Doubly resonant second-harmonic generation (SHG) in a monolithic cavity is theoretically analyzed. The general expressions for the intracavity SHG are given both in transmission and in reflection. An important application concerns the case of a non-phase-matchable nonlinear material, for which a well-designed cavity can lead to cavity phase matching of the nonlinear interaction. Indeed, it is shown that both the double-resonance condition and the phase-matching condition for the two counterpropagating second-harmonic intracavity waves can be satisfied with a cavity length equal to the coherence length of the nonlinear process and with well-designed mirror phases. For that purpose, metallic mirrors are well suited, but multilayer mirrors, which act exactly as metallic mirrors as far as the second-harmonic generation process is concerned, can also be used. An optimization of those pseudometallic multilayer mirrors is performed. The possibility of maintaining the double resonance with only one tuning parameter is also theoretically analyzed. Examples are given in which a SHG cavity enhancement of a few tens of thousands may be achieved in a rather simple experimental setup.
© 1997 Optical Society of America
V. Berger, "Second-harmonic generation in monolithic cavities," J. Opt. Soc. Am. B 14, 1351-1360 (1997)