A group of scientists at Kanagawa Academy of Science and Technology, the University of Tsukuba and the Institute of Physical and Chemical Research (Riken), all in Japan, have demonstrated a spatial resolution of 30 nm in the photoluminescence imaging of InAs quantum dots at 9 K. The team, which describes the work in the Sept. 16 issue of Applied Physics Letters, produced sensitivity-enhanced, double-tapered fiber probes for the near-field scanning optical microscope setup employed in the experiments.The researchers exposed segments of optical fiber to hydrofluoric acid and sputtered the tapered fiber with a gold film. Pounding the tip of the probe against the sample created 30- to 135-nm-diameter apertures. The technique also promises to enable the imaging and control of exciton wave functions in quantum-confined systems.