High-power Double-clad Fiber Laser Theory And Experimental Research

Because double-clad fiber lasers possess both the good qualities of tradition solid lasers and fiber lasers, they have great potential in research and applied fields. In the paper, we focus on theoretical and experimental research on Yb3+-doped double-clad fiber lasers. Main works are abstracted as follows:1. Theoretical research on double-clad fiber lasers. Through the velocity rate equation, we got the explicit expressions of the output characteristics and the cavity parameters of the Yb3+-doped double-clad fiber lasers(YDFL). The distribution of the power of pump laser and the relation between the output power and the pump power were analyzed by the method of numerical simulation. We further studied the influence to the maximum output power, threshold power, slope efficiency and output wavelength by the wavelength of pump and signal laser, fiber length and reflectance of both the front and back cavity mirrors of the Yb3+-doped double-clad fiber laser. In super high power fiber lasers, thermo effects would not be neglected. Based on the modal of steady state temperature distributions equation, the temperature distribution in double-clad fiber is numerically simulated. The results show that fiber length, cooling condition and radio of cross section inner-clad of double-clad fiber have obvious effect on the fiber temperature.2. Using high power pump source and eight-square inner-cladding Yb3+-doped double-clad fiber, we realized a high power YDFL with a maximum output 38 W and center wavelength 1091 nm. Using D-shaped inner-clad fiber made in China, we realized a high power of 32.5 W and the slope-efficiency is 70.5%, the center wavelength is 1.083μm. Based on the principle of Fabry-Perot interferometer, we realize a multi-wavelength YDFL with stabilization output. The maximum ten-wavelength can be achived at the same time with a output power of 1.5 W.3. Designed and achieved a high power YDFL , which all of the components were made in China. The output power is 12.73 W when the absorbed pump power is 18.63 W with a slope-efficiency of 76.9%. The light-light conversion efficiency is 45%. The output of the laser is very stable, and the fluctuation of output power is less than 0.5% under long-time high-power operation.4.Observations are presented on the self-pulsing behaviour of YDFL. Explained the modulated phenomena in output pulse by use of horizontal mode beat-frequency. The experiments show that under especially condition the laser can achieve stable self-pulsing output. We also discussed the method of how to avoid self-pulsing behaviour in continuum wavelength fiber laser.5. Developed the technology of fabricating fiber Bragg gratings (FBG) in Yb3+-dopded...