MODELING OF NONLINEAR ABSORPTION AND REFRACTION IN QUANTUM-WELL STRUCTURES FOR ALL-OPTICAL SWITCHING

We present a realistic model of the electromagnetic response in excited, type-I semiconductor quantum wells. A multisubband analysis of the room temperature band edge spectra is introduced, in which the plasma effects are determined through an iterative, numerical solution of a generalized Bethe-Salpeter equation. Our method allows the treatment of situations in which transitions higher than the first give sizeable contributions to the nonlinear optical properties, as in coupled quantum wells or in the propagation of TM modes within waveguides based on quantum confined structures. Further, the method accounts for the effects of finite quantum-well thickness and incorporates a phenomenological description of the width of the resonance lines. The behavior is compared and contrasted to more idealized models introduced in earlier works, where single-subband, purely 2-D systems are treated. Computer generated spectra are compared with absorption spectra experimentally obtained in moderately strained InGaAs-InP QW's.