Theoretical investigations of efficient cascaded third-harmonic generation in quasi-phase-matched and -mismatched configurations

Abstract

Theoretical and numerical solutions of the nonlinear coupling-wave equations of second-harmonic (SH) and third-harmonic (TH) converters are investigated for both phase-matched and phase-mismatched configurations. For phase-mismatched TH generation, several kinds of schemes [the phase mismatch in either SH generation or sum-frequency generation (SFG) as well as the phase mismatch in both SH generation and SFG] are considered and analyzed. The optimal TH converting properties for generalized phase-mismatching operation are discussed and studied. It is found that efficient TH generation depends not only on the magnitude of the coupling coefficients but also on their ratio. A 100% TH output can be obtained at a particular ratio. The physical nature of the different ratios of the coupling coefficients is discussed.