Optimal design for the quasi-phase-matching three-wave mixing

Expressions for the quasi-phase-matching (QPM) three-wave mixing (TWM) with arbitrary grating structure and phase shift are obtained in this paper, fo r the first time, under the small-signal approximation. The expressions can be extensively applied to the all-optical signal processing for TWM, in wh ich the signal and pump bandwidth of the wavelength conversion in DFM and t he all-optical gate (AOG) bandwidth in SFM are all optimized. The optimal r esults from our expressions are compared with the results from the coupled- mode equations of QPM-TWM. Compared with loss free, the propagation loss in waveguides can decrease the conversion efficiency, but only a little chang e for the bandwidth. (C) 2001 Optical Society of America.