Spatially and temporally resolved near-field spectroscopy of single GaAs quantum wires

Single GaAs quantum wires grown on patterned (311)A GaAs substrates are studied by steady-state and time-resolved near-field optical spectroscopy with a spatial resolution of 250 nm. The photoluminescence and photoluminescence excitation spectra as well as lateral variations of the quasi-one-dimensional confinement potential of the quantum wire are determined by measurements in the temperature range from 10 to 300 K. Diffusive transport of excitons and trapping into the quantum wire are directly monitored in picosecond luminescence experiments, allowing a quantitative measurement of exciton mobility. First near-field pump-probe experiments with femtosecond time resolution demonstrate the potential of this technique for monitoring spatio-temporal dynamics on ultrafast time scales.