Ultrafast Recovery of Transient Changes in the Excitonic Optical Properties of InGaAs/InP Quantum Wells

Abstract

InGaAs/InP heterostructures posses strong technological relevance, particularly in view of integration of waveguide devices for interconnections and telecommunication applications. This contribution concerns the optical properties of quantum-well (QW) structures in the 1.5 μm range and the modification of these properties that can be induced by photogeneration of excitons. Beside some work already done, knowledge of those properties is far from being complete; particularly, the relative strength of optical nonlinearities induced by excitons or carriers is not properly understood. To clarify this subject we address the dynamical and spectral aspects of nonlinear behavior upon ultra-fast excitation of InGaAs/InP QWs, devoting special attention to the role of the so-called collisional broadening of the exciton peak. Experiments are done both at the exciton resonance lowest in energy and at below-resonant energies, that is in the region of strongest relevance to waveguide devices.