Photonic bandgap fiber (PBGF) and frequency-shifted fiber laser

Abstract

The invention is applicable to the technical fields of optical fiber and fiber lasers, and provides photonic bandgap fiber (PBGF). The PBGF comprises a cladding layer and a fiber core wrapped in the cladding layer, wherein, the internal cladding layer is formed by a ring composed of large air holes, and the internal cladding layer contains germanium (Ge)-doped glass wires; and the fiber core contains a fluorine (F)-doped area with low refractive index. In the invention, slight refractive index subsidence is applied to the fiber core of the all-solid-state PBGF, which effectively enhances resonance coupling between a mode field and the Ge-doped glass wires in a 'loss zone' and further reduces the number of the Ge-doped glass wires in the cladding layer and absorption of the glass wires in the cladding layer on pump light.

Description

technical field [0001] The invention belongs to the technical field of optical fibers, and in particular relates to a photonic bandgap optical fiber and a frequency-shifting optical fiber laser. Background technique [0002] The research on "frequency-shifted fiber laser" based on photonic bandgap effect is a frontier research topic in the field of fiber laser. Generally, the output wavelength of Ytterbium-doped fiber laser is between 1000-1120nm, and it is difficult for people to obtain high-power "frequency-shifted" laser output of 976nm or 1120-1180nm. However, fiber lasers with the latter two wavelengths are very attractive, and their frequency doubling is a new technical way to generate blue and yellow lasers. In the research, it is found that even if the fiber grating pair is used to force the frequency selection, it is difficult to eliminate the parasitic laser light near 1060nm. In the final analysis, this is determined by the fluorescence gain spectrum of ytterbium...

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Problems solved by technology

High doping of ytterbium will correspondingly increase the refractive index of the fiber core and enhance the ability to confine the mode field. In turn, it is necessary to require the germanium-doped glass wire in the cladding to be closer to the fiber core, so that stronger resonant coupling occurs to form a "loss zone" to suppress strong gain region, which limits the mode field area from becoming large

2) The high refractive index germanium-doped glass wire contained in the fiber cladding will capture part of the pump light, resulting in a reduction in the light-to-light conversion efficiency. Therefore, in the actual optical fiber production, people expect to use as little glass wire as possible to provide the photonic bandgap effect

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