HIGH-POWER DOUBLE-CLAD FIBER LASERS

Rare-earth doped, laser-diode-pumped, single-mode double-clad fiber lasers are studied in detail, experimentally and theoretically, with particular attention to scaling properties to higher output powers. Gain saturation, spontaneous emission, fiber propagation loss and optimum output coupler are considered in oscillator design and laser performance. Thermal properties are investigated, including the thermal fracture limit, the decrease of quantum efficiency with increasing pump power through the temperature dependence of multi-phonon decay and ion-ion energy transfer, and thermal lensing. Self-focusing and Raman effects are briefly considered. It is shown that output powers in the tens of watts range are readily feasible with available double-clad fiber lasers.