Surface plasmon resonances of optical antenna atomic force microscope tips

A method for fabricating optical antennas on atomic force microscope probes using focused ion beam modification is described. We numerically demonstrate that these optical antenna probes provide a large near field intensity enhancement when illuminated at their resonant wavelengths. We experimentally measure the plasmon resonant wavelengths of probes with various lengths. Both simulation and experiment indicate that the resonant wavelength redshifts with increasing antenna length. We anticipate that the optical antenna tips could be used for mapping the field distributions of nanophotonic devices or for high spatial resolution spectroscopy.