A full vector analysis of near-field luminescence probing of a single quantum dot

We solve numerically the three-dimensional vector form of Maxwell’s equation for the situation of near-field excitation and collection of luminescence from a single quantum dot using a scanning near-field optical fiber probe with sub-wavelength resolution. Applying a finite-difference time-domain method, we calculate the complete vector fields emerging from a realistic probe structure, as well as the near-field luminescence image of the dot captured by the same probe. We show that a collimating effect in the high index semiconductor significantly improves the spatial resolution in excitation/collection mode. We find that the spatial resolution, image shape, and collection efficiency of near-field luminescence strongly depend on the orientation of the radiating dipole in the dot.