Ld-pumped Yb-doped Double-clad Fiber Laser

Great improvement has been achieved in high power fiber lasers with the breakthrough of clad pumping technique since the last period of 1980s. And it has become a focus of concern in the field of optoelectronics worldwide for their excellent performance and abroad of application. In this thesis, Yb~3+-doped Double Clad Fiber Lasers(Yb~3+-DCFLs) have been studied in experimentally and theoretically. The main subjects are as the following:1. Brief Review of the History, Development and Applications of Yb~3+-DCFLs. And it pointed out the significance of the research of double-clad fiber lasers.2. According to the characteristic of the energy level structure and spectrum of Yb , we gave the theoretical analyses about the choice of pump source .And we also analysis the influence of different inner clad shape on the absorptive efficiency of double clad fiber laser.3. The rate equations of theory Yb~3+-DCFL is constituted ,which include the effect of the distribution waster along the fiber with and Spontaneous emission . By using the rate equations and Rounge—Kutta way, output power and the threshold characteristics of DCFL are analyzed theoretically, such as the fiber length and cavity reflectivity are analyzed with a comprehensible model . It is found that there is an optimum fiber length in DCFL at a defined pump power, and output mirrors with low reflectivity is better for high gain fiber lasers. And It is found that the distribution waster along the fiber with and Spontaneous emission are effect the output power, we consider them.influence especially high power fiber lasers.The LD pumping scheme of Yb~3+-DCFLs is studied by using numerical calculation .It is shown that two-end pumping is the best choice for high power fiber lasers for the reason that it can reduce the power density on the input fiber end and can get a more uniform gain profile as well as power...