Dephasing of Excitonic Polaritons Confined in GaAs Thin Films

Abstract

We report the dephasing of excitonic polaritons due to propagation in GaAs thin films measured using a reflectiontype pump-probe technique. The rise time of the transient signal due to the propagation of excitonic polaritons decreases with an increase in temperature. This decrease originates from the dephasing of excitonic polaritons. From the analysis based on exciton-phonon scattering, the interaction with optical phonons mainly characterizes the dephasing process of exciton polaritons. Moreover, the result of the comparison of the temperature dependence of the damping factor estimated from the rise time with that estimated from the photoluminescence width indicates that an interaction with optical phonons in the propagation process is larger than that in the momentum relaxation process.

Observation of quantum beat oscillations and ultrafast relaxation of excitons confined in GaAs thin films by controlling probe laser pulses

“…The Al 0:3 Ga 0:7 As barrier layer has sufficient thickness to confine the excitons in the GaAs thin films. 11,[19][20][21] The GaAs layer thickness is larger than the exciton Bohr radius (11 nm); therefore, the center-of-mass motion of excitons is confined. The transient response was measured at 4 K by using a reflection-type pump-probe technique.…”

“…RESULTS AND DISCUSSION Figure 1(a) shows the PL spectrum for the evaluation of exciton energies. By comparison of their peak energies with the calculation results for exciton energies based on the model of quantization of the center-of-mass motion of excitons, 20,21 we determined the origins of the PL peaks. This calculation does not include the effect of the radiative shift caused by coupling with light fields.…”

“…The signal measured in the negative time region originates from the polariton propagation. [20][21][22] The signal clearly varies with DE of the probe pulse. The signals obtained by using a probe pulse with DE > 1:2 meV show ultrafast components around zero delay, which had not been observed by a pump-probe technique in our previous studies, which employed a pump-probe technique with the broadband pulses to probe the response of the several exciton states.…”