Exciton radiative lifetime of quantum rods in reflectivity

Time-resolved differential reflectivity (TRDR) experiments were performed on columnar InAs/GaAs quantum rods (QRs). A resonant-like enhancement of the exciton radiative lifetime near the centre of the inhomogeneously broadened QR-size distribution is observed. At low pump excitation density, the TRDR decay time shows the expected excitonic behaviour. At increased pump excitation, a quasi-resonant radiative lifetime develops, which seems to be dependent on the excited QR density being resonant with the probe laser spectrum. The resonance is interpreted as due to electromagnetic coupling between randomly distributed excited QRs that are resonant with the probe laser.