Ytterbium doped fiber laser using specific wavelength band pumping

Abstract

By adopting the laser provided by the invention, when the same optical fiber laser is adopted, the higher light-to-light conversion efficiency than the existing 915nm, 940nm, 976nm and other conventional pumping modes can be realized, the quantum loss is smaller, and the SRS threshold value of the laser provided by the invention is higher than the SRS threshold value of the existing 1018nm pumpingmode. A TMI threshold value higher than that of an existing conventional pumping mode can be achieved. Through central wavelength optimization, a higher TMI threshold is obtained compared with a 976nm pumping mode, a higher SRS threshold is obtained compared with a 915 nm pumping mode, a 940 nm pumping mode and a 976 nm pumping mode, and the laser output power under the current pumping mode is greatly improved.

Description

technical field [0001] The invention belongs to the field of fiber lasers, in particular to an ytterbium-doped fiber laser pumped with a specific wavelength band. Background technique [0002] As a representative of the new generation of lasers, fiber lasers have the advantages of compact structure, high conversion efficiency, good beam quality, and convenient thermal management. In recent years, they have achieved rapid development and application in the fields of industrial manufacturing and scientific research. In the process of light conversion, the gain medium (gain fiber) of the fiber laser achieves the population inversion of the upper energy level by absorbing the pump light, and realizes the output and amplification of the signal laser by means of stimulated emission. The difference in energy between the absorbed and emitted photons determines the quantum deficit of the fiber laser, and the energy of these losses is dissipated in the fiber as heat. According to the...

AI Technical Summary

Problems solved by technology

In the development process of fiber lasers, under the same fiber parameters, due to the low absorption coefficient of ytterbium-doped fiber to 915nm and 940nm bands (generally, the absorption coefficient of fiber near 915nm is about 1 / 3 of that near 976nm, and at 940nm The absorption coefficient near 976nm is about 1 / 4 of that near 976nm), so that when 915nm and 940nm LD pumped fiber lasers are used, the length of the gain fiber required is greater than that of 976nm LD pumped, resulting in a lower SRS threshold of the fiber laser and affecting Improvement of laser power; on the other hand, for the 1018nm fiber laser pumping method, under the same fiber core size, since the absorption coefficient of ytterbium-doped fiber at 1018nm is 1 / 6 or 1 / 6 of that of 915nm / 976nm band LD About 1 / 18, the required gain fiber length is longer than that of 915nm and 940nm pumps, and the SRS threshold is also lower

In addition, in the ytterbium-doped fiber laser, the TMI effect is proportional to the heat per unit length of the gain fiber. When 976nm LD is used as the pump source of the ytterbium-doped fiber, the absorption coefficient of the gain fiber at 976nm is 915nm and 940nm The band absorption coefficient is about 3 to 4 times, which makes the heat load per unit length of the gain fiber higher than that of 915nm, resulting in a lower TMI threshold of the 976nm pumped fiber laser than that of the 915nm pumped fiber laser

Therefore, in the current pumping scheme, 1018nm cascade pumping, 915nm / 940nm LD pumping fiber lasers are mainly limited by the SRS effect; 976nm LD pumping fiber lasers are mainly limited by the TMI effect, resulting in fiber It is difficult to further increase the laser power

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