PHASE-SENSITIVE RESONANT ULTRAFAST REFLECTION FROM GAAS QUANTUM-WELLS

The method of frequency-resolved optical gating (FROG) was applied to study the electric field reflected from MBE grown GaAs/AlGaAs quantum well samples after excitation with femtosecond laser pulses in resonan ce with the exciton transitions. The fluence of tile incident laser pu lses was varied by more than three orders of magnitude. In the linear regime we find good agreement of the FROG signals with the results of a dielectric model that takes into account the detailed structure of t he sample. In the high intensity regime a strong enhancement of the re flected field due to the quantum well exciton transitions is observed.