DYNAMICS OF NONLINEAR-OPTICAL PROPERTIES IN INXGA1-XAS INP QUANTUM-WELL WAVE-GUIDES/

We report the dynamics of the optical nonlinearity, measured by a weak probe propagating in single-mode InxGa1-xAs/InP quantum-well waveguid es, at wavelengths corresponding to the heavy-hole exciton resonance o r longer. The experiments are conducted at moderate pump energies (ran ging from 0.1 to a few pJ/pulse). We discovered a contribution from th e weak longitudinal component of the waveguided TM mode to the dynamic al behavior, and show that this dominates the absorption of TM-polariz ed light and the relevant optical nonlinearities at wavelengths close to the heavy-hole exciton resonance. Moreover, while at the heavy-hole exciton resonance we observe induced transmission, in the transparent region, we observe an induced-absorption behavior. We evaluate the st rong impact on the optical response of waveguides of this behavior, wh ose origin is purely excitonic, as we show in the framework of a simpl e model. We further show that the diffusion of carriers out of the wav eguiding region is negligible with respect to carrier recombination pr ocesses.