Ultraviolet lasing from single zinc oxide nanowires is demonstrated at room
temperature. Near-field optical microscopy images quantify the localizatio
n and the divergence of the laser beam. The linewidths, wavelengths, and po
wer dependence of the nanowire emission characterize the nanowire as an act
ive optical cavity. These individual nanolasers could serve as miniaturized
light sources for microanalysis, information storage, and optical computin
g.