Improving the beam quality of nanosecond optical parametric oscillators

摘要

We show by computer simulation that high beam quality can be achieved in high energy, nanosecond optical parametric oscillators by using image-rotating resonators. Lateral walk off between the signal and idler beams in the nonlinear crystal creates correlations across the beams in the walk off direction, or equivalently, a restricted acceptance angle. This tends to improve beam quality in the walk off plane. We show that image rotation or reflection can be used to improve beam quality in both planes. The lateral walk off can be due to birefringent walk off in type II mixing or due to noncollinear mixing in type I or type II mixing.