PROPAGATION OF FEMTOSECOND PULSES IN THIN ZNSE LAYERS

The transmission of optical femtosecond pulses through ZnSe/ZnSxSe1-x heterostructures is investigated in both the spectral and the temporal domain. Quantization of the polariton wave vector within the thin ZnS e layers (23 to 100 nm) leads to a variety of allowed propagating mode s which are clearly resolved in transmission spectra. Interference of all contributing modes gives rise to a very pronounced and complex tem poral beating behavior of the transmitted pulses measured with femtose cond resolution. The transmission spectra as well as the transients ta ken from different samples are consistently described by a model based on three-oscillator polariton theory using Pekar's additional boundar y conditions.