Theoretical treatment, simulation, and experiments of doubly resonant sum-frequency mixing in an external resonator

We describe the theoretical treatment of the doubly resonant sum-frequency mixing in an external resonator. The nonlinear conversion efficiency is increased by the resonantly enhanced circulating powers at both wavelengths. The model predicts the circulating powers in the resonator at two input wavelengths: the powers that are reflected off the input coupler and the output power at the sum frequency. Numerical simulation gives the design optimization of the system. The result of the simulation is compared with the result of a continuous-wave 355-nm generation experiment, where 0.66-W of output power was obtained. (C) 1997 Optical Society of America.