Ultrafast phase relaxation of excitons via exciton-exciton and exciton-electron collisions.
01 January 1986
The ultrafast relaxation of excitons in GaAs, coherently excited by a short optical pulse and subjected to collisions with free carriers and noncoherent excitons, which are independently created by a second sychronized light pulse, is studied directly in the time domain by probing the excitonic phase coherence. The dependence of the excitonic phase coherence on the exciton density reveals the exciton-exciton collision efficiency of 1.6*10(-4)cm(3)s(-1). Exciton free-carrier scattering is found to be 10 times more efficient than exciton-exciton scattering due to the long range character of the Coulomb interaction. A blue shift of the corresponding absorption line increasing with the exciton density is observed indicating the repulsive character of the short-range exciton-exciton interaction.