MAGNETOSTATIC MODULATION OF NONLINEAR REFRACTIVE-INDEX AND ABSORPTIONIN QUANTUM WIRES

The magnetic-field dependence of the nonlinear differential refractive index Delta n and absorption Delta alpha in quantum wires-measured by non-degenerate pump and probe spectroscopy-is investigated theoretica lly. The nonlinearities arise from population saturation of the excito nic state under optical pumping and the formation of biexcitons (excit onic molecules). Both Delta n and Delta alpha exhibit positive and neg ative peaks at certain pump and probe detuning frequencies associated with the formation of biexcitons and bleaching of excitons, respective ly. The amplitude, lineshape and the frequency at which these peaks oc cur can be modulated by a magnetic field which opens up the possibilit y of realizing novel magneto-optical devices. Additionally, the magnet ic field may allow us to realize a relatively large variation in the d ifferential refractive index over a range of frequencies without signi ficant accompanying absorption, thereby allowing the observation of op tical bistability. (C) 1998 Academic Press Limited.