Efficient directional beaming from small apertures using surface-plasmon diffraction gratings.

We demonstrate efficient optical directional beaming using an array of sub-wavelength patterns on a metallic surface. Specifically, a sub-wavelength sized slit placed next to a periodic grating is designed and optimized to realize maximum coupling efficiency and directional radiation into a leaky-wave plasmonic mode. Collective scattering from the corrugations forming the grating is synthesized to radiate towards the desired direction, and efficient beaming is achieved through tailoring the design parameters with a simple analytical model. We also prove that directivity can be further enhanced by improving the slit-grating coupling efficiency through efficient plasmon generation, showing improved angular response in far-field radiation. [ABSTRACT FROM AUTHOR]