Theoretical Exploration Research Of Thulium-doped Fiber Lasers

During the second half of20th century, there are two periods that are very important stages in the development of fiber lasers. In1960s, the fiber laser was demonstrated by scientists later than lasers; the researchers designed the double cladding structure for the fiber instead of single cladding fiber. Then fiber lasers had a rapid development period, and applied in many fields. Comparing with traditional solider lasers, fiber lasers have large advantages of high efficiency, good beam quality, compact size, ease of integration and good heat dissipation. So fiber lasers are used in the fields of materials processing, medical treatment, target designation, laser ranging, etc. In this article, two main pumping methods are discussed in theory including the thulium-doped fiber lasers which operate at2μm and1.47μm. The wavelengths of two lasers belong to the wavelength range of human eye safety, and have good value of the application. The main work of my article is done as follows:1. First of all, the fundamental principles and knowledge of fiber lasers are introduced and discussed. The linear cavity structure classifications include two types whose resonators are composed by dichroscope and fiber Bragg grating, separately. Then the theory of annular resonator is discussed. The structure and theory of double cladding fiber is researched, and analysis the advantages of the structure of annular resonator. Two types of pumping including end-pump and side-pump are detailed and researched.2. According to the rate equations and transmission equations, we research and analysis the theory of the fiber laser pumped at793nm. The expressions are worked out including pump light and laser transmission in the optical fiber, the out power, the threshold power and slope efficiency by taking advantage of the way of analytical solution. Then, the distribution of pump light and laser in the optical fiber, the length of fiber, reflectivity of cavity mirrors, optical fiber loss, cross section of the fiber and the doping concentration are simulated using the simulation software(MATLAB). 3. At the same time, on the basis of existing theory, the Tm3+-doped fiber laser pumping at1064nm is researched further. Here the rate equations are different with the equations mentioned previously. When the boundary conditions are given, the theory simulation about pump and laser in the optical fiber and the influence of the out power and doping concentration are simulated by the way of Runge-Kutta using MATLAB.