title: Polarization effects in near-field excitation-collection probe optical microscopy of a single quantum dot.
abstract: 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 fibre probe with subwavelength resolution. We highlight the importance of polarization-dependent effects in both the near-field excitation and collection processes. Applying a finite-difference time domain method, we calculate the complete vector fields emerging from a realistic probe structure which is in close proximity to a semiconductor surface. We model the photoluminescence from the quantum dot in terms of electric dipoles of different polarization directions, and determine the near-field luminescence images 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 the excitation-collection mode. We find that the spatial resolution, image shape and collection efficiency of near-field luminescence imaging strongly depend on the polarization direction as represented by the orientation of the radiating electric dipoles inside the quantum dot.
authors.affiliation: NTT Basic Research Laboratories, Kanagawa, Japan. chavez@wave.brl.ntt.co.jp
authors.forename: A
authors.initials: A
authors.lastname: Chavez-Pirson
authors.forename: S T
authors.initials: ST
authors.lastname: Chu