Resonant sum-frequency generation

A theoretical and numerical analysis of doubly or singly resonant sum-frequency generation of two laser beams in an external cavity is presented. The plane-wave equations for three-wave mixing-as applied to Gaussian beams using a Boyd-Kleinman overlap integral-are found to give excellent agreement with 3-D numerical simulations. In many regimes of practical interest, the present theory is also in excellent agreement with earlier work of Kaneda and Kubota. In particular, the generation of 589-nm CW sodium-resonance radiation in lithium triborate using two Nd:YAG lasers is considered. Matching the photon flux of the two laser beams is generally optimal. A suitable choice of input-coupler reflectivities (decreasing as the flux level increases) results in high-efficiency conversion with acceptable tolerance to input flux imbalance.