Photoluminescence Scanning Near-Field Optical Microscopy on III–V Quantum Dots

Abstract

We show photoluminescence images of buried quantum dots with a spatial resolution better than 250 nm. Uncoated fibre tips are used in shared aperture mode to illuminate and to detect the excited photoluminescence intensity in the optical near-field of the sample. In a recent publication [1], it was shown that observing only the reflected light using uncoated fibre tips in shared aperture mode it is impossible to exceed the Rayleigh diffraction limit. Nevertheless, by detecting the photoluminescence intensity we demonstrate here that a sub-wavelength spatial resolution of approximately λ/5 = 250 nm can be achieved. The comparison of far-field and near-field spectra leads to the mechanism of spatial resolution and intensity enhancement in this experiment. The PL intensity is dominated by the coupling of the uncoated fibre tip with the luminescent quantum dot and has an exponential decay with the sample probe distance.