Highly Tunable Low-Threshold Optical Parametric Oscillation in Radially Poled Whispering Gallery Resonators

Whispering-gallery resonators (WGR's), based on total internal reflection, possess high quality factors in a broad spectral range. Thus, nonlinear-optical processes in such cavities are ideally suited for the generation of broadband or tunable electromagnetic radiation. Experimentally and theoretically, we investigate the tunability of optical parametric oscillation in a radially structured WGR made of lithium niobate. With a 1: 04 mu m pump wave, the signal and idler waves are tuned from 1.78 to 2: 5 mu m-including the point of degeneracy-by varying the temperature between 20 and 62 degrees C. Aweak off centering of the radial domain structure extends considerably the tuning capabilities. The oscillation threshold lies in the mW-power range.