It is shown that for pulsed optical parametric oscillators there is an
optimum pump-pulse duration at which the threshold fluence is a minim
um. The dependence of the threshold fluence on pump laser pulse durati
on is found to be substantial for lossy narrowband optical parametric
oscillators. The pulse energy requirement for the pump laser may be su
bstantially lowered by operating it at a pulse duration close to the o
ptimum. (C) 1998 Elsevier Science Ltd.