Obtaining super resolution light spot using surface plasmon assisted sharp ridge nanoaperture

Finite difference time domain computations is used to study surface plasmon (SP) excitation around C- and H-shaped ridge nanoapertures made in silver film. The SP enhances optical transmission, in addition to the transmission mechanism of the waveguide propagation mode and Fabry-Perot-like resonance. However, the near-field collimation of ridge aperture is found completely destroyed. On the other hand, using a bowtie-shaped aperture with sharp ridges made in silver, the loss of near-field collimation can be recovered. A super resolution optical spot with full width half magnitude as small as 12 nmx16 nm is achieved due to the resonant SP excitation localized at the tips of bowtie. Much higher field enhancement is also obtained compared to the bowtie aperture made in chromium. (C) 2005 American Institute of Physics.