Ultra-Fast Radiative Decay of Spatially Extended Non-Dipole Type Excitonic State

Abstract

By means of the non-local theory of the pulse response and the analysis of the exciton–radiation coupled modes, we elucidate a recently observed short response time of degenerate four-wave mixing (DFWM) of weakly confined excitons in a thin film. Especially, it is expected that the excitons with non-dipole type of center-of-mass wavefunctions exhibit a peculiar thickness dependence owing to a spatial structure of the radiation field. The experimental results of the three-beam DFWM of GaAs thin layers strongly support our theoretical explanation of the radiative decay that is beyond the long wavelength approximation.