Time-resolved phase spectroscopy from femtosecond free-induction decay

Abstract.

We report a novel two-channel experimental scheme to record femtosecond amplitude and phase dynamics for dephasing studies. The measurement of free-induction decay in one channel and pulse autocorrelation for the central wavelength of the exciting pulses at the other channel as the reference allows the recording of time-resolved amplitude and phase dynamics of the free-induction decay throughout the dephasing process. The technique is applied to the study of coherent dynamics of the photocarriers in semiconductor GaAs. The observed phase dynamics is well simulated with optical Bloch vector components analysis for the homogeneously broadened two-level model and the experimental and theoretical study is extended for the three-level system. The two-pulse-induced phase spectroscopy should be generally applicable to different kinds of materials by recording the population difference for the two-level system with pulse-induced fluorescence.