The Planar Parabolic Optical
Antenna
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Abstract
One of the simplest and most common structures used for
directing
light in macroscale applications is the parabolic reflector. Parabolic
reflectors are ubiquitous in many technologies, from satellite dishes
to hand-held flashlights. Today, there is a growing interest in the
use of ultracompact metallic structures for manipulating light on
the wavelength scale. Significant progress has been made in scaling
radiowave antennas to the nanoscale for operation in the visible range,
but similar scaling of parabolic reflectors employing ray-optics concepts
has not yet been accomplished because of the difficulty in fabricating
nanoscale three-dimensional surfaces. Here, we demonstrate that plasmon
physics can be employed to realize a resonant elliptical cavity functioning
as an essentially planar nanometallic structure that serves as a broadband
unidirectional parabolic antenna at optical frequencies