ENHANCEMENT OF THE 3RD-ORDER NONLINEAR-OPTICAL SUSCEPTIBILITY IN SI QUANTUM WIRES

Recent observation of efficient light emission from porous silicon has attracted much attention and renewed interests in the study of nonlin ear optical properties of nanometer-sized quantum systems. In this pap er, we study the third-order nonlinear optical susceptibility of semic onductor quantum wires. The quantum wires are taken to be circular col umns with a cross section size of approximately 1 nm. The excitonic ef fects are taken to be the major electronic excitations. We find that t he quantum confinement of the excitons greatly enhances the third-orde r optical nonlinear susceptibility in a quantum wire. The source of th e enhancement is primarily the confinement-induced localization of exc itons. The large enhancement of the third-order optical nonlinearity e stimated here is consistent with the recent observation of the efficie nt infrared-up-conversion luminescence in porous silicon.