Study On Devices Of Yb～(3+)-Doped Silicon Fibers

Ytterbium (Yb)-doped silica fibers have a broad-gain bandwidth (850~1050nm), excellent power conversion efficiency, and a broad-absorption bandwidth (900~1200nm). Their ability to provide amplification over the very broad wavelength range from ~975nm to ~1200nm is expected to generate increasing interest in the near future. They offer an almost ideal gain medium for the fiber lasers and fiber amplifiers that work at the wavelength around 1μm. Using double-clad fibers, an efficient coupling of a high-power pump source into a single-mode fiber core can be achieved. High-power Yb-doped fiber lasers have caused particular interest as a reliable, efficient and compact, low cost source for a variety of applications in industry, printers, free-space communication, national defense and so on. The dissertation focuses on the Yb-doped double-clad fiber lasers, the fiber Bragg gratings in double-clad fiber, the fiber lasers based on double-clad fiber grating and pumping methods. The research works in detail are shown as follows:1. We firstly summarize the development of Yb-doped fiber lasers, pumping methods and the applications of high-power fiber lasers.2. Considering the scattering loss, we deduce the relationships between laser performances of Yb-doped double-clad fiber laser and parameters of laser cavity from the steady state rate equations, numerically analysis the changes of laser performances, such as laser power with the parameters of laser cavity, including output mirror reflectivity, optimum length of double clad fiber. We analysis the characters of double-clad fiber laser with mode selected based on fiber Bragg grating in double-clad fiber. These results are very important when optimizing the structure of a double-clad fiber laser.3. With the phase-mask method, we make a fiber Bragg grating in a few-mode fiber with the peaks at the wavelength around 1060nm. We have studied the temperature dependant characteristics of few-mode fiber Bragg gratings theoretical and experimentally. The experimental result of fiber laser based on the few-mode fiber Bragg grating is presented.4. We have studied the fiber Bragg gratings formed in double-clad fibers, with and without Hydrogen loaded, via the phase-mask method. A phase-shifted Moiréfiber Bragg grating is also fabricated in double-clad fiber.5. Several traditional pumping methods are considered. How to improve the pump efficiency in a double-clad fiber laser is studied and the light propagation characteristics in the circular and rectangular are analyzed by using ray optics. Two...