Cylindrical KTiOPO_4 crystal for enhanced angular tunability of phase-matched optical parametric oscillators

We demonstrate what is to our knowledge the first optical parametric oscillator (OPO) based on a cylindrical phase-matched nonlinear crystal. Experiments are performed with an uncoated KTiOPO(4) crystal cut as a cylinder with a diameter of 21.2 mm and a thickness of 5 mm. We achieve 20.5-internal-degree angular tuning in a 1064-nm-pumped type III OPO, which would correspond to ~36 degrees external angular rotation for a parallelepipedal crystal. The goals of using such a device are to narrow the spectral width of the output and to enhance the spatial quality of the generated beams in widely tunable OPO's.