CN201083847Y - Refractive index anti-guiding multi-core fiber - Google Patents

Abstract

A refractive index anti-guiding multi-core optical fiber includes multiple cores and a cladding region, wherein the cladding region includes an inner cladding region and an outer cladding region, wherein multiple refractive index anti-guiding cores and multiple sub-wavelength diameter cores located between the refractive index anti-guiding cores are linearly arranged in the inner cladding region; the refractive index anti-guiding cores are composed of two coaxial parts of a low refractive index in the middle and a high refractive index in the periphery, the refractive index of the inner cladding region is less than the refractive index of the refractive index anti-guiding core and the sub-wavelength diameter core, but greater than the refractive index of the outer cladding region; the inner cladding region and the outer cladding region are both composed of solid materials with uniformly distributed refractive indices. The utility model can realize phase locking of multiple cores, and can improve the bending performance of the multi-core optical fiber, and can be applied in the fields of high-power optical fiber amplifiers, lasers, etc.

Description

Refractive index anti-guiding multi-core fiber

technical field

The utility model relates to an optical fiber, in particular to a refractive index anti-guiding multi-core optical fiber which is not sensitive to bending.

Background technique

High-power fiber lasers have been increasingly widely used in laser processing, laser medical treatment, laser radar, laser ranging and many other aspects due to their excellent performance and value-for-money price. Under the same output power, fiber lasers have advantages in beam quality, reliability, and volume. In addition, due to the reduction in fiber cost and the ease of streamlining and mass production, this not only arouses the interest of scientists, but also It has attracted great attention from industry experts.

Fiber lasers were first proposed in the 1960s, but progress has been slow until the development and application of low-loss fiber manufacturing technology and semiconductor lasers brought new prospects for fiber lasers. Fiber lasers use doped fibers as the laser medium. Compared with bulk laser media, fiber lasers have the following significant advantages: the medium is slender and easy to dissipate heat; the waveguide structure of the fiber is easy to achieve single transverse mode; it is easy to achieve high efficiency and high power. In recent years, the research and development of cladding pumping technology based on double-clad fiber has enabled the output power of fiber laser to exceed kW, which has broad application prospects in the fields of industry and communication.

The size of the fiber core has a great relationship with the output power. The larger the core, the greater the power that can be transmitted, while the smaller the core, the greater the transmitted power will produce nonlinear effects, affect the output power of the fiber, and even cause damage to the fiber. Therefore, in the double-clad fiber, the core of the fiber should be increased as much as possible under the premise of ensuring the quality of the output beam. However, in the general double-clad rare-earth-doped fiber, the increase of the core will affect the beam quality, resulting in the failure of the fiber laser and the amplifier. Multimode output, so the degree of enlargement of the fiber core is limited.

Microstructured fiber (MF) is composed of a two-dimensional photonic crystal whose lattice constant is on the order of the wavelength of light, that is, a silica fiber array regularly arranged with air holes constitutes the cladding of the fiber, and the core of the fiber is Consists of a defect that breaks the periodicity of the cladding structure. Compared with traditional optical fibers, microstructured optical fibers have many characteristics, which effectively expand and increase the application fields of optical fibers.

Another way to increase power while maintaining high beam quality is beam combining. Today, the research on coherent beam combining technology of high-power fiber lasers has become one of the international research hotspots. Countries such as the United States, Germany and France are very encouraging and supporting the development of such research. At present, researchers at home and abroad have proposed a variety of coherent bundling technologies, mainly including: main oscillation amplification (MOPA) technology, multi-core fiber self-assembly technology, all-fiber bundling technology, spectral bundling technology and external cavity coherent bundling technology . Among them, the multi-core fiber self-assembly technology is a relatively simple method. This method couples the evanescent waves of the adjacent fiber core transmission beams to achieve phase locking. However, the evanescent wave coupling is weak, and it is proposed to use the leaky wave of the refractive index anti-guiding structure to improve the coupling. In 2002, Raymond J.Beach and others from Livermore Laboratory in the United States proposed the design of ribbon optical fiber with anti-refractive index guidance, which uses leaky waves to improve the coupling of multiple fibers. By adding fiber cores, this method can achieve output power calibration. While amplifying, maintain excellent beam quality [J.Opt.Soc.Am.B 19(7)1521-1534, 2002]. Recently Feng.X. et al prepared 16-core refractive index anti-guiding multi-core fiber by stacking method, but this fiber is very sensitive to bending [Electronics Letters 40(12)10-11, 2004].

Recently, the fiber diameter obtained by Tong Limin of Zhejiang University and others using the two-step drawing method can be as low as 50nm, and the fiber loss is kept low [Nature 426 816-819, 2003]. Shanghai Jiao Tong University, Chen Xianfeng and others summed up the experience of the predecessors and proposed a strip-shaped electric heating furnace tapering method. Using this new tapering method, the diameter can be as low as 650nm and the length can reach more than ten centimeters. Order of magnitude, sub-wavelength diameter fiber with optical loss around 0.1dB/cm [Opt.Express 14(12)5055-5060.2006]. This fiber has a strong evanescent field, which can be widely used in many fields.

Contents of the invention

The purpose of the utility model is to overcome the deficiency that the refractive index anti-guiding optical fiber is sensitive to bending, and provide a refractive index anti-guiding multi-core optical fiber with improved bending performance. The multi-core optical fiber can effectively couple multiple fiber cores, and is insensitive to bending, and can be used in fields such as high-power fiber laser bundles.

The technical solution of the utility model is as follows:

A refractive index anti-guiding multi-core optical fiber, comprising multiple cores and cladding regions, characterized in that the cladding regions include an inner cladding region and an outer cladding region, and are linearly arranged in the inner cladding region There are multiple refractive index anti-guiding cores and multiple sub-wavelength diameter cores between the refractive index anti-guiding cores; The high refractive index coaxial two-part material, the refractive index of the inner cladding region is smaller than the refractive index of the anti-guiding core and the sub-wavelength diameter core, and greater than the refractive index of the outer cladding region; the inner cladding region and the outer cladding region are composed of a solid material with a uniform distribution of refractive index.

The core diameter of the refractive index anti-guiding core is on the order of microns, the core diameter of the sub-wavelength diameter core is on the order of hundreds of nanometers, and the distance between the sub-wavelength diameter core and the refractive index anti-guiding core is on the order of wavelength .

The refractive index anti-guiding cores are closely arranged with each other.

The shape of the inner cladding region is rectangle or polygon.

The low-refractive-index part of the refractive index anti-guiding fiber core is doped with at least one of rare earth elements neodymium, erbium, ytterbium, thulium, and lanthanum, and at the same time doped with at least one of aluminum, phosphorus, and fluoride Quartz glass, silicate glass, phosphate glass, or tellurite glass.

The matrix material of the sub-wavelength diameter fiber core, the inner cladding region and the outer cladding region is quartz glass, silicate glass, phosphate glass, or tellurate glass.

In order to ensure effective coupling of multiple cores, the core diameter of the sub-wavelength diameter core is on the order of hundreds of nanometers, and the distance between the sub-wavelength diameter core and the refractive index anti-guiding core is on the order of wavelength.

Description of drawings

FIG. 1 is a schematic cross-sectional view of an optical fiber in Embodiment 1 of the present invention.

Fig. 2 is a schematic cross-sectional view of an optical fiber in Embodiment 3 of the present invention.

FIG. 3 is a schematic cross-sectional view of an optical fiber in Embodiment 4 of the present utility model.

Detailed ways

The utility model will be described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the utility model should not be limited thereby.

Example 1:

Please refer to FIG. 1 . FIG. 1 is a schematic cross-sectional view of an optical fiber in Embodiment 1 of the present utility model. This is that there are 5 refractive index anti-guiding cores 2 arranged linearly in the inner cladding region 6, and the sub-wavelength diameter fiber cores 5 are located between the refractive index anti-guiding cores 2, and the inner cladding region 6 covers the outer cladding region 7 refractive index anti-guiding multi-core fiber. The shape of the inner cladding region 6 is rectangular, the size is 60 μm×40 μm, and the diameter of the outer cladding region 7 is 125 μm. The high refractive index part 3 in the refractive index anti-guiding fiber core 2 is composed of shott SF16 silicate glass with a refractive index of 1.637 and a radius of 1.6 μm, and the low refractive index part 4 is composed of shott F7 silicate glass doped with 3.0wt% neodymium oxide, the refractive index is 1.626, and the radius is 1 μm. The material of the sub-wavelength diameter core 5 is the same as that of the high refractive index part 3 in the refractive index anti-guiding core 2. The core diameter is 100 nm, and the distance from the fiber axis The distance is 1 μm. The inner cladding region 6 is composed of shottF2 silicate glass with a refractive index of 1.612, and the material of the outer cladding region 7 is quartz with a refractive index of 1.45. Experimental results show that if the sub-wavelength diameter core 5 is not introduced, bending has a great influence on the optical fiber 1, and after the sub-wavelength diameter core 5 is introduced, the bending performance of the optical fiber 1 under the same bending condition is greatly improved.

Example 2:

The difference between embodiment 2 and embodiment 1 is that the low refractive index part 4 is quartz glass with 2.0wt% ytterbium oxide, and aluminum ions can be doped to improve performance.

Example 3:

Fig. 2 is a schematic cross-sectional view of the optical fiber of Embodiment 3 of the invention. The difference between Embodiment 3 and Embodiment 1 is that the shape of the inner cladding region 6 is hexagonal, and the side length of the hexagon is 60 μm.

Example 4:

Fig. 3 is a schematic cross-sectional view of the optical fiber of Embodiment 4 of the invention. The difference between Embodiment 4 and Embodiment 1 is that the inner cladding region 6 of the refractive index anti-guiding multi-core optical fiber contains 8 refractive index anti-guiding cores. 2 and 14 sub-wavelength diameter cores 5 .

Claims (6)

1. A refractive index anti-guiding multi-core optical fiber, comprising a plurality of cores and a cladding region, characterized in that the cladding region comprises an inner cladding region (6) and an outer cladding region (7), in the A plurality of refractive index anti-guiding cores (2) and a plurality of sub-wavelength diameter cores (5) between the refractive index anti-guiding cores (2) are linearly arranged in the inner cladding region (6) ; The refractive index anti-guiding core (2) is made of two coaxial materials with a low refractive index (4) in the middle and a high refractive index (3) in the periphery, and the inner cladding region (6) The refractive index is smaller than the refractive index of the anti-guiding core (2) and the sub-wavelength diameter core (5), but greater than the refractive index of the outer cladding region (7); the inner cladding region (6) and the outer cladding region (7) ) are composed of solid materials with a uniform distribution of refractive index. 2. The refractive index anti-guiding multi-core fiber according to claim 1, characterized in that the core diameter of the refractive index anti-guiding fiber core (2) is micron order, and the sub-wavelength diameter fiber core (5) The core diameter is on the order of hundreds of nanometers, and the distance between the sub-wavelength diameter fiber core (5) and the refractive index anti-guiding fiber core (2) is on the order of wavelength. 3. The refractive index anti-guiding multi-core optical fiber according to claim 1, characterized in that the refractive index anti-guiding cores (2) are closely arranged with each other. 4. The refractive index anti-guiding multi-core fiber according to claim 1, characterized in that the shape of the inner cladding region (6) is rectangular or polygonal. 5. The refractive index anti-guiding multi-core fiber according to claim 1, characterized in that the low refractive index part (4) in the refractive index anti-guiding fiber core (2) is doped with rare earth elements neodymium, erbium, ytterbium At least one of thulium, lanthanum, and at least one of aluminum, phosphorus, and fluoride doped with quartz glass, silicate glass, phosphate glass, or tellurate glass. 6. The refractive index anti-guiding multi-core fiber according to claim 1, characterized in that the matrix material of the sub-wavelength diameter core (5), the inner cladding region (6) and the outer cladding region (7) is Quartz glass, silicate glass, phosphate glass, or tellurite glass.

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