State filling, Coulomb, and trapping effects in the optical nonlinearity of CdTe quantum dots in glass

Abstract

Microcrystallites of CdTe were grown in a special-formula glass, yielding CdTe dots; the linear-absorption spectrum exhibits as many as six quantum-confinement peaks. Excitation of the sample with pulses ranging from femtoseconds to microseconds has allowed us to distinguish between various mechanisms for optical nonlinearity. At very early times, phase-space filling and Coulomb interaction between the excited charged carriers is responsible for the absorption changes, δα. At later times, Coulomb effects due to trapped carriers remain and last for nanoseconds or microseconds.