Characteristics and Laser Performance of Yb3+-Doped Silica Large Mode Area Fibers Prepared by Sol-Gel Method

Large-size 0.1 Yb2O3-1.0 Al2O3-98.9 SiO2 (mol%) core glass was prepared by the sol-gel method. Its optical properties were evaluated. Both large mode area double cladding fiber (LMA DCF) with core diameter of 48 mu m and large mode area photonic crystal fiber (LMA PCF) with core diameter of 90 mu m were prepared from this core glass. Transmission loss at 1200 nm is 0.41 dB/m. Refractive index fluctuation is less than 2 x 10(-4). Pumped by 976 nm laser diode LD pigtailed with silica fiber (NA 0.22), the slope efficiency of 54% and "light-to-light" conversion efficiency of 51% were realized in large mode area double cladding fiber, and 81 W laser power with a slope efficiency of 70.8% was achieved in the corresponding large mode area photonic crystal fiber.