title: Light focusing at metallic annular slit structure coated with dielectric layers.
abstract: We report the focusing of a normally incident plane wave of 405 nm through a Ag/dielectric annular ring structure, using finite-difference time domain analysis. We first study the dependency of the focusing efficiency on slit width when the incident wave is transmitted through a single ring whose slit is filled with a dielectric. Then, light focusing by the multiple-ring structure is investigated as a function of the dielectric thickness. It is observed that the focusing is tunable between near-field and quasi-far-field regimes in the Ag/dielectric layered annular ring structure. Also, the focal intensities are remarkably enhanced by the addition of the dielectric layer, showing a Fabry-Perot-like resonance with respect to the thickness of the dielectric layer. The controllable near-field and far-field focusing offers more flexibility for applications of future nano-optic devices.
authors.affiliation: Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas 77843, USA. kohd94@gmail.com
authors.forename: Hyungduk
authors.initials: H
authors.lastname: Ko
authors.forename: Hyun Chul
authors.initials: HC
authors.lastname: Kim
authors.forename: Mosong
authors.initials: M
authors.lastname: Cheng
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006046:Gold / Q000737:chemistry*; D007368:Interferometry / Q000295:instrumentation*; D007909:Lenses; D008027:Light; D008962:Models, Theoretical; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation; D020349:Surface Plasmon Resonance / Q000295:instrumentation*
chemical_list: D006046:Gold