Abstract

After the theory of Smith,¹ the nonlinear crystal is treated as a nonlinear (variable) output coupler. There is an optimum nonlinear coupling K_opt, corresponding to an optimum length, that provides the highest harmonic output power. A short nonlinear crystal is preferred because of its large phase-matching acceptance and low passive loss. Additionally, chaotic intensity fluctuations are avoided by low nonlinear coupling.² To get a high efficiency at low nonlinear coupling, the passive cavity loss has to be reduced to a minimum.

© 1995 Optical Society of America