Optical frequency conversions in nonlinear medium with periodically modulated linear and nonlinear optical parameters

A new method considering both linear and nonlinear optical parameter modulation and propagation loss is proposed to treat second-order nonlinear optical interactions in nonlinear media having periodic structures. Mathematical expressions are derived for difference frequency generation (DFG) and compared with those for second-harmonic generation (SHG). Wavelength conversions around 1.55 /spl mu/m, which are very interesting in optical communication systems, are studied for semiconductor DFG devices with periodic structures. Semiconductor (e.g., AlGaAs) DFG devices of standard device lengths (several mm) and pump light intensities (10/sup 5/ kW/cm/sup 2/) are shown capable of practical level conversion efficiencies (/spl sim/10%) and extremely wide bandwidths (/spl ges/100 nm). Effects of propagation loss in DFG devices are also examined.<>