Skip to Main Content
We investigate theoretically and experimentally the interplay between cavity and double-refraction in continuous-wave optical parametric oscillators. We show that very basic geometrical effects can prevent transverse wavevector matching for the TEM00 modes, and thus increase the threshold and change dramatically the beam structures when using a resonant (or double-pass) pump. We extend the work of Boyd and Kleinman to take these cavity-induced mismatches into account, and test experimentally the theoretical results using a cw type II KTP OPO. The transverse wavevector mismatch leads to the appearance of transverse modes with increasing order (up to TEM40-0) and surprisingly induces structures that are different on signal and idler. The theory is able to predict quantitatively all selected transverse modes, and allows a simple interpretation in transverse Fourier space.