Nanostructures in metal films for enhanced transmission and polarization controlled diffraction

• Main Author: Marthandam, Pramodha
• Other Authors: Gordon, Reuven
• Language: English; en
• Published: 2007
• Subjects: Surface waves; diffraction; Bragg gratings; UVic Subject Index::Sciences and Engineering::Engineering::Electrical engineering
• Online Access: http://hdl.handle.net/1828/286

A novel nano-structure is proposed to enhance extraordinary optical transmission from a periodic array of nano-holes. The Plasmonic Bragg reflector works by recapturing surface plasmons that are scattered off the edge of the array during the extraordinary optical transmission process, and reflecting them back towards the array where they can interfere with the light and enhance transmission. This reduces losses from a subwavelength aperture array. The reflectors are positioned to reflect in-phase with the light transmission. Polarization sensitivity of the plasmonic Bragg reflector is demonstrated. Modulation of the transmission is achieved by varying the separation between the array and reflectors. Isolation of adjacent structures on a plasmonic device by the use of the Bragg reflectors is attempted. Transmission and diffraction properties of quasiperiodic nano-hole arrays in a gold film are studied. Resonant transmission is observed, whose values do not simply match surface plasmon wave-vector values. Rotationally symmetric diffraction from the quasicrystal nano-hole array. This diffraction is seen to be controllable by the polarization of the excitation laser. Finite difference time domain calculations of the quasiperiodic array are performed to better understand the origin of the observed transmission resonances. Good agreement between theory and experiment is observed. Calculations show the formation of near-field hot-spots over the structure.