Third-order nonlinear susceptibility of large semiconductor microcrystallites

Abstract

We show that the theory of the third-order nonlinear susceptibility of semiconductor microcrystallites with a radius much greater than the exciton radius (‘‘weak confinement’’) has big intrinsic uncertainties due to the unknown volume dependence of the phenomenological relaxation times. These dependencies are actually sources of another type of optical nonlinearity. The third-order susceptibility increases strongly with the increasing radius of the microcrystallite in the range between 10 and 100 exciton Bohr radii and approaches a well-defined infinite radius limit.