Modeling of Tm,Ho : YAG and Tm,Ho : YLF 2-mu m lasers and calculation of extractable energies

The development of a model for 2-mu m laser operation in Tm,Ho:YAG and YLF crystals pumped in the near infrared is reported. This model, based on a si mplified spectroscopic scheme, is fitted to a set of characterization exper iments by means of three adjustable parameters. Results show that the excit ed-state populations are predicted with a relative accuracy of approximatel y 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 dura tion and the optimization of dopant concentrations. We investigate the impr ovement 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). (C) 1998 Optical Socie ty of America. OCIS codes: 140.3580, 160.5690, 010.3640, 140.0140.