Self-consistent study of dynamical and polarization effects in near-field optical microscopy

International audienceA whole self-consistent method is developed in order to analyze the influence of incident light beam polarization on an image shape recently recorded from scanning tunneling optical devices. The electromagnetic coupling between the object and a nanometer-size detector is described from a dynamic matrix, including all dipolar correlations inside the system. This matrix, expressed in terms of field propagators, permits us to analyze the physical mechanisms responsible for the conversion of evanescent waves into homogeneous propagating modes inside the detector. The numerical results are compared with those obtained for layered metallic or dielectric nanoparticles deposited upon a glass substrate. The shape and the contrast of the images are both sensitive to the field polarization and to the external frequency in the case of metallic objects. Moreover, as was observed in experimental studies, the p-polarized mode seems to give better contrast in the images