Radiation transfer through nanoscale apertures

An H-shaped nano-aperture used as a high efficient near-field radiator is demonstrated. The transfer efficiency higher than unity and nanoscale radiation spot can be achieved simultaneously in the near field compared with regular apertures. The radiation enhancement is ascribed to the fundamental electric-magnetic field propagating in the TE10 mode concentrated in the gap between the ridges, which provides the electric dipole-liked behavior. The optimal performance of nano-apertures could be fulfilled by proper design of the geometry of the aperture, choosing good conducting metals as the film materials and low refractive substrate. As a demonstration, a super small spot about 20 nm×18 nm is achieved through the radiation of a nano-aperture with a narrow gap of 12 nm×8 nm.