Crucial effects of coupling coefficients on quasi-phase-matched harmonic generation in an optical superlattice

Coupling of optical parametric processes in an optical superlattice through quadratic nonlinearity was analyzed theoretically. Solving the coupled equ ations, we found that efficient quasi-phase-matched third-harmonic (TH) gen eration depends not only on the magnitude of the coupling coefficients but also on their ratio Theoretically, all the fundamental energy can be transf erred to the TH at a particular ratio. In other cases, there exists an opti mum condition that corresponds to a maximum TH conversion efficiency. The r esult is of practical importance for the design of TH devices. (C) 2000 Opt ical Society of America OCIS codes: 190.4410, 190.2620, 130.4310.