Nonlinear effects in coplanar GaAs/InGaAs strained-layer superlattice directional couplers

Abstract

We report on the performance characteristics of InGaAs/GaAs strained-layer superlattice coplanar ridge-type directional couplers realized by molecular beam epitaxy. The measured power transfer characteristics with 1.15 μm incident photoexcitation demonstrate nonlinear coupling due to absorption associated with the tails of the excitonic resonances in the quantum wells. From a theoretical fit of the measured data, the nonlinear refractive index coefficient, n2, of the multiquantum well is found to be 2.25×10−7 cm2/W. This agrees very well with a value of n2=1.9×10−7 cm2/W obtained independently on the same material from interferometric measurements.