title: Vertical optical antennas integrated with spiral ring gratings for large local electric field enhancement and directional radiation.
abstract: We propose a device for reproducible achievement of enormous enhancement of local electric field intensities. In each device, a metallic spiral ring grating is employed for efficient excitation of local surface plasmon resonance in the tiny gap of a vertically oriented optical antenna. Radiation from the optical antenna is collimated by the ring grating which facilitates efficient collection. As a numerical example, for a gold nanosphere placed one nanometer above the center of a gold spiral ring grating, our simulations predict an increase in local electric field intensity of up to seven orders of magnitude compared to planewave illumination, and collection efficiencies of up to 68% by an objective with a numerical aperture of 0.7. Single molecule SERS application is discussed.
authors.affiliation: National Key Laboratory of Nano/Micro Fabrication Technology, University of Michigan – Shanghai Jiao Tong University Joint Institute, Shanghai 200240, China.
authors.forename: Baoan
authors.initials: B
authors.lastname: Liu
authors.forename: Dongxing
authors.initials: D
authors.lastname: Wang
authors.forename: Chuan
authors.initials: C
authors.lastname: Shi
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Crozier
authors.forename: Tian
authors.initials: T
authors.lastname: Yang