Investigation Of 2μm Tm³⁺-Doped Double-Clad Fiber Lasers

Cladding-pumped Thulium-doped double-clad fiber lasers which use the technology of cladding-pump to pump gain fiber can obtain the laser transition between 3F4 and 3H6 at approximately 2μm.The laser near 2μm operates at eye-safe region, and the laser has a great use in industry, medicine and military, it even could be used as the pump source of 3~5μm OPO. Therefore it is valuable to research Tm3+-doped fiber laser operating at 2μm.The research of this paper starts from the energy level structure of Tm3+, then we analyzed the transition of 3H6â†'3H4 and the process of laser output including a detailed numerical analysis. The forward and backward distributions of pump power and signal power, the dependence of the fiber length and the transmission loss are also numerically modeled. After that we designed the couple system of the laser system.Based on all of these theories, we determine the program of our experiment. We purchased the equipments related to the experiment, including pump sources, aspheric lens, dichroic mirror, etc. We set up the fiber optic test platform and the fiber laser platform. We tested the absorption coefficient of the fiber and determined the best length of fiber through experiment. Finally we realized 7.4W CW output power with central wavelength of 1909nm,the threshold of the system is about 2.5W and the slope efficiency is 35.8%.At last we improved the experimental program that we wrote the FBG at the end of the gain fiber. It is used to increase the effect of the resonator and execute frequency selection.