Beam-quality studies of nanosecond singly resonant optical parametric oscillators

A numerical model for a singly resonant, nondegenerate optical parametric o scillator, which includes diffraction and idler absorption, has been develo ped. This model requires just one equation for the resonated signal field t o be numerically integrated, while the pump and idler fields are reconstruc ted from their analytic solutions and the dynamics of the signal field, Typ ical results from our simulations are, for example, output intensities and threshold fluencies, which can be compared with those obtained from experim ents. Spatial beam quality of output beams produced by our model is evaluat ed via the M-2 factor, We present results from the simulation which are con sistent with experimental evidence, particularly in reference to the impact of idler absorption.