Professor Robert Taylor

Abstract:

We present a combined experimental and theoretical investigation of intra- and intersubband carrier relaxation in GaAs/AlAs quantum wells following femtosecond laser excitation at low density. Time-resolved optical absorption has been measured using 125 fs pulses from a tunable Ti:sapphire laser which allows carriers to be excited preferentially into different subbands. The experiments have been analyzed using a multi-subband Monte Carlo simulation which contains all the important scattering mechanisms. Electron-phonon scattering rates obtained from dielectric continuum theory have been used, and we find excellent agreement with the experiment. The dominance of interface phonons in intrasubband relaxation is confirmed. © 1995 American Institute of Physics.

Abstract:

We report time-resolved optical transmission and photoluminescence measurements of exciton dynamics and recombination in a ZnSe/ZnSe 0.82S0.18 superlattice which displays low-threshold lasing. The carrier densities in our experiments are below threshold for stimulated emission. We find clear evidence for strong exciton-LO phonon scattering which gives rise to emission at the same wavelength where stimulated emission is reported to occur.

Abstract:

We report time-resolved luminescence measurements of MBE-grown ZnTe/GaSb. Above-bandgap excitation is provided by second-harmonic generation using infrared pulses from a Ti:sapphire laser. Cooling of the hot-carrier distribution is observed on a picosecond time-scale, and is seen to be limited by phonon bottle-necking at these carrier densities, allowing an estimate of the LO phonon lifetime in this material.