Theory And Experiment Study On High-power Ytterbium-doped Double-clad Fiber Lasers

This paper will both theoretical and experimental aspects of high-power ytterbium-doped double-clad fiber plasma research. The main work includes the following sections.1. Fiber laser devices introduction: At the beginning, the first chapter introduced the progress of fiber laser development and systemically analyzed its characteristics and category, including its advantages over other types of laser devices and the status and prospect of its applications around the world.2.Theoretical analysis of the fundamental principles and structure of fiber laser devices: Later in the first chapter, the principles and structure of three kinds of resonator: F-P cavity,fiber-optic ring resonator, the fiber loop reflector were analyzed in detail, together with the energy level structure of the fiber laser's gain medium.3. In-depth research on double-clad fiber lasers: the second chapter studied four different structures of double-clad fiber lasers: circular structure of the inner cladding,offset core-type structure of the inner cladding,rectangular inner cladding structure,quasi-circular inner cladding structure and calculated the distribution of the pump-light in double-clad fiber of them respectively. Introduced fiber coupling technology from the following four aspects: the selection of fiber and processing of fiber end face, the condition for fiber laser coupling,how lens aberration affects the efficiency of coupling and the decrease of efficiency of coupling caused by the inaccuracy of beam and fiber.4.Theoretical research on ytterbium -doped double-clad fiber lasers: Doped fiber is a special kind of fiber with initiative characteristic, which consists of dopant and fiber matrix as host。Thus, its characteristics of laser, optical augment, mag-optical and so on closely depend on the kind, characteristic, density and distribution of the rare earth ion dopant. The third chapter first researched the characteristic of ytterbium-doped double-clad fiber, from discussing the spectrum characteristic of rare earth ion, especially Ion's third and forth level electronic structure, which provided the theoretical support for the experiment of high-power fiber laser in chapter four. In the end the main advantages of fiber laser, which uses ytterbium-doped double-clad active fiber as its main material, are introduced.5.Experiment of fiber laser: Chapter four is the body part of the paper, which researched and analyzed the phenomena raised during the experiment of fiber laser. First, the three main ways of pumping for fiber laser were introduced and the proper one was chosen according to the requirement of the experiment. In the end, the critical techniques in the experiment, such as the connection between fibers and the processing of fiber face were introduced. The theory of fiber laser devices has become quite complete and technologies in foreign countries are becoming mature day by day. However, the research on this area in our country is still in the beginning step. I sincerely hope that more researchers will devote themselves into this area to promote the progress the theoretical and experimental research of fiber laser in China.