Triple-clad silica fiber with inner cladding doped with alkali metal

Abstract

The invention discloses an inner cladding alkali metal doped three-cladding quartz optical fiber, which consists of a fiber core, an inner cladding and an outer cladding, and is characterized in thatthe inner cladding is made of alkali metal oxide doped quartz glass, and the refractive index of the inner cladding is (0-50)*10<-3> higher than that of pure quartz. The triple-cladding silica fiber with the inner cladding doped with the alkali metal can effectively improve the refractive index of the inner cladding, and is low in doping difficulty and cost.

Description

technical field [0001] The invention relates to the field of rare earth-doped optical fiber and laser technology, in particular to a triple-clad silica optical fiber whose inner cladding is doped with alkali metal. Background technique [0002] Rare earth ion-doped fiber lasers are widely used in laser processing, military and other fields due to their compact and stable structure, good heat dissipation, and excellent beam quality. [0003] The traditional rare earth doped optical fiber structure includes a rare earth doped glass core, a glass inner cladding, a first outer cladding made of a low refractive index organic resin and a second outer cladding made of a high refractive index organic resin. The main function of the rare earth-doped glass core is to realize laser output, and one of the main functions of the glass inner cladding and the first outer cladding is to increase the NA (NA~0.46) of the inner cladding to form a waveguide structure for pumping light, which is ...

AI Technical Summary

Problems solved by technology

At present, low-refractive-index fluorine-doped quartz tubes are generally used instead of traditional low-refractive-index organic resins as the first outer cladding of optical fibers to make triple-clad optical fibers. However, due to the limited fluorine-doping ability of quartz glass, its refractive index decreases limited range

At present, the maximum NA of the inner cladding of the triple-clad optical fiber is ~0.22, which is only half of the inner cladding of the traditional triple-clad optical fiber (with low refractive index organic resin as the outer cladding), which reduces the NA to a certain extent. The coupling efficiency of the pump source causes a loss of pump power, which affects the slope efficiency of the fiber laser output

[0005] The Chinese patent with the publication number CN107065066B proposes a multi-clad silica optical fiber structure, in which low-refractive-index quartz glass doped with fluorine, boron, etc. is used to replace the low-refractive index organic resin, thereby improving the thermal stability of the optical fiber. Elements such as yttrium, lanthanum, aluminum, and germanium increase the refractive index of the inner cladding, thereby increasing the NA of the inner cladding, but high-concentration doping of elements such as yttrium, lanthanum, and aluminum is difficult, and the cost of germanium doping is high

[0006] Literature SPIE, 2007, volume 6453, 645308-1 proposed a triple-clad structure with germanium-doped quartz glass as the inner cladding and pure quartz as the first outer cladding. This structure is limited by the refractive index of germanium-doped quartz glass. The NA of the inner cladding is less than 0.15, which cannot meet the NA requirements of high-power pump sources, and it is difficult to achieve high-power output

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