A large mode field double-clad ytterbium-doped fiber

Abstract

The invention discloses a large-mode-field double-clad ytterbium-doped optical fiber, which comprises a fiber core, a quartz inner cladding that wraps around the outer periphery of the fiber core sequentially from the inside to the outside, a low-refractive index outer cladding and an outer coating, and the quartz inner cladding is close to the fiber core. The inner surface of the core is provided with a concave area of ​​refractive index. The core contains ytterbium. Along the diameter direction of the core, the concentration of ytterbium is distributed in a trapezoidal or parabolic shape from the inside to the outside. The diameter of the ytterbium doped area is smaller than or equal to that of the core. diameter. The present invention improves the refractive index distribution and doping distribution of the optical fiber without changing the mechanical properties of the optical fiber and without increasing the manufacturing cost and difficulty of the optical fiber. The combined action of the two can maintain the field area of ​​the fundamental mode, and combine the triangular and step-shaped The complex refractive index design of the fiber core is designed to adjust the balance between the effective mode field area of ​​the fundamental mode and the extraction efficiency of the fundamental mode by changing the composite shape, and concentrate the light field energy to the center of the fiber core, so the extraction efficiency of the fundamental mode can be improved, and the obtained High beam quality laser output, improved beam quality.

Description

technical field [0001] The invention relates to the field of optical fiber technology, in particular to a large mode field double-clad ytterbium-doped optical fiber. Background technique [0002] If the fiber core is doped with rare earth elements, when proper pump light is injected into the fiber, the outer electrons of the rare earth elements will absorb the energy of photons and jump to a higher energy level. When the number of particles in the excited state is reversed, the signal light passing through the core induces stimulated emission and is amplified. In fiber lasers, the resonant cavity structure makes the stimulated radiation light form a laser oscillation output with high beam quality and high power density. Different optical fiber material systems combined with different rare earth element doping can radiate light of various wavelengths under the excitation of corresponding wavelengths of light, and can cover the spectral range from ultraviolet to infrared. Fi...

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Problems solved by technology

[0010] The technical problem to be solved by the present invention is that it is difficult to realize the quasi-single-mode operation of the fiber on the basis of the large core diameter and large mode field structure in the current ytterbium-doped silica fiber

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