Coherent light scattering and resonant energy transfer in an apertureless scanning near-field optical microscope - art. no. 045420

We investigate the interaction of two molecules or nanosized particles with a nearly resonant laser field under the tip of an apertureless near-held m icroscope. We show that interference of several scattering channels provide s means for enhanced spatial resolution. The visibility of two separate nan o objects is considered, and a natural definition emerges for the resolutio n of the apertureless microscope operating under conditions of nearly reson ant illumination. The probe tip creates an additional coupling channel betw een the two molecules, and thus affects the energy transfer between them. W e demonstrate that the tip can either enhance or suppress this transfer. Tw o models fur the tip geometry are considered: a simplified pointlike dipole , and a more realistic elongated spheroid. Quantitative results are obtaine d for the dependence on irradiation frequency and tip position for dielectr ic as well as metallic tips. In particular, specific results are obtained f or a silver tip under conditions of plasmon resonance, and we show that und er fully resonant conditions the tip may enhance the intermolecular energy transfer by nearly two orders of magnitude.