THEORETICAL-STUDIES OF THE EFFECTS OF A MAGNETIC-FIELD ON EXCITONIC NONLINEAR-OPTICAL PROPERTIES OF QUANTUM WIRES

The magnetic-field dependence of the third-order excitonic nonlinear s usceptibility chi((3)) in a quantum wire is explored within the rotati ng wave approximation. Both the real and imaginary parts of chi((3)), arising from population saturation of the excitonic state under optica l pumping, are calculated for a GaAs wire as a function of magnetic fi eld and pump-probe detuning frequencies. The imaginary part of chi((3) ) exhibits a negative peak associated with the bleaching of the excito nic resonance and a positive, broad, off-resonance absorption peak ass ociated with biexciton formation. The amplitude, line shape, and spect ral frequency of both these peaks can be modulated by a magnetic field which indicates the possibility of using such a field to probe the me chanism underlying optical nonlinearity in a quantum wire. Furthermore , the field can also be used to tune the optical nonlinearity over a r ange of frequencies which has device applications.