We discuss low temperature near-field scanning optical spectroscopical
studies of single, nanometer dimension, cleaved edge overgrown quantu
m wires. We use the enhanced spatial resolution of near-field microsco
py, to spectroscopically investigate these single wires, which are ina
ccessible to conventional far-field optical spectroscopy, We thus perf
ormed a direct experimental comparison between a two-dimensional quant
um system and a single genuine one-dimensional quantum system. We show
that the photoluminescence of a single quantum wire is easily disting
uished from that of the surrounding quantum well. Emission from locali
zed centers is shown to dominate the photoluminescence from both wires
and wells at low temperatures. A factor of three enhancement in the o
ptical absorption of a wire, in comparison with that of a similar well
, is concluded from the photoluminescence excitation data.