Active element added-optical fiber, resonator, and fiber laser device

Abstract

A core (11) includes a first region (11a) and a second region (11b). The first region (11a) is a region of a radius ra from a central axis and has an active element that is excited by excitation light added thereto. The second region (11b) is a region surrounding the first region (11a) without a gap and extending to an outer peripheral surface of the core (11), and does not have the active element added thereto. When the radius of the core (11) is d, 0.1d<ra<d, and when the distance from the central axis in a radius direction of the core (11) is r, an average value of the concentration of the active element in a region where 0<=r<=0.1d is higher than an average value of the concentration of the active element in a region where 0.1d<r<=ra. In a region where 0.2d<r<=0.9d, there is at least one maximum value position at which the refractive index is higher than an average value of refractive index in a region where 0<=r<=0.9d and is at a maximum.

Description

technical field [0001] The invention relates to an active element-added optical fiber, a resonator, and a fiber laser device capable of suppressing the deterioration of beam quality. Background technique [0002] Fiber laser devices are used in various fields such as laser processing and medical fields because of their excellent light-gathering properties, high power density, and ability to obtain light with small spots. In such fiber laser devices, output light is increasing in output. However, if the optical power density in the fiber increases, conversion of the optical wavelength by stimulated Raman scattering will easily occur, and light of an unintended wavelength will be emitted. In this case, the light reflected by the object to be processed returns to the fiber laser device again to be amplified, and the amplification of the light of the designed wavelength to be amplified becomes unstable and the output becomes unstable. [0003] As a method of suppressing stimul...

AI Technical Summary

Problems solved by technology

However, if the optical power density in the fiber increases, wavelength conversion of light due to stimulated Raman scattering will easily occur, and light of non-target wavelengths will be emitted.

In this case, the light reflected by the object to be processed will return to the fiber laser device again and be amplified, resulting in instability of the amplification of the light of the wavelength that should be amplified by design, resulting in unstable output

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