Picosecond and femtosecond near-field optical spectroscopy of carrier dynamics in semiconductor nanostructures

Quasi-two-color femtosecond pump-probe spectroscopy and near-field scanning optical microscopy are combined to study the carrier dynamics in single se miconductor nanostructures. In temporally, spectrally and spatially resolve d measurements with a time resolution of 200 fs and a spatial resolution of 200 nm, the nonlinear change in reflectivity of a single quantum wire is m apped in real space and time. The experiments show that carrier relaxation into a single quantum wire occurs on a 100 fs time scale at room temperatur e. First experimental evidence is given for carrier transport along the wir e axis on a picoseond time and 100 nm length scale. (C) 1999 Elsevier Scien ce B.V. All rights reserved.