Abstract

High efficiency and high output energy parametric devices, such as optical parametric generators (OPG’s) and optical parametric oscillators (OPO’s) typically employ supergaussian non diffraction-limited pumping beams derived from nanosecond Q-switched Nd:YAG lasers. The parametric beams generated with such pumping in OPG’s and OPO’s have M² value substantially exceeding that of the pump beam, which strongly limits achievable brightness and usefulness of the generated power. The parametric beam quality approaching that of the pump in such devices is obtainable only close to the oscillation threshold. In this work we report on the experimental investigation of the spatial and temporal coherence of the near-field distribution generated in OPG and OPO and its effects on the far-field divergence and parametric beam brightness. Moreover, we demonstrate, that both the near field spatial and temporal coherence as well as the parametric beam brightness can be strongly enhanced by using Bessel pump.

© 2001 EPS