Abstract

The large optical nonlinearities exhibited by III-V multiple quantum well (MQW) materials¹ have afforded some optimism in achieving large all-optical switching ratios with low threshold power and short device length. By using multiple quantum wells in the coupling as well as the guiding regions, Kam Wa et al. was the first to demonstrate partial switching between two parallel GaAs/AlGaAs MQW channel waveguides.² This device, however, exhibited very high loss. Cada et al. argued that much better performance in terms of lower loss may be achieved by placing the MQW nonlinear medium in the coupling region only,³ but the experimental device still exhibited only partial switching.⁴ Several approaches to solve the problem of the nonlinear directional couplers in semiconductors have been proposed and since no general exact analytical treatment including absorption and nonlinear saturation is available, approximations or numerical simulation must be used. In this regard, Caglioti et al.⁵ presented a more complete analytical estimate for the characteristics of nonlinear directional couplers for operation above the resonance with large detuning.

© 1991 Optical Society of America