Tm³⁺ Doped Double-clad Fiber Laser Theoretical And Experimental Research

Emission spectra of Tm3+-doped fiber laser which contains two atmospheric windows and a strong water absorption peak covers from 1.5μm to 2.2μm. Because the wavelength is safe to man's eyes, it is being applied in many areas such as laser medicine, long-distance detective systems, laser radar, and military fields, and it is a new research focus in the fiber laser field.In this paper, Tm3+-doped double clad fiber laser is researched in theory and experiment. The main contents are summarized as follows:1 The basic theory of Thulium-doped fiber laser is introduced, and the key technologies of double-clad fiber lasers are introduced and elaborated. For the energy level structure of thulium, we researched the characteristic of it and analyzed the absorption spectrum, present three kinds of pump scheme of the Tm3+-doped fiber laser:3H6â†'3F4,3H6â†'3H5,3H6â†'3H4,and analysis the pumping process. The absorption cross section of 3H4 at the pump wavelength is larger than the others, the pumping scheme of 3H6â†'3F4 is hard to reverse the particle for it is two energy system, the energy 3H5 has excite state absorption, than, conclude that the pumping scheme 3H6â†'3H4 is more excellent.2. In theory, based on the rate equations, an analytical model of Tm3+-doped double clad fiber laser is developed, and the analytical expressions of output power and threshold pump power of fiber laser are obtained. The distribution and transmission of the fiber fundamental mode are simulated by the COMSOL software. The power distribution of pumping light and signal light in fiber, fiber length, rear cavity mirror reflectivity, threshold power, doping concentration and pump geometry which can influence the characteristic of the fiber laser are deeply investigated in the MATLAB simulation environment.3. In experiment, comparing the technology of hand-grinding with machine-polishing, end face of solid double-clad fiber and photonic crystal fiber are primarily grinded with the details of experimental operation technique being improved. The Tm3+-doped fiber laser with Fabry-Perot cavity is carried out, and the maximum output power obtained is 2.89W, and the slope efficiency is up to 27.5%, and the instability is 3.7%. The experimental results and some problems are reasonably analyzed, and then some ideas and suggestions are presented.