Addressing and imaging high optical index dielectric ridges in the optical near field

Experimental observation of light coupling between TiO(2) integrated waveguides of subwavelength cross section and pure three-dimensional evanescent light fields is reported. This near-field optical phenomenon is produced by controlling the location of the focusing of a laser beam totally reflected at the surface of the sample. The phenomenon is observed in direct space with a photon scanning tunneling microscope. Dielectric ridges several tens of micrometers long have been efficiently excited with this technique. Upon excitation, the extremities of the linear dielectric wires display intense light spots localized both inside and around the ridge. For ridge lengths up to 30 microm, the observed phenomenon has been reproduced numerically with a parallel implementation based on the three-dimensional Green dyadic method.