Optimization of the cavity geometry in tunable optical parametric oscillators based on cylindrical crystals

Summary form only given. Optical parametric oscillators based on a cylindrical crystal have been realized recently, following the set-up where the cylinder axis is orthogonal to the cavity optical axis and to the plane containing the useful phase-matching directions. The interacting beams always propagate at normal incidence, leading to a broad angular tunability. The present study is devoted to the beam quality of the emitted signal. We demonstrate that the geometry of the KTP crystal is responsible for a spatial filtering effect which can result in a low M/sup 2/, independent on the spectral tuning of the OPO. We investigate the variation of the beam quality with respect to the different geometrical parameters: cavity length and radius of curvature of the mirrors, crystal diameter, pump beam waist size, and spectral range of the generated signal. These calculations, based on a simple gaussian beam model, allow us to define the most suitable operating conditions corresponding to a good and constant beam quality over a maximum spectral tuning.