Bending-resistant all-solid-state anti-resonance optical fiber with double-cladding structure

Abstract

The invention discloses a bending-resistant all-solid-state anti-resonance optical fiber with a double-cladding structure. The radial section of the bending-resistant all-solid-state anti-resonance optical fiber sequentially comprises a fiber core, an anti-resonance unit, a bending-resistant unit and a cladding unit from inside to outside, the anti-resonance unit comprises a plurality of anti-resonance rings which are uniformly distributed along the periphery of the fiber core in the circumferential direction, and each anti-resonance ring is tangent to the fiber core; the anti-bending unit comprises a plurality of anti-bending round bars, and any anti-bending round bar is located on the outer side of every two adjacent anti-resonant rings and does not make contact with the anti-resonant rings. According to the all-solid-state anti-resonant optical fiber, through reasonable arrangement of component structures, the limiting loss of a fundamental mode in a bending state is reduced, meanwhile, a high high-order mode rejection ratio is kept, the utilization efficiency of a traditional all-solid-state anti-resonant optical fiber on pump light is improved, and the light-light conversion efficiency of high-power optical fiber laser can be further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fibers, and in particular relates to a double-cladding structured all-solid-state anti-resonance optical fiber with anti-bending performance. Background Art

[0002] The rapid development of high-end industrial manufacturing and laser medical treatment has put forward higher and higher requirements on the output power of fiber lasers. In order to suppress nonlinear effects such as SBS and SRS under high-power output, the nonlinear gain coefficient can be reduced by increasing the mode field area. However, due to the requirements for the output laser beam quality, the mode field area of ​​traditional step-index optical fibers cannot be increased indefinitely. In order to increase the mode field area of ​​single-mode laser optical fibers, a large mode field optical fiber with a fully solid-state anti-resonant structure is proposed.

[0003] The transmission principle of all-solid-state antiresonant fiber is based on its unique structural characteristics. There are several antiresonant rings with high refractive index in the fiber cladding of all-solid-state antiresonant fiber. The thickness of this antiresonant ring is usually in the order of the transmission wavelength, ranging from hundreds of nanometers to several microns. This size selection ensures that the antiresonant ring can effectively interfere with the incident light wave. When the light wave is reflected and propagated multiple times in the ring, the reflectivity of the specific wavelength is enhanced due to the interference of the light beam phase difference. Since the conditions for the transmission of the reflected light wave in the ring are similar to those of the Fabry-Perot (FP) cavity, it also exhibits a wide-spectrum reflection characteristic. Therefore, the interference destructive condition that satisfies the antiresonant transmission wavelength is: Where λm is the antiresonant transmission wavelength, t is the thickness of the antiresonant ring, n1 and n0 represent the refractive index of the antiresonant ring and cladding materials respectively, and m is a positive integer.

[0004] Another significant advantage of all-solid-state antiresonant fiber is that it provides a solution for large-mode field transmission with high beam quality. By using the mode coupling principle, the high-order modes transmitted in the core are selectively filtered out, thereby improving the beam quality. According to Patrick.U's correction of the effective refractive index matching condition of the Marcatili-Schmeltzer mode, when the ratio of the inner diameter of the cladding antiresonant ring to the core diameter is 0.68, the best filtering effect of the core high-order mode can be achieved. Rare earth ions can be doped in the all-solid core diameter, so that it can be used as a gain medium in fiber laser systems. This solid antiresonant fiber suppresses the high-order mode components of the laser on the basis of a large core diameter, and can achieve high-power fundamental mode laser output.

[0005] At present, theoretical simulation can achieve single-mode laser output under the condition of mode field diameter of 124μm, showing unparalleled large mode field single-mode characteristics, but practical use still faces some difficulties. When the fiber bending loss is large, it cannot be coiled in a small size, losing the advantages of fiber-specific flexibility and small size integration. In addition, the high-order mode filtering effect of the anti-resonance structure will be greatly reduced under bending conditions, which is not conducive to improving the output beam quality. This sensitivity to bending limits the application of all-solid-state anti-resonance structure optical fibers in certain small spaces or devices. Therefore, it is urgent to develop all-solid-state anti-resonance optical fibers with anti-bending capabilities. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a double-clad all-solid-state antiresonant optical fiber with anti-bending properties, so as to solve the problems that the optical fiber cannot be coiled in a small size, and the high-order mode filtering effect of the antiresonant structure is poor under bending conditions, resulting in a decrease in the output beam quality.

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

[0008] A double-cladding all-solid anti-resonance optical fiber with anti-bending performance, wherein the radial cross section includes a fiber core, an anti-resonance unit, an anti-bending unit and a cladding unit in sequence from the inside to the outside; the anti-resonance unit includes a plurality of anti-resonance rings uniformly arranged along the outer circumference of the fiber core, and each anti-resonance ring is tangent to the fiber core; the anti-bending unit includes a plurality of anti-bending round rods, and any anti-bending round rod is located outside each of two adjacent anti-resonance rings and does not contact the anti-resonance rings.

[0009] Preferably, the anti-resonance unit includes 6 anti-resonance rings, and the anti-bending unit includes 6 anti-bending round rods.

[0010] Preferably, the ratio of the inner diameter of the antiresonance ring to the diameter of the fiber core is 0.55-0.75.

[0011] Preferably, the ratio of the inner diameter of the antiresonance ring to the diameter of the fiber core is 0.68.

[0012] Preferably, the diameter of the fiber core is 40 to 80 μm, the thickness of the anti-resonance ring is 0.5 to 4 μm, and the diameter of the anti-bending round rod is 10 to 30 μm.

[0013] Preferably, the diameter of the fiber core is 50 μm, the thickness of the anti-resonance ring is 0.8-3 μm, and the diameter of the anti-bending round rod is 10 μm.

[0014] Preferably, the distance between adjacent anti-bending round rods and the anti-resonance ring is at least 5 μm.

[0015] Preferably, the coating unit comprises, from inside to outside, an inner coating layer, an outer coating layer and a protective layer.

[0016] Preferably, the cross section of the inner cladding is a regular octagon.

[0017] Preferably, the refractive index of the protective layer is n c >Anti-resonance ring refractive index n arf >Inner cladding refractive index n1 = core refractive index n0 > Outer cladding refractive index n2 > Anti-bending rod refractive index n b .

[0018] Compared with the prior art, the advantages of the present invention are:

[0019] (1) The present invention is a double-clad all-solid-state anti-resonant optical fiber with anti-bending performance. By reasonably setting the component structure, the limiting loss of the fundamental mode under the bending state is reduced, while maintaining a high high-order mode suppression ratio, thereby improving the utilization efficiency of the traditional all-solid-state anti-resonant optical fiber for pump light, and helping to further improve the light-to-light conversion efficiency of high-power fiber lasers.

[0020] (2) The present invention is a double-cladding structure all-solid-state anti-resonant optical fiber with anti-bending performance. By rationally setting the component structure, the effective refractive index of the cladding mode is effectively regulated, and the high-order mode LP11 of the core is coupled and filtered with the fundamental mode in the anti-resonant ring, which is beneficial to the single-mode operation in the core of the optical fiber.

[0021] (3) The present invention provides a double-clad all-solid anti-resonance optical fiber with anti-bending performance. By reasonably setting the component structure, when the bending radius is 0.3m, the bending loss is reduced from 0.0083 of the all-solid anti-resonance optical fiber with a traditional structure to 0.0043.

[0022] (4) The present invention provides a double-clad all-solid-state antiresonant optical fiber with anti-bending performance. By reasonably setting the component structure, under the bending condition of a bending radius of 0.4-0.7m, the high-order mode suppression ratio of the anti-bending all-solid-state antiresonant optical fiber is significantly improved compared with the traditional non-anti-bending round rod structure, indicating that the double-clad all-solid-state antiresonant optical fiber with an anti-bending structure has a better high-order mode filtering effect under bending conditions, which means that it has better single-mode performance under bending conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 It is a schematic structural diagram of the double-cladding structure all-solid-state anti-resonance optical fiber with anti-bending performance of the present invention;

[0025] Figure 2is the lateral refractive index distribution of the optical fiber of the present invention;

[0026] Figure 3 The influence of the bending radius of the optical fiber of the present invention on the fundamental mode limiting loss;

[0027] Figure 4 The effect of the bending radius of the optical fiber of the present invention on the high-order mode suppression ratio;

[0028] Figure 5 The mode field distribution of the optical fiber fundamental mode and high-order mode of the present invention;

[0029] The symbols in the figure represent:

[0030] 1—inner cladding, 2—outer cladding, 3—protective layer, 4—antiresonance ring, 5—bending-resistant round rod, 6—fiber core DETAILED DESCRIPTION

[0031] The invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the invention.

[0032] It should be noted that the directional terms mentioned in this article, such as "inner cavity", "inner periphery", "inner wall" and "outside", are consistent with the specific directions on the paper of the drawings in the specification or the corresponding directions of the space shown in the drawings; all components and equipment in the present invention, unless otherwise specified, are all components and equipment known in the prior art.

[0033] Example

[0034] The present embodiment discloses a double-cladding structured all-solid anti-resonant optical fiber with anti-bending performance, wherein the radial cross section thereof includes, from the inside to the outside, a fiber core 6, an anti-resonance unit, an anti-bending unit, and a cladding unit; the anti-resonance unit includes a plurality of anti-resonance rings 4 uniformly arranged along the outer periphery of the fiber core 6, and each anti-resonance ring 4 is tangent to the fiber core 6; the anti-bending unit includes a plurality of anti-bending round rods 5, and any anti-bending round rod 5 is located outside each of two adjacent anti-resonance rings 4 and does not contact the anti-resonance rings 4;

[0035] Its function is to reduce the limiting loss of the fundamental mode in the bending state while maintaining a high high-order mode suppression ratio, thereby improving the utilization efficiency of the pump light by the traditional all-solid-state anti-resonant fiber, and helping to further improve the light-to-light conversion efficiency of high-power fiber lasers. Figure 2 The figure shows the refractive index profile distribution of the optical fiber cross section through the center of the circle in the horizontal and vertical directions.

[0036] The coating unit of this embodiment includes an inner cladding 1, an outer cladding 2 and a protective layer 3 from the inside to the outside. The surface of the inner cladding 1 is a regular octagon. The coating materials of the outer cladding 2 and the protective layer 3 are formed by high-temperature coating and ultraviolet curing.

[0037] The anti-resonance unit of this embodiment includes six anti-resonance rings 4, and the anti-bending unit includes six anti-bending round rods 5. The ratio of the inner diameter of the anti-resonance ring 4 to the diameter of the fiber core 6 is 0.55-0.75, preferably 0.68.

[0038] The diameter of the fiber core 6 disclosed in this embodiment is 40-80 μm, preferably 50 μm; the thickness of the anti-resonance ring 4 is 0.5-4 μm, preferably 0.8-3 μm; the diameter of the anti-bending round rod 5 is 10-30 μm, preferably 10 μm; the spacing between adjacent anti-bending round rods 5 and anti-resonance rings 4 is at least 5 μm, which is 5 μm in this embodiment.

[0039] The refractive index of the protective layer 3 in this embodiment is n c >Anti-resonance ring 4 refractive index n arf >Inner cladding 1 refractive index n1 = core 6 refractive index n0 > Outer cladding 2 refractive index n2 > Anti-bending round rod 5 refractive index n b .

[0040] The fiber core 6 of this embodiment is composed of SiO2, Al2O3, P2O5, Si F4 and RE2O3, wherein RE is a lanthanide trivalent rare earth ion, and Yb 3+ , Er 3+ 、Ho 3+ , Pr 3+ 、Dy 3+ One or more of the following: the inner cladding 1 is made of SiO2, the antiresonance ring 4 is made of SiO2 and GeO2, the anti-bending round rod 5 is made of SiO2 and B2O3 or of SiO2 and SiF4, the outer cladding 2 is made of a low refractive index polymer, and the protective layer 3 is made of a high refractive index polymer.

[0041] Consider the refractive index n of pure quartz glass 石英 is 1.4572, and considering the first-order antiresonant waveguide with a wide passband, the C of Ge-doped quartz glass prepared by the MCVD method Ge Content <15mol.%, n arf The range of variation can be between 1.4572-1.4850. arf Difference Δn from the core refractive index n0 arf =n arf -n0 ranges from 0 to 0.0278. The t value comparison table of the present invention is as follows:

[0042] Table 1 t value comparison table

[0043]

[0044]

[0045] Figure 3 The figure shows the transmission mode field simulation results of this embodiment using the finite element simulation software COMSOL Multiphysics. The simulation process uses a mode analysis of the optical fiber cross section. During the simulation, the optical fiber of the embodiment is firstly structurally modeled, and the anti-resonance ring, the anti-bending round rod structure and the surrounding narrow area are divided using triangles with a maximum grid unit of λ / 5. The inner cladding, the core, and the outer cladding are divided using triangles with a maximum grid unit of λ / 4. In addition, a perfect matching layer PML is added to the outside of the outer cladding to leak the simulated outer cladding light and eliminate the influence of scattering. The field distribution of the fundamental mode (LP01) and the first high-order mode (LP11) of the simulation results are shown in FIG. Figure 3 It can be seen that through the design of this structure, the effective refractive index of the cladding mode is effectively regulated, and the high-order mode LP11 of the core is coupled and filtered out with the fundamental mode in the antiresonant ring, which is beneficial to the single-mode operation in the core of the optical fiber.

[0046] Figure 4 The figure shows the fundamental mode limiting loss of the bending-resistant double-clad Yb-doped all-solid anti-resonant optical fiber in the embodiment at a bending radius of 0.3-0.7m. It can be seen that compared with the traditional non-bending round rod structure, the fundamental mode bending loss of the bending-resistant all-solid anti-resonant optical fiber is significantly reduced. The bending loss of the optical fiber is defined as the difference between the fundamental mode limiting loss under bending conditions and the fundamental mode limiting loss in a straight state. When the bending radius is 0.3m, the bending loss is reduced from 0.0083 of the all-solid anti-resonant optical fiber with a traditional structure to 0.0043.

[0047] Figure 5 The figure shows the high-order mode suppression ratio of the bend-resistant double-clad ytterbium-doped all-solid-state antiresonant optical fiber in the embodiment with a bending radius of 0.3-0.7 m. It can be seen that under the bending condition of a bending radius of 0.4-0.7 m, the high-order mode suppression ratio of the bend-resistant all-solid-state antiresonant optical fiber is significantly improved compared with the traditional non-bending anti-resonant round rod structure, indicating that the double-clad all-solid-state antiresonant optical fiber with a bend-resistant structure has better high-order mode filtering effect under bending conditions, which means that it has better single-mode performance under bending conditions.

[0048] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0049] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0050] In addition, the various different implementation modes disclosed in this solution may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the content invented by the present disclosure.

Claims

1. A double-clad all-solid anti-resonant optical fiber with bending resistance, characterized in that: The radial cross section includes, from inside to outside, a fiber core (6), an anti-resonance unit, an anti-bending unit and a cladding unit; The anti-resonance unit comprises a plurality of anti-resonance rings (4) uniformly arranged along the circumference of the fiber core (6), and each of the anti-resonance rings (4) is tangent to the fiber core (6); The anti-bending unit comprises a plurality of anti-bending round bars (5), and any of the anti-bending round bars (5) is located outside each of two adjacent anti-resonance rings (4) and does not contact the anti-resonance rings (4).

2. The double-clad all-solid anti-resonant optical fiber with bending resistance as claimed in claim 1, characterized in that: The anti-resonance unit comprises six anti-resonance rings (4), and the anti-bending unit comprises six anti-bending round bars (5).

3. The double-clad all-solid anti-resonant optical fiber with bending resistance as claimed in claim 2, characterized in that: The ratio of the inner diameter of the anti-resonance ring (4) to the diameter of the fiber core (6) is 0.55-0.

75.

4. The double-clad all-solid anti-resonant optical fiber with bending resistance as claimed in claim 3, characterized in that: The ratio of the inner diameter of the anti-resonance ring (4) to the diameter of the fiber core (6) is 0.

68.

5. The double-clad all-solid anti-resonant optical fiber with bending resistance as claimed in claim 4, characterized in that: The diameter of the fiber core (6) is 40 to 80 μm, the thickness of the anti-resonance ring (4) is 0.5 to 4 μm, and the diameter of the anti-bending round rod (5) is 10 to 30 μm.

6. The double-clad all-solid anti-resonant optical fiber with bending resistance as claimed in claim 5, characterized in that: The diameter of the fiber core (6) is 50 μm, the thickness of the anti-resonance ring (4) is 0.8-3 μm, and the diameter of the anti-bending round rod (5) is 10 μm.

7. The double-clad all-solid anti-resonant optical fiber with bending resistance as claimed in claim 6, characterized in that: The distance between adjacent anti-bending round rods (5) and the anti-resonance ring (4) is at least 5 μm.

8. The double-clad all-solid anti-resonant optical fiber with bending resistance according to any one of claims 1 to 7, characterized in that: The coating unit comprises, from inside to outside, an inner coating layer (1), an outer coating layer (2) and a protective layer (3).

9. The double-clad all-solid anti-resonant optical fiber with bending resistance as claimed in claim 8, characterized in that: The surface of the inner cladding (1) is a regular octagon.

10. The double-clad all-solid anti-resonant optical fiber with bending resistance according to claim 9, characterized in that: The protective layer (3) has a refractive index n c >Anti-resonance ring (4) refractive index n arf >Inner cladding (1) refractive index n1 = core (6) refractive index n0 > Outer cladding (2) refractive index n2 > Anti-bending round rod (5) refractive index n b .

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