Theoretical And Experimental Study Of The Ytterbium-doped Double-clad Fiber Laser

Prominent improvement has been achieved in high power fiber lasers with the breakthrough of clad pumping technique since the last period of 1980s. And fiber laser has become a focus of concern in the field of optoelectronics worldwide for their excellent performance and abroad of application. Yb³⁺-doped fiber laser has been attracted greatly because of simple energy structure, no excited state absorption, and wide tunable range, and widely used in optical communication, aviation and spaceflight, sensing, measuring and industrial fabrication for their compact structures.In this paper, Yb³⁺-doped double clad fiber laser is studied in theory and experiment. The main subiects are list as follows:Brief review of the history, development and applications of Yb³⁺-doped double clad Fiber Lasers are introduced.Based on rate equations and transmission equations, the theory model of linear cavity Yb³⁺-doped double clad fiber lasers is developed. The effects of fiber length, loss and reflectivity of both the front and back cavity mirrors of the double-clad YDFL on laser output power, threshold pump power, slope efficiency and output wavelength are discussed. The results provide theoretical guidance for design and fabrication of fiber laser.Experimental study of Yb³⁺-doped Double Clad Fiber Lasers with Fabry-Perot laser cavity waspresented: the end of the double-clad fiber was polished by a lapping plate and excellent optical surface was obtained. According to the parameters of double-clad fiber and LD pump source, we developed a pump coupling system made up of lenses, and the coupling efficiency was up to 33%. The single transverse mode double clad fiber laser with output power of 4.75W and slope efficiency of 76% is achieved at 6.35W pump power.By decreasing the reflectivity of input mirror and separating the distance between the mirror and fiber end, a Fabry-Perot filter is formed. A novel narrow linewidth fiber laser with 1.34 W output power and 25% slope efficiency is obtained by adjusting the filter.