title: Directivity enhanced Raman spectroscopy using nanoantennas.
abstract: Directing the emission from optical emitters is highly desired for efficient detection and, by reciprocity, efficient excitation as well. As a scattering process, Raman benefits from directivity enhancements in both excitation and emission. Here we demonstrate directivity enhanced Raman scattering (DERS) using a nanoantenna fabricated by focused ion beam milling. The nanoantenna uses a resonant ring-reflector to shape the emitted beam and achieve DERS-this configuration is most similar to a waveguide antenna. The ring reflector boosts the measured Raman signal by a factor of 5.5 (as compared to the ground plane alone), and these findings are in quantitative agreement with comprehensive numerical simulations. The present design is nearly optimal in the sense that almost all the beam power is coupled into the numerical aperture of the microscope. Furthermore, the emission is directed out of the plane, so that this design can be used to achieve DERS using conventional Raman microscopes, which has yet to be achieved with Yagi-Uda and traveling wave antenna designs.
authors.affiliation: Department of Electrical and Computer Engineering, University of Victoria, Victoria, British Columbia V8W 3P6, Canada.
authors.forename: Aftab
authors.initials: A
authors.lastname: Ahmed
authors.forename: Reuven
authors.initials: R
authors.lastname: Gordon
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D008027:Light; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000295:instrumentation*; D010316:Particle Size; D012542:Scattering, Radiation; D013059:Spectrum Analysis, Raman / Q000295:instrumentation*