Multi-core all-solid-state antiresonant fiber and multi-wavelength fiber laser system

Abstract

A multi-core, all-solid-state antiresonant optical fiber and a multi-wavelength optical fiber laser system are disclosed, comprising an inner cladding region, at least two core structures disposed within the inner cladding region, and an outer cladding region or coating region disposed peripherally of the inner cladding region. Each core structure comprises a core region and an antiresonant region, the antiresonant region being composed of at least one capillary group, each capillary group comprising a plurality of capillaries, the capillaries in each capillary group being arranged annularly around the core region with the core region as the center. The capillaries in the antiresonant region are filled with the same optical fiber matrix, and the refractive index n3 of the antiresonant region is greater than the refractive index n2 of the inner cladding region, while the refractive index n1 of the core region is greater than the refractive index n4 of the outer cladding region or coating region. The optical fiber of the present invention facilitates high-density integration of core structures in a multi-core optical fiber, and has a large mode field area and a high high-order mode suppression ratio, achieving both high power and high beam quality.

Description

Technical Field

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

[0002] Thanks to its high efficiency, high beam quality, and excellent heat dissipation, fiber laser technology has flourished over the past 20 years, with improvements across all laser specifications. Furthermore, fiber itself offers high stability, high environmental adaptability, and ease of integration, advantages that have led to its widespread application in many fields. Despite this, it is now widely recognized in the industry that factors such as fiber nonlinear effects and mode instability restrict further increases in fiber laser system power. As research continues to deepen, numerous targeted suppression methods have been proposed, which have, to a certain extent, achieved the effect of raising the onset threshold, but have not fundamentally resolved the problem. For example, single-core fiber lasers (including total reflection mechanism and anti-resonance mechanism) are limited in power increase due to the nonlinear effect of fiber at extreme power. Research on multi-core optical fibers and lasers based on total reflection light guiding mechanism is mainly concentrated in the 1μm band. Research on multi-core optical fibers also includes communication bands. This type of multi-core optical fiber is used in the visible light band and faces the same problem as single-core optical fibers used in the visible light band. It is difficult to achieve both large mode field and high beam quality. In order to maintain high beam quality, the core and numerical aperture (NA) of the multi-core optical fiber need to be small. Such a small mode field area also limits the power level. In addition, multi-wavelength, high-power laser systems based on optical path combining are complex and costly, and 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 increasing the power of fiber laser systems. In recent years, research on multi-core fiber lasers based on the total internal reflection light guiding mechanism has become a hot topic. Research on high-power, high-brightness lasers has mainly focused on the 1μm band, with little research on the visible light band and mid-infrared. This is mainly because the commonly used quartz-based fiber has high phonon energy, making it unsuitable for visible light and mid-infrared lasing. At the same time, quartz-based fiber has high transmission loss in the mid-infrared band.

[0004] In addition, the emergence of multi-core optical fiber provides a new technical route for multi-wavelength lasers. Previous technical routes for multi-wavelength lasers include multi-wavelength semiconductor lasers, multi-wavelength lasers based on nonlinear effects (optical fiber, solid), and multi-wavelength lasers based on optical path combining. However, the above lasers have more or less shortcomings such as complex systems, high costs, and limited number of wavelengths and wavelength selection. Single-fiber multi-core fiber lasers not only enrich the number of wavelengths and the diversity of wavelength selection of multi-wavelength lasers, but also greatly simplify the complexity of the system and improve the system stability. However, multi-core fiber lasers based on the total reflection mechanism cannot take into account the advantages of large mode field and high beam quality.

[0005] It is widely believed in the field that if the spacing between the core structures of a multi-core optical fiber is too small, it is easy to cause mode coupling and increase crosstalk. In order to obtain weak coupling, the spacing between the core structures needs to be increased. This is not conducive to the high-density integration of the core structures in the multi-core optical fiber. For example, the patent application with publication number CN 117613647 A mentions that the multi-core optical fiber based on the total reflection light guiding mechanism must meet the following requirements: the minimum center-to-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] To address the technical issues existing in the prior art, the present invention proposes a multi-core, all-solid-state antiresonant fiber and a multi-wavelength fiber laser system. These technologies effectively avoid the problem that existing multi-core fibers require increasing the spacing between the core structures to achieve weak coupling, which hinders the high-density integration of the core structures within the multi-core fiber. The multi-core, all-solid-state antiresonant fiber proposed in the present invention facilitates high-density integration of the core structures within the multi-core fiber.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] In one aspect, a multi-core all-solid-state antiresonant optical fiber is provided, comprising an inner cladding region, at least two core structures disposed within the inner cladding region, and an outer cladding region or a coating region disposed periphery of the inner cladding region; each core structure comprises a core region and an antiresonant region, the antiresonant region being composed of at least one capillary group, each capillary group comprising a plurality of capillaries, the capillaries in each capillary group being arranged annularly around the core region with the core region as the center, the optical fiber matrix filled in each capillary in the antiresonant region being the same, the refractive index n3 of the antiresonant region being greater than the refractive index n2 of the inner cladding region, and the refractive index n1 of the core region being greater than the refractive index n4 of the outer cladding region or the coating region;

[0009] The structures and parameters of different core structures are the same or different from each other, and each core structure is a centrally symmetrical structure, and the center distance between each core structure is not less than 1 times the maximum core structure diameter.

[0010] Furthermore, the optical fiber matrix in the core region may or may not be doped with rare earth ions. Furthermore, 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, and dysprosium. Alternatively, 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. Alternatively, the optical fiber matrix in the core region may be doped with three or more rare earth ions. Furthermore, the types of rare earth ions doped in the optical fiber matrix in the core region of each core structure may be the same or different.

[0011] Furthermore, the shape, size and wall thickness of each capillary in the same capillary group in the same fiber core structure are the same as each other; the number of capillaries, the shape, size and wall thickness of the capillaries between different capillary groups in the same fiber core structure are the same as each other or different from each other; the number of capillary groups in different fiber core structures, the shape, size and wall thickness of the capillaries in each capillary group are the same as each other or different from each other.

[0012] Furthermore, the antiresonance region in each core structure includes a capillary group, each capillary group includes six capillaries, and the six capillaries are arranged in a ring around the core region with the core region as the center, and the wall thickness of each capillary is the same.

[0013] On the other hand, a multi-wavelength fiber laser system is provided, comprising the multi-core all-solid-state anti-resonant fiber described above.

[0014] Furthermore, a multi-wavelength fiber laser system includes a pump source, a high-reflection fiber Bragg grating (FBG), a gain fiber, a low-reflection fiber Bragg grating (FBG), and a cladding light filter. The gain fiber utilizes the aforementioned multi-core all-solid-state anti-resonance fiber. The fiber matrix of each core region of the multi-core all-solid-state anti-resonance fiber is doped with rare earth ions. The high-reflection fiber Bragg grating (FBG), the gain fiber, and the low-reflection fiber Bragg grating (LRFG) are sequentially connected, forming a resonant cavity between the high-reflection fiber Bragg grating and the low-reflection fiber Bragg grating. Pump light output by the pump source is coupled into the resonant cavity via one end of the high-reflection fiber Bragg grating (LRFG). Signal light output by the gain fiber is output via the low-reflection fiber Bragg 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-resonance band of the gain fiber. The high-order mode suppression ratio of the signal wavelength is required to be greater than 100. Furthermore, the pump source is a blue semiconductor laser. The fiber matrix of the core region of each core structure in the gain optical fiber is doped with a single rare earth ion holmium or dysprosium, that is, the fiber matrix of the core region of a part of the core structure is doped with holmium ions, and the fiber matrix of the core region of a part of the core structure is doped with dysprosium ions.

[0015] Furthermore, a multi-wavelength fiber laser system includes a multi-wavelength transmission fiber, which adopts the above-mentioned multi-core all-solid-state anti-resonance fiber, and the fiber matrix of each core region of the multi-core all-solid-state anti-resonance fiber is not doped with rare earth ions. The multi-wavelength transmission fiber is used for two or more lasers of different wavelengths, and the two or more lasers of different wavelengths are transmitted through different core regions respectively.

[0016] Furthermore, all regions of the multi-core all-solid-state antiresonant optical fiber, including the inner cladding region, the core region and the antiresonant region, use the same optical fiber matrix, which is ZBLAN. The components of ZBLAN include ZrF4, BaF2, LaF4, AlF3 and NaF.

[0017] Compared with the prior art, the technical effects of the present invention are:

[0018] The multi-core, all-solid-state antiresonant optical fiber proposed in the present invention comprises at least two core structures disposed within an inner cladding region, each core structure comprising a core region and an antiresonant region. This structural design effectively confines a transmitted light beam to the core region of each core structure. Furthermore, the spacing between the core structures of this multi-core, all-solid-state antiresonant optical fiber is unrestricted. Simulations of this multi-core, all-solid-state antiresonant optical fiber reveal that even when the core structures overlap, the transmitted light beam is still effectively confined to the core region of each core structure, regardless of current technological advancements. Taking into account the current limitations of fiber drawing processes, the present invention provides for non-overlapping core structures, with the center-to-center spacing between the core structures being no less than 1 times the maximum core structure diameter. This is significantly lower than the core spacing requirements for multi-core optical fibers in the prior art, such as those mentioned in patent application publication number CN 117613647 A, which stipulates that a multi-core optical fiber based on a total internal reflection light guiding mechanism must meet the following requirements: the minimum center-to-center spacing between any adjacent rare-earth-doped cores must be no 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 high-density integration of the core structure in the multi-core optical fiber.

[0019] The multi-core all-solid-state antiresonant optical fiber proposed by the present invention has the advantages of both high power and high beam quality.

[0020] The multi-wavelength fiber laser system of the present invention utilizes a fiber structure, which features a small size, high surface area ratio, and strong anti-interference capabilities. This provides advantages such as a simple and compact structure, high stability, and excellent heat dissipation. Other non-fiber-based multi-wavelength laser system solutions, however, lack the advantages of the present invention because the laser propagates in free space and is easily affected by the external environment.

[0021] The present invention utilizes a rare-earth-doped multi-core, all-solid-state antiresonant fiber as the gain fiber, employing an antiresonant light-guiding mechanism. Initially, the gain fiber design allows for a large mode area and a high high-order mode suppression ratio (HOMSR). This eliminates high-order modes during transmission (typically, a HOMSR greater than 100 is considered single-mode transmission), achieving both high power and high beam quality. However, multi-core fibers using a total internal reflection light-guiding mechanism, due to their inherent limitations, conflict between the large mode area designed for high power and high beam quality, particularly for short wavelengths. Consequently, the advantages of the present invention are lost. 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 or the description of the prior art. 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 the structures shown in these drawings without paying any creative work.

[0023] Figure 1 is a schematic cross-sectional view of a multi-core all-solid-state antiresonant optical fiber according to an embodiment;

[0024] Figure 2 Schematic diagram of the structure of a multi-wavelength fiber laser system in one embodiment;

[0025] Figure 3 A graph showing how the refractive index of the filling material in the core region and antiresonance region of a gain optical fiber designed in one embodiment varies with wavelength;

[0026] Figure 4 is a single-mode transmission characteristic diagram of a gain optical fiber designed in one embodiment, wherein Figure 4 (a) When d2 / d1=0.5, the fundamental modes (LP 01 ) The limiting loss changes with d1 / D, Figure 4 (b) When d1 / D=0.74, the fundamental mode (LP 01 ), higher order modes (LP 11 ) The limiting loss and the high-order mode suppression ratio (HOMER) change with d2 / d1, Figure 4 (c) When d1 / D=0.71, the fundamental mode (LP 01 ), higher order modes (LP 11 ) The limiting loss and higher-order mode suppression ratio (HOMER) change with d2 / d1;

[0027] Figure 5 : is the electric field distribution diagram of the six-core double-clad all-solid-state antiresonant optical fiber without rare earth ion doping obtained by simulation in one embodiment, wherein Figure 5 (a) LP in each core region 01 The electric field distribution diagram, Figure 5 (b) LP 11 The electric field distribution diagram;

[0028] Figure 6 LP of a six-core double-clad all-solid-state antiresonant fiber without rare earth ion doping obtained by simulation in one embodiment 01 Electric field distribution diagram and microstructure magnification diagram, where Figure 6 (a) LP of the six-core double-clad all-solid-state antiresonant fiber without rare earth ion doping at 543nm01 Electric field distribution diagram, Figure 6 (b) is an enlarged view of the microstructure of a six-core double-clad all-solid-state antiresonant fiber without rare earth ion doping.

[0029] Numbers in the figure:

[0030] 1 is the core region, 2 is the inner cladding region, 3 is the antiresonance region, and 4 is the outer cladding region or coating region;

[0031] 10 is a pump source, 20 is a pump source with a quartz pigtail, 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

[0032] 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] Reference Figure 1 The multi-core all-solid-state antiresonant 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;

[0034] Each fiber core structure includes a core region 1 and an antiresonance region 3. The antiresonance region 3 is composed of at least one capillary group, each capillary group includes multiple capillaries, and the capillaries in each capillary group are arranged in a ring around the core region with the core region as the center. 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.

[0035] Furthermore, the multi-core all-solid-state antiresonant optical fiber may further include an outer cladding region or coating region 4 disposed outside the inner cladding region 2. The inner cladding region 2 includes at least two core structures arranged in any shape, typically in a circular array. From the perspective of practical optical fiber drawing and application, the core structures must not overlap, i.e., the center-to-center spacing between the core structures must be no less than 1 times the maximum core structure diameter.

[0036] In one embodiment, a multi-core all-solid-state anti-resonant optical fiber is provided, wherein the optical fiber matrix of the core region 1 is doped with rare earth ions. The multi-core all-solid-state anti-resonant optical fiber doped with rare earth ions in the optical fiber matrix of the core region 1 can be used as a gain fiber for a multi-wavelength optical fiber laser system, wherein the rare earth ions can be any rare earth ions such as ytterbium, erbium, thulium, neodymium, holmium, samarium, praseodymium, and dysprosium, or can be co-doped with two rare earth ions such as erbium and ytterbium, praseodymium and ytterbium, or thulium and dysprosium, or can be doped with three or more rare earth ions; the rare earth ions doped in the optical fiber matrix of the core region of each core structure can be the same or different, and the doping situation can be designed according to actual needs.

[0037] Multi-core all-solid-state anti-resonant optical fiber can be doped with rare earth ions and the specific doping method of rare earth ions according to needs to achieve single-wavelength laser transmission or multi-wavelength laser transmission.

[0038] In one embodiment, a multi-core all-solid-state antiresonant optical fiber is provided, wherein the optical fiber matrix of the core region 1 is not doped with rare earth ions, and can be used as a multi-wavelength transmission optical fiber for a multi-wavelength optical fiber laser system.

[0039] In the multi-core, all-solid-state antiresonant optical fiber provided by the present invention, the antiresonant region 3 of the core structure is composed of at least one capillary group, each capillary group being composed of at least four capillaries. The capillaries can be single-tube structures or nested-tube structures, and are arranged in a ring-shaped pattern around the core region, equidistant and node-free. Each capillary in the capillary group has a certain wall thickness. The capillaries contained in the capillary group in the same core structure are generally of the same size and wall thickness. The diameters and wall thicknesses of the capillaries contained in the capillary groups in different core structures may vary.

[0040] The refractive index relationship of the filling materials (i.e., the fiber matrix) in all regions of a multi-core, all-solid-state antiresonant optical fiber is as follows: refractive index n3 of antiresonant region 3 > refractive index n2 of inner cladding region 2 = refractive index n1 of core region 1 > refractive index n4 of outer cladding or coating region 4. It should be noted that the filling material of the capillary interior and the inner cladding region can be the same or different.

[0041] In a preferred embodiment, all regions of the multi-core all-solid-state antiresonant optical fiber, including the inner cladding region 2, the core region 1, and the antiresonant region 3, utilize the same optical fiber matrix, namely, ZBLAN. The ZBLAN components include ZrF4, BaF2, LaF4, AlF3, and NaF. All regions of the multi-core all-solid-state antiresonant optical fiber, including the inner cladding region 2, the core region 1, and the antiresonant region 3, utilize the same optical fiber matrix. In addition to ZBLAN, other optical fiber matrices with lower phonon energy and capable of visible light lasing, such as fluorine-aluminum-based and fluorine-indium-based, may also be used.

[0042] The present invention is not limited to the number of core structures, the number of cladding structures (double cladding, triple cladding, etc.), or the arrangement of the cores. Persons skilled in the art can select and adjust the design based on their needs. Furthermore, the shape of the core region is also not limited and can be D-shaped, double-D-shaped, or a regular polygon.

[0043] Reference Figure 1 , a schematic cross-sectional view of a multi-core all-solid-state antiresonant optical fiber in one 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 within the outer tube. The capillaries in each core structure have the same wall thickness but different diameters. The design of the capillary wall thickness t in each core structure should follow the antiresonance 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, it is required that the pump wavelength be within the resonant band, the signal wavelength be within the anti-resonant band, and the high-order mode suppression ratio (HOMER) of the signal wavelength be no less than 100. HOMER is the high-order mode (LP) with the lowest loss. 11 mode) and the limiting loss value of the core fundamental mode (LP 01 mode) limits 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.

[0044] Another embodiment provides a multi-wavelength fiber laser system, which uses 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 for the pump source, a high-reflection fiber Bragg grating 30, a gain fiber 40, a low-reflection fiber Bragg grating 50, and a cladding light filter 60. The gain fiber 40 adopts the multi-core all-solid-state anti-resonant fiber proposed in any of the above embodiments. The fiber matrix of each core region of the multi-core all-solid-state anti-resonant 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 with a small optical fiber volume, a large volume-to-surface ratio, and strong anti-interference ability. Therefore, it has the advantages of simple and compact structure, high stability, and good heat dissipation.

[0045] The pump source with a quartz pigtail 20 is connected to one end of the high-reflection fiber Bragg grating 30, the other end of the high-reflection fiber Bragg 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 Bragg grating 50, the other end of the low-reflection fiber Bragg grating 50 is connected to one end of the cladding light filter 60, and the other end of the cladding light filter 60 is output to free space.

[0046] The pump light output by the pump source 10 passes through the pump source-sourced quartz pigtail 20 and the high-reflection fiber Bragg grating 30, then enters the resonant cavity formed between the high-reflection fiber Bragg grating 30 and the low-reflection fiber Bragg grating 50. It is absorbed by the gain fiber 40 and, at a certain pump light power, emits signal laser light of multiple wavelengths. The signal light is then output into space through the low-reflection fiber Bragg grating 50 and the cladding light filter 60. 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 antiresonant band of the gain fiber 40. The high-order mode suppression ratio of the signal wavelength is required to be greater than 100.

[0047] The optical fiber used for writing the high-reflection fiber Bragg grating 30 and the low-reflection fiber Bragg grating 50 is the gain fiber 40. The high-reflection fiber Bragg grating 30 and the low-reflection fiber Bragg grating 50 can be directly written on the gain fiber 40. The high-reflection fiber Bragg grating 30 is used for wavelength selection and providing higher feedback. A high-reflection fiber Bragg grating of the corresponding output wavelength is written inside each core region of the gain fiber 40. The low-reflection fiber Bragg grating is used to provide a certain degree of feedback and output signal light laser. A low-reflection fiber Bragg grating of the corresponding output wavelength is written inside each core region of the gain fiber 40. In this way, an all-fiber structure laser is constructed, making the system operation more stable and improving the system stability and robustness.

[0048] The center of the reflection band of the high-reflection fiber Bragg grating 30 is at the target lasing wavelength corresponding to the rare earth ion doped core region, the reflection bandwidth is about 3nm, and the reflectivity is about 99%.

[0049] Furthermore, the reflection band center of the low-reflection fiber Bragg grating is at the target lasing wavelength of the rare earth ion doped corresponding to the core region, the reflection bandwidth is ~1nm, and the reflectivity varies from 4% to 80%.

[0050] Furthermore, the optical fiber used to prepare the cladding light filter 60 is the same as the gain optical fiber 40 .

[0051] In one embodiment, based on Figure 2 The structure shown in FIG. 1 provides a multi-wavelength fiber laser system, specifically a dual-wavelength fiber laser system. In this embodiment, the pump source 10 is a blue light semiconductor laser, which is used to generate the pump laser of the visible light laser. The gain fiber 40 is a six-core double-clad all-solid-state anti-resonant fiber doped with rare earth ions, and its cross-sectional diagram is shown in FIG. Figure 1As shown, the rare earth ions doped into the fiber matrix in the core region of the gain fiber 40 can be holmium or dysprosium. Holmium ions are doped into the fiber matrix in the core regions of three core structures, while dysprosium ions are doped into the fiber matrix in the core regions of the other three core structures. Both rare earth ions can be pumped using the aforementioned pump source: holmium ions can be pumped at 543 nm, and dysprosium ions can be pumped at 575 nm. High-reflection fiber Bragg gratings 30 and low-reflection fiber Bragg gratings 50 are directly inscribed onto the gain fiber 40. A cladding light filter 60 is used to filter out residual pump light and high-order mode signal light in the cladding.

[0052] In this embodiment, the rare earth ions doped in the fiber matrix of the core region of the gain fiber 40 are holmium ions and dysprosium ions. Holmium ions can be excited at 543 nm, and dysprosium ions can be excited at 575 nm. This embodiment designs a six-core double-nested double-clad all-solid-state antiresonant fiber that supports dual-wavelength, high beam quality, and high power transmission. The fiber matrix of the core regions of three core structures is doped with holmium ions, and the fiber matrix of the core regions of the other three core structures is doped with dysprosium ions. The structure is as follows: Figure 1 All regions of the gain fiber 40, including the inner cladding region, the core region, and the antiresonance region, use the same fiber matrix, namely ZBLAN (ZrF4-BaF2-LaF4-AlF3-NaF), and the components of ZBLAN include ZrF4, BaF2, LaF4, AlF3, and NaF.

[0053] Furthermore, the gain fiber is filled with ZBLAN (ZrF4-BaF2-LaF4-AlF3-NaF) in all regions. The proportion of components in different regions is different. The required refractive index of the region is adjusted by adjusting the proportion of components. The specific refractive index of the filling material used in this embodiment varies with wavelength as shown in the following figure: Figure 3 As shown in the figure, 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. Double-clad all-solid-state antiresonant optical fiber (holmium ion and dysprosium ion doped), its structure is as follows Figure 1As shown in the figure, the specific parameters are: 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 diameter of the double-nested capillary in the antiresonance region is d1, and the inner diameter is d2. For a core structure with a transmission wavelength of 543 nm, the outer diameter d1 of the double-nested capillary in the antiresonance region is preferably 14.8 μm, and the inner diameter d2 is preferably 7.4 μm. For a core structure with a transmission wavelength of 575 nm, the outer diameter d1 of the double-nested capillary in the antiresonance region is preferably 14.2 μm, and the inner diameter d2 is preferably 8.662 μm. The capillary wall thickness t is 1.5 μm. The capillary wall thickness affects the transmission loss of the optical fiber, which further affects the power level of the output laser and the efficiency of the fiber laser.

[0054] The optimization process of gain fiber optimal value is as follows: Figure 4 As shown, Figure 4 (a) When d2 / d1=0.5, the fundamental modes (LP 01 ) The limiting loss changes with d1 / D, taking the wavelength fundamental mode (LP 01 ) The d1 / D value corresponding to the minimum loss value is the preferred value of d1 / D (0.74@543nm, 0.71@575nm in this embodiment), and then the preferred value of d1 is determined (14.8μm@543nm, 14.2μm@575nm in this embodiment). Figure 4 As can be seen in (a), the value of d1 / D is related to the fundamental mode (LP 01 ) The limiting loss value does not change regularly, and the optimal value can only be obtained through optimized design. Figure 4 (b) When d1 / D=0.74, the fundamental mode (LP 01 ), higher order modes (LP 11 ) Limit loss and high-order mode suppression ratio (HOMER) with d2 / d1, select the fundamental mode (LP 01 ) When the limiting loss is small and the high-order mode suppression ratio (HOMER) value is greater than 100, the corresponding d2 / d1 value is the preferred value of d2 / d1 (0.5 in this embodiment), and then the preferred value of d2 is determined (7.4μm in this embodiment). Figure 4 (c) When d1 / D=0.71, the fundamental mode (LP 01 ), higher order modes (LP 11 ) Limit loss and high-order mode suppression ratio (HOMER) with d2 / d1, select the fundamental mode (LP 01) When the limiting loss is small and the high-order mode suppression ratio (HOMER) value is greater than 100, the corresponding d2 / d1 value is the preferred value of d2 / d1 (0.61 in this embodiment), and then the preferred value of d2 is determined (8.662μm in this embodiment).

[0055] In one embodiment, a multi-wavelength fiber laser system is provided, comprising a multi-core all-solid-state anti-resonant fiber, wherein the fiber matrix of each core region of the multi-core all-solid-state anti-resonant fiber is not doped with rare earth ions, and the multi-wavelength transmission fiber is used for two or more lasers of different wavelengths, and the two or more lasers of different wavelengths are transmitted through different core regions respectively. In a specific embodiment, Figure 5 As shown, Figure 5 The electric field distribution diagram of a six-core double-clad all-solid-state antiresonant optical fiber without rare earth ion doping obtained by simulation in one embodiment is shown in FIG. Figure 5 (a) LP in each core region 01 The electric field distribution diagram, Figure 5 (b) LP 11 Electric field distribution diagram. Figure 5 The structure of the six-core double-clad all-solid-state antiresonant fiber without rare earth ion doping is similar to Figure 1 The structures and structural parameter settings of the embodiments shown are exactly the same, and the center spacing between the core structures is 1.5 times the diameter of the core structure. The only difference is that the core regions are not doped with rare earth ions, and the core regions of three core regions are used to transmit 575nm, and the core regions of the other three core regions are used to transmit 543nm. Figure 5 (a) It can be seen that the fundamental mode energy is well confined in each fiber core, and there is no obvious energy distribution in the non-core area, that is, the confinement loss is small. Figure 5 (b) LP 11 The electric field distribution diagram of Figure 5 LP shown in (a) 01 The electric field distribution diagram of the fiber core is in sharp contrast. 11 The mode will leak out through phase matching coupling with the cladding mode, that is, the confinement loss is large.

[0056] like Figure 6 As shown, Figure 6 LP of a six-core double-clad all-solid-state antiresonant fiber without rare earth ion doping obtained by simulation in one embodiment 01 Electric field distribution diagram and microstructure magnification diagram, each fiber core structure parameter and Figure 5 The difference of the six-core double-clad all-solid-state antiresonant optical fiber without rare earth ion doping in the embodiment shown is: Figure 6 The center distance between each core structure is 0.65 times the diameter of the core structure, and there is a great degree of overlap between the core structures. Figure 6(a) LP of the six-core double-clad all-solid-state antiresonant fiber without rare earth ion doping at 543nm 01 Electric field distribution diagram, you can see the LP in each fiber core area 01 The modes can still be well confined to their respective core regions. Figure 6 (b) is an enlarged view of the microstructure of a six-core double-clad all-solid-state antiresonant fiber without rare earth ion doping. It can be seen that although the core structures overlap severely, the LP in each core structure is 01 The modes can still be well confined to their respective core regions.

[0057] In summary, the multi-core all-solid-state anti-resonant optical fiber proposed in the present invention is not limited by the spacing between the core structures, if the current technological level is not taken into account. Even if the core structures overlap with each other, the simulation results show that the transmitted light beam can be well constrained in the core area of ​​each core structure. Taking into account the current technological limitations of drawing optical fibers, the present invention sets the core structures not to overlap with each other. The multi-core all-solid-state anti-resonant optical fiber proposed in the present invention is more conducive to the high-density integration of the core structure in the multi-core optical fiber.

[0058] Matters not covered by the present invention are known technologies.

[0059] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0060] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements are intended to fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. For example, gain fibers with different structural parameters can be designed, and the dopant ions and pump wavelengths can be varied to achieve laser output at other signal wavelengths. For example, using a 0.8μm laser pump and doping with neodymium ions can achieve 1μm and 1.3μm laser output; using a 1.1μm laser pump and doping with holmium ions can achieve 1.2μm and 2μm laser output; using a 793nm laser pump and doping with erbium ions can achieve 2.7μm laser output; and using a 980nm laser pump and doping with erbium ions can achieve 1.55μm laser output. These results have been verified in step-index fibers. It should be noted that different laser ions in the fiber may require different pump wavelengths, and the present invention can also meet these requirements by designing all pump laser wavelengths within the resonant band during fiber design. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-core all-solid-state antiresonant optical fiber, characterized in that: The fiber comprises an inner cladding region, at least two core structures arranged inside the inner cladding region, and an outer cladding region or a coating region arranged outside the inner cladding region; Each fiber core structure includes a core region and an antiresonance region. The antiresonance region is composed of at least one capillary group, each capillary group includes multiple capillaries, and the capillaries in each capillary group are arranged in a ring around the core region with the core region as the center. The optical fiber matrix filled in each capillary in the antiresonance region is the same, and the refractive index n3 of the antiresonance region is greater than the refractive index n2 of the inner cladding region, and the refractive index n1 of the core region is greater than the refractive index n4 of the outer cladding region or the coating region. The structures and parameters of different core structures are the same or different from each other, and each core structure is a centrally symmetrical structure, and the center distance between each core structure is not less than 1 times the maximum core structure diameter.

2. The multi-core all-solid-state antiresonant optical fiber according to claim 1, characterized in that: The optical fiber matrix in the core region is doped with rare earth ions.

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

4. The multi-core all-solid-state antiresonant optical fiber according to claim 1, 2 or 3, characterized in that: The capillaries in the same capillary group in the same fiber core structure have the same shape and wall thickness; the number of capillaries, the shape of the capillaries, and the wall thickness of the capillaries in different capillary groups in the same fiber core structure are the same as or different from each other; The number of capillary groups in different core structures, and the shape and wall thickness of the capillaries in each capillary group are the same or different from each other.

5. Multi-wavelength fiber laser system, characterized in that, It comprises the multi-core all-solid-state antiresonant optical fiber as claimed in claim 1.

6. The multi-wavelength fiber laser system according to claim 5, characterized in that: The invention comprises a pump source, a high-reflection fiber Bragg grating (FBG), a gain fiber, a low-reflection fiber Bragg grating (FBG), and a cladding light filter. The gain fiber adopts the multi-core all-solid-state anti-resonance fiber as claimed in claim 1. The fiber matrix of each core region of the multi-core all-solid-state anti-resonance fiber is doped with rare earth ions. The high-reflection fiber Bragg grating (FBG), the gain fiber, and the low-reflection fiber Bragg grating (LRG) are connected in sequence. A resonant cavity is formed between the high-reflection fiber Bragg grating and the low-reflection fiber Bragg grating. Pump light output by the pump source is coupled into the resonant cavity through one end of the high-reflection fiber Bragg grating. Signal light output by the gain fiber is output through the low-reflection fiber Bragg 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-resonance 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, characterized in that: The invention comprises a multi-wavelength transmission optical fiber, wherein the multi-wavelength transmission optical fiber adopts the multi-core all-solid-state anti-resonance optical fiber as claimed in claim 1, wherein the optical fiber matrix of each core region of the multi-core all-solid-state anti-resonance optical fiber is not doped with rare earth ions, and the multi-wavelength transmission optical fiber is used for two or more lasers of different wavelengths, and the two or more lasers of different wavelengths 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-state antiresonant optical fiber, including the inner cladding region, the core region and the antiresonant 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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