Femtosecond coherent polariton dynamics in the layered III-VI semiconductor InSe

Abstract

We report on the observation of the time-resolved free-induction decay (FID) in a layered III-VI semiconductor. The coherent propagation of the 1s-exciton polariton in InSe leads to severe distortions of the transmitted laser pulse shape and aperiodic modulation of the FID on a femtosecond time scale. This coherent polariton dynamic becomes operative even in optical thin samples. The characteristic dependence of the propagation beats as a function of sample thickness and excitation energy is demonstrated. The major features of the polariton dynamics are well described by coupled Maxwell and semiconductor-Bloch equations for linear pulse propagation. The scattering of polaritons by carriers and phonons is studied at different excitation densities and lattice temperatures.