SNOM-induced photoluminescence of individual InGaAs quantum dots using etched metal-coated fibre tips

Scanning near-field optical microscopy is used to investigate the photoluminescence of individual In0.4Ga 0.6As quantum dots. The high transmission efficiency of etched fibre tips allows investigations of quantum dots at room temperature with sufficient intensity, even after coating the tip with metal for background elimination. The pure background-free signal of single quantum dots results in Lorentzian photoluminescence spectra with finite line widths of 10–20 meV at room temperature to <1 meV at 4 K. This is in contrast to the expectation of extremely narrow lines in the microelectron-volt region.