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

We present a realistic model of the electromagnetic response in excite d, 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 g eneralized Bethe-Salpeter equation. Our method allows the treatment of situations in which transitions higher than the first give sizeable c ontributions to the nonlinear optical properties, as in coupled quantu m wells or in the propagation of TM modes within waveguides based on q uantum confined structures. Further, the method accounts for the effec ts of finite quantum-well thickness and incorporates a phenomenologica l description of the width of the resonance lines. The behavior is com pared and contrasted to more idealized models introduced in earlier wo rks, where single-subband, purely 2-D systems are treated. Computer ge nerated spectra are compared with absorption spectra experimentally ob tained in moderately strained InGaAs-InP QW's.