Ho:Ho upconversion rates are predicted with a quantum-mechanical model and measured with a Q-switched laser to directly excite the Ho manifold. If Ho:Ho upconversion is low compared with spontaneous decay, Q-switched, Ho-only lasers can store energy efficiently over long time intervals. In this case, Ho-only lasers, when pumped by long-pulse-length Tm-only lasers, have great potential. Ho-only lasers have proven to be efficient, and, when long pump pulses are used, fewer laser diodes are required. To assess the Ho laser potential, Ho:Ho upconversion parameters are calculated and measured for several Ho laser materials including Ho:YAG and Ho:YLF. The effects of both nonuniform pump energy deposition and diffusion of the excited Ho distribution are analyzed.
© 2003 Optical Society of America