Time-resolved nonlinear spectroscopy of excitons

J. M. Hvam

Duncan G. Steel, Steven T. Cundiff, H. Wang

Satoshi Ideshita, Yasuaki Masumoto

We present the detailed experimental results of the time-resolved nonlinear luminescence of excitons in undoped GaAs-AlAs quantum wells. The observed nonlinearity results from the saturation in luminescence originated from the phase space filling and exchange effects of carriers. In some temporal profiles of nonlinear luminescence, anomalous anti-correlation profile has been observed. The origin of anti-correlation is ascribed to be the finite rise time of the exciton population at the luminescent tail state in the exciton band.

Duncan G. Steel

Work has concentrated on the development of high resolution frequency domain nonlinear spectroscopy methods as well as the use of picosecond coherent techniques such as. the stimulated photon echo and time resolved free polarization decay. Using these methods, new understanding has been obtained on the dynamics associated with excitons in GaAs/AlGaAs quantum well structures, particularly as these dynamics are affected by disorder.

Ida Maria Catalano, Aldo Cingolani, Michele Ferrara +2 more

Han Q. Le, J.V. Hryniewicz, W. D. Goodhue +1 more

Optical nonlinearities of Al(x)Ga(1-x)As/GaAs asymmetric coupled quantum wells within a p-i-n structure have been observed by using time-resolved spectroscopy. Under photoexcitation, exciton absorption lines exhibit spectral shifts of as much as approximately 1 meV. The recovery times of these spectral shifts are of the order of hundreds of picoseconds when the excitation photon is above the lowest exciton state but become less than 10 psec when excitation is below the lowest exciton state, indicating a virtual process. The behavior of these spectral shifts is consistent with the presence of a polarization induced by optical pumping. The polarization is believed to be due to the excitons that have nonvanishing electric dipole moments along the axis of the asymmetric coupled quantum wells.