DIRECT OBSERVATION OF SURFACE POLARITON LOCALIZATION CAUSED BY SURFACE-ROUGHNESS

Using a photon scanning tunneling microscope (operating at the wavelen gth of 633 nm) with shear force feedback we probe directly an optical field of surface plasmon polariton (SPP) while imaging simultaneously surface topography. We observe that near-field optical images, which a re generated due to the SPP excited at a rough gold film surface, exhi bit spatially localized (within 150-250 nm) intensity enhancement by u p to 7 times, We find that the positions of these bright light spots d o not correlate with the local surface topography and depend on the an gle of exciting beam incidence. We relate the observed phenomenon to t he strong localization of SPPs caused by surface roughness.