High-efficiency single-frequency thulium-doped fiber laser based on in-band pumping

Abstract

The invention discloses a high-efficiency single-frequency thulium-doped fiber laser based on in-band pumping. Laser with the wavelength of 1650 nm is adopted as a pumping thulium-doped fiber laser, the pumping wavelength corresponds to the vicinity of the peak value of a pumping absorption spectrum in a thulium-doped fiber ribbon, the high absorption cross section is achieved, the small quantum loss is achieved, the efficiency of the laser can be greatly improved, and the noise and line width characteristics of the laser are improved. High-efficiency and high-power 1650 nm laser output can be obtained in a stimulated Raman scattering mode, and a foundation is laid for obtaining a high-power single-frequency fiber laser.

Description

technical field [0001] The invention relates to the field of fiber lasers, in particular to a high-efficiency single-frequency thulium-doped fiber laser based on in-band pumping, and in particular to a new pumping method for the thulium-doped fiber laser. Background technique [0002] Thulium-doped fiber laser is an effective technical means to obtain 2μm fiber laser. In recent years, the research on thulium-doped fiber laser has been deepening. At present, the mainstream fiber resonator structure is DBR (distributed Bragg reflection, distributeBragg reflection) short-cavity structure. Due to its short active fiber length (<2cm), it is difficult to obtain high-efficiency laser output. In the past 10 years, the mainstream method is to use highly doped rare earth doped soft glass fiber as the gain medium in the resonator to improve the output efficiency of the laser. Thulium-doped fiber lasers based on germanate and silicate glass substrates have been reported one after an...

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Problems solved by technology

793nm corresponds to 3 h 6 → 3 h 4 The absorption band of the energy level transition is the pumping wavelength of the most mainstream thulium-doped fiber laser. The pumping method is a three-level structure. Reaching 200% can greatly improve the efficiency of the laser, but when the 793nm laser is used for pumping, it is seriously affected by the concentration cluster effect, and it is difficult to achieve the ideal 200% quantum efficiency, and there is currently no high-power 793nm single-mode laser Diodes can be used as laser pumping sources, so this pumping method is greatly limited in practical applications; 1210nm corresponds to 3 h 6 → 3 h 5 Although the absorption band peak of the energy level transition has almost the same absorption cross section as 793nm, due to the lack of cross relaxation process, there is a large quantum deficit in the pumping process, which makes it difficult to greatly improve the laser efficiency; 1570nm corresponds to 3 h 6 → 3 f 4 Transition stimulated absorption band, the pumping method is a two-level structure, which belongs to the in-band pumping. In the reported work, the efficiency of the pumping method is low, mainly due to the low performance of the thulium-doped fiber on the 1570nm laser. Absorption cross section

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