A New Method to Treat Second-order Nonlinear Optical Interactions in Nonlinear Medium With Periodical Structure

Difference frequency generation (DFG) and second harmonic generation (SHG) in nonlinear medium with a periodical structure have attracted much attention, because of their potential applications in optical communication systems [1] and optical information processes [2]. Since all the three wavelengths involved in DFG can be in transparence region of semiconductors, semiconductor DFG devices such as AlGaAs, usually have large nonlinearity and small band-gap, are peculiar interesting. In the periodical structure, linear and nonlinear optical parameter modulations as well as propagation loss are usually very important to conversion efficiency. Although theoretical analyses that involve linear and nonlinear optical parameter modulations have been carried out extensively for SHG[3]~[6], little work has been reported for DFG [7].