Air hole square array fiber core annular doping four-core photonic crystal fiber

Abstract

The invention relates to an air hole square array fiber core annular doping four-core photonic crystal fiber, which comprises a fiber cladding and fiber cores, wherein the fiber cladding is formed by distributing a plurality of layers of air hole square arrays; the fiber core is formed by four groups of units lack of air holes; and the four fiber cores are symmetrically distributed at diagonal lines of four quadrants. Each fiber cores comprises an inner core and a doping annular area, wherein the inner core and the fiber cladding are made of quartz materials, and the doping annular area wrapped outside the inner core is made of quartz doped with an oxide capable of increasing a refractive index, so that the refractive index of the doping annular area is a little higher than that of the fiber core. With the adoption of the fiber core annular doping four-core structure, the mode area can be efficiently increased, and the nonlinear effect can be reduced. The fiber core annular doping can form a flat mode field, thereby efficiently reducing the thermal damage effects of the fiber. The fiber cladding is formed by distributing the plurality of layers of air hole square arrays, so that the ultralow limit loss can be realized, and the energy loss can be greatly reduced in the transmitting process.

Description

technical field [0001] The invention relates to a circularly doped four-core photonic crystal fiber with a square array of air holes, in particular to a photonic crystal fiber with a flat-top mode field, a large mode area and ultra-low confinement loss, and belongs to the field of optical fiber technology. Background technique [0002] Due to its advantages in efficiency, heat dissipation and beam quality, high-power fiber lasers have broad application prospects in the fields of industrial processing, medical treatment and national defense. However, nonlinear effects such as Raman scattering, Brillouin scattering, and four-wave mixing limit the further improvement of the output power of high-efficiency fiber lasers. There is a great relationship between the nonlinear effect and the light intensity. By increasing the mode area of ​​the fiber, the light intensity can be effectively reduced, thereby inhibiting the nonlinear effect. Photonic crystal fiber (PCF), also known as m...

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Problems solved by technology

[0003] Studies have shown that doping the silica core of photonic crystal fiber, doping ZrO 2 、TiO 2 、Al 2 o 3 、GeO 2 ,P 2 o 5 Such materials can increase the refractive index of quartz glass (high doping), doping B 2 o 3 , F and other raw materials can reduce the refractive index of silica glass (low doping), and the doped fiber can obtain a larger mode area, but at present this doping technology is only limited to single-core fiber, which limits the mode area. Further improve

If a multi-core fiber is used, although a larger mode field area can be obtained compared with a single-core fiber, from the perspective of each fiber core, the output beam is a traditional Gaussian beam. When the pump light power is large, It is easy to damage the fiber end face

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