| In 2001, Dr. Xiaolei Shi et al. proposed a C shaped single aperture design that under certain irradiation conditions can achieve high spatial resolution (lambda/10) with near field intensity and power throughput orders of magnitude greater than those of a square or circular aperture with the same spot size. The C shaped aperture represents an understudied category of resonant apertures that forms the bridge between the small aperture regime and the large aperture regime.; This thesis presents my study on resonant nano-metallic apertures, specifically, the physical mechanism behind the resonance transmission and field enhancement. Both the FDTD simulation method as well as a flow topology visualization tool is used. Meaningful 3D flow topology features and structures are revealed in the time-averaged power flow field near the apertures and are linked to the incident polarization, wavelength, aperture geometry, and charge/current distributions on the metal plane. The source of transmission resonance is determined to be the oscillating equivalent electric dipoles formed by induced charges on the aperture edges. Optimization of transmission and field enhancement rests on maximizing the induced equivalent dipole strength. Behaviors of various resonant apertures are explained based on this dipole formulation. Several basic aperture design rules are summarized, illustrated and explained. Two new apertures designs based on the original C aperture are presented. A spot size (1/15) x (1/18) lambdares2 , a throughput of 10.2 and a field intensity hundreds of times the incident intensity are achieved with the same minimum feature size as the original C aperture. Additional transmission resonances associated with the thickness are found, and their physical mechanisms are determined. Based on the understanding of the physical processes involved in aperture surface resonance and thickness resonance and their mutual coupling, a gold C aperture waveguide design is presented that shows excellent field confinement (-lambda/10) and a projected decay constant of 1.74dB/micron with a total throughput of 3.14 for a 1.1-micron guide operated at 1.5-micron wavelength. A systematic study of 2D metal slits in the "resonance slit regime" is also carried out in both thin film cases and thick film cases. |
