Antibonding plasmon mode coupling of an individual hole in a thin metallic film

The polarization dependence of the optical properties of individual subwavelength holes in a thin metallic film is studied using terahertz time-domain spectroscopy. We show that for parallel polarization of the incident light, the coupling is predominantly to short-range bonding film plasmons while for perpendicular polarization the incident light couples more efficiently to long-range antibonding film plasmons. These results represent a direct observation of antisymmetric hybridized plasmons and clarify the nature of plasmonic excitations in metallic structures with subwavelength-scale geometrical features. They show that polarization can be used as a means for selective excitation of film plasmon modes.