μm in this embodiment).

[0044] In one embodiment, a multi-wavelength fiber laser system is provided, including a multi-core all-solid anti-resonant fiber. No rare-earth ions are doped in the fiber matrix of each core region of the multi-core all-solid anti-resonant fiber. The multi-wavelength transmission fiber is used for lasers of two or more different wavelengths, and the lasers of two or more different wavelengths are respectively transmitted through different core regions. In a specific embodiment, as Figure 5 shown Figure 5 is the electric field distribution diagram of a six-core double-clad all-solid anti-resonant fiber without rare-earth ion doping obtained by simulation in one embodiment, where Figure 5 (a) is the electric field distribution diagram of LP 01 in each core region, Figure 5 (b) is the electric field distribution diagram of LP 11 Figure 5 For the six-core double-clad all-solid anti-resonant fiber without rare-earth ion doping in Figure 1 , its structure is exactly the same as the structure and the setting of the structure parameters of the embodiment shown in Figure 5 . The center distance between each core structure is 1.5 times the core structure diameter. The difference is only that no rare-earth ions are doped in each core region. Among them, three core regions are used to transmit 575 nm, and the other three core regions are used to transmit 543 nm. It can be seen from Figure 5 (a) that the fundamental mode energy is well confined in each core, and there is no obvious energy distribution in the non-core region, that is, the confinement loss is relatively small. 11 (b) is the electric field distribution diagram of LP Figure 5 (a) shown in 01 . It forms an obvious contrast with the electric field distribution diagram of LP 11 in the core. The LP

[0045] As Figure 6 shown Figure 6 is the electric field distribution diagram and the microstructure magnification diagram of LP 01 of a six-core double-clad all-solid anti-resonant fiber without rare-earth ion doping obtained by simulation in one embodiment. The difference between the core structure parameters of Figure 5 and the six-core double-clad all-solid anti-resonant fiber without rare-earth ion doping in the embodiment shown in Figure 6 is that the center distance between each core structure in Figure 6 ​(a) shows the LP 01 electric field distribution diagram of a six-core double-clad all-solid anti-resonant fiber without rare-earth ion doping at 543 nm. It can be seen that the LP 01 mode can still be well confined in their respective core regions. Figure 6 (b) shows the enlarged microstructure diagram of a six-core double-clad all-solid anti-resonant fiber without rare-earth ion doping. It can be seen that although the core structures overlap severely, the LP 01 mode can still be well confined in their respective core regions.

[0046] In summary, for the multi-core all-solid anti-resonant fiber proposed by the present invention, if the current process level is not considered, the multi-core all-solid anti-resonant fiber designed with this structure is not limited by the spacing of the core structures. Even if the core structures overlap with each other, the simulation results show that the transmitted light beam can still be well confined in the core regions of each core structure. Considering the current process limitations of drawing fibers, the present invention arranges that the core structures do not overlap with each other. The multi-core all-solid anti-resonant fiber proposed by the present invention is more conducive to the high-density integration of the core structures in the multi-core fiber.

[0047] Matters not covered in the present invention are well-known technologies.

[0048] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0049] The above-described embodiments merely represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

[0050] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and variations. For example, gain fibers with other structural parameters can be designed, doping ions can be changed, and the pump light wavelength can be changed to achieve laser output of other signal wavelengths. For example, by using a 0.8 μm laser pump and doping neodymium ions, 1 μm and 1.3 μm laser outputs can be achieved; by using a 1.1 μm laser pump and doping holmium ions, 1.2 μm and 2 μm laser outputs can be achieved; by using a 793 nm laser pump and doping erbium ions, 2.7 μm laser output can be achieved; by using a 980 nm laser pump and doping erbium ions, 1.55 μm laser output can be achieved, etc. The above have all been verified in step-index fibers. It should be noted that different pump wavelengths may be required when doping ions in the fiber emit different lasers, and the present invention can also meet the requirements, as long as all pump laser wavelengths are designed within the resonance band during fiber design. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Multi-core all-solid anti-resonant optical fiber, characterized in that, It includes an inner cladding region, at least two core structures disposed inside the inner cladding region, and an outer cladding region or a coating region disposed around the inner cladding region; Each core structure includes a core region and an anti-resonant region. The anti-resonant region is composed of at least one capillary group. Each capillary group includes a plurality of capillaries. The capillaries in each capillary group are annularly arranged around the core region with the core region as the center. The optical fiber matrices filled in the capillaries in the anti-resonant region are the same. The refractive index n3 of the anti-resonant region > the refractive index n2 of the inner cladding region = the refractive index n1 of the core region > the refractive index n4 of the outer cladding region or the coating region; The structures and parameters of different core structures are the same as or different from each other, and each core structure has a centrosymmetric structure. The center-to-center distance between each core structure is not less than 1 times the maximum core structure diameter.

2. The multi-core all-solid anti-resonant optical fiber according to claim 1, wherein The optical fiber matrix in the core region is doped with rare earth ions.

3. The multi-core all-solid anti-resonant optical fiber according to claim 2, wherein The rare earth ions doped in the optical fiber matrix in the core region are any one of ytterbium, erbium, thulium, neodymium, holmium, samarium, praseodymium, dysprosium, or two or more rare earth ions are co-doped in the optical fiber matrix in the core region; the types of rare earth ions doped in the optical fiber matrices in the core regions of each core structure are the same as or different from each other.

4. The multi-core all-solid anti-resonant optical fiber according to claim 1 or 2 or 3, characterized in that, The shapes, sizes, and wall thicknesses of the capillaries in the same capillary group in the same core structure are the same; the number of capillaries, the shapes, sizes, and wall thicknesses of the capillaries between different capillary groups in the same core structure are the same as or different from each other; The number of capillary groups in different core structures, the shapes, sizes, and wall thicknesses of the capillaries in each capillary group are the same as or different from each other.

5. Multi-wavelength fiber laser system, characterized in that, It includes the multi-core all-solid anti-resonant optical fiber as described in claim 1.

6. The multi-wavelength fiber laser system according to claim 5, wherein It includes a pump source, a high-reflection fiber grating, a gain fiber, a low-reflection fiber grating, and a cladding light filter. The gain fiber uses the multi-core all-solid anti-resonant optical fiber as described in claim 1. The optical fiber matrices in the core regions of the multi-core all-solid anti-resonant optical fiber are doped with rare earth ions. The high-reflection fiber grating, the gain fiber, and the low-reflection fiber grating are connected in sequence. A resonant cavity is formed between the high-reflection fiber grating and the low-reflection fiber grating. The pump light output by the pump source is coupled into the resonant cavity through one end of the high-reflection fiber grating. The signal light output by the gain fiber is output through the low-reflection fiber grating and the cladding light filter. The pump wavelength of the pump source is within the resonant band of the gain fiber, the signal wavelength is within the anti-resonant band of the gain fiber, and the high-order mode suppression ratio of the signal wavelength is required to be greater than 100.

7. The multi-wavelength fiber laser system according to claim 5, wherein It includes a multi-wavelength transmission optical fiber. The multi-wavelength transmission optical fiber uses the multi-core all-solid anti-resonant optical fiber as described in claim 1. The optical fiber matrices in the core regions of the multi-core all-solid anti-resonant optical fiber are not doped with rare earth ions. The multi-wavelength transmission optical fiber is used for two or more different wavelengths of lasers. The two or more different wavelengths of lasers are respectively transmitted through different core regions.

8. The multi-wavelength fiber laser system according to claim 6 or 7, characterized in that, All regions of the multi-core all-solid anti-resonant fiber, including the inner cladding region, the core region, and the anti-resonant region, use the same optical fiber matrix, which is ZBLAN. The components of ZBLAN include ZrF4, BaF2, LaF4, AlF3, and NaF.

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