Modeling of Tm, Ho:YAG and Tm, Ho:YLF 2- mum Lasers and Calculation of Extractable Energies

The development of a model for 2-mum laser operation in Tm, Ho:YAG and YLF crystals pumped in the near infrared is reported. This model, based on a simplified spectroscopic scheme, is fitted to a set of characterization experiments by means of three adjustable parameters. Results show that the excited-state populations are predicted with a relative accuracy of approximately 10% for a large range of pump levels. Using this model, we calculate the extractable energy on short-laser-pulse interactions for the two materials under different operation conditions. We study the sensitivity to pump duration and the optimization of dopant concentrations. We investigate the improvement of the extractable-energy efficiency with multiple-pulse operation. For double-pulse operation the improvement is approximately a factor of 1.5 and leads to overall extractable-energy efficiencies of 16% in YAG and 15% in YLF for an absorbed pump energy of 10 J cm(-3).