Dynamics of the transition from weak to strong exciton‐photon coupling regime in a GaAs microcavity: angle resolved measurements

Abstract

AbstractThe emission dynamics of a GaAs microcavity with embedded quantum wells at different angles of observation with respect to the sample normal under conditions of nonresonant picosecond‐pulse excitation is studied. At considerably high excitation densities, above a certain threshold, a very intense, fast, and spectrally narrow (at small angles of observation) component in the PL dynamics appears at short times, with the spectral position corresponding to the bare cavity mode, indicating the onset of lasing in the weak coupling regime. At longer times lasing ceases and the transition from weak to strong coupling regime is observed, as it follows from the spectral positions of the peaks in time‐resolved spectra at different angles of observation.At moderate excitation densities, kinetic dependences of the spectral shift and width of the lower polariton emission line (these parameters are often used to distinguish between strong and weak coupling regimes) as a function of angle of observation (polariton energy) are analyzed. In particular, it is shown that the decay time of the spectral shift is almost independent of the polariton energy and could be used as the characteristic time of the transition from weak to strong coupling regime. On the other hand, the decay time of the emission line broadening strongly depends on the polariton energy, indicating that the linewidth kinetics is essentially determined by the cooling of the electron‐hole system. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)