Assessment of broad usability of a simple analytic model for passively Q-switched lasers with Cr:YAG saturable absorbers

Analytic approximations for key parameters of passively Q-switched (PQS) lasers, such as pulse energy and duration, were developed and widely tested in particular for microchip lasers with semiconductor saturable absorbers. However, the same approach can be readily extended to PQS lasers using Cr:YAG as the saturable absorber, including excited-state absorption (ESA) in the model. ESA causes a reduction of pulse energy and an increase in pulse duration. Interestingly, performances of many previously reported PQS lasers using Cr:YAG, from microchips to more powerful multi-millijoule lasers, are correctly predicted by this simple model. Unlike energy estimation, which is intrinsically robust, pulse width requires a more careful evaluation of the influence of the ratio (total linear loss)/(saturable loss) as a correction of the asymptotic result.