Scattering Suppression and Absorption Enhancement in Contour Nanoantennas

Abstract: The expanding application spectrum of plasmonic nanoantennas demand versatile design approaches to tailor the antenna properties for specific requirements. The design efforts primarily concentrate on shifting the operation wavelength or enhancing the local fields by manipulating the size and shape of the nanoantenna. Here, we propose a design path to control the absorption and scattering characteristics of a dipole nanoantenna by introducing a hollow region inside the nanostructure. The resulting contour geometry can significantly suppress the scattering of the dipole nanoantenna and enhance its absorption simultaneously. Both the dipole and the contour dipole nanoantenna couple to equivalent amount of the incident radiation. The dipole nanoantenna scatters 84% of the coupled power (absorbs the remaining 16%) whereas the contour dipole structure scatters only 28% of the coupled power (absorbs the remaining 72%). This constitutes the transformation from scatter to absorber nanoantenna. The scattering of a contour nanoantenna can be further suppressed by incorporating a lossless dielectric in the hollow region without altering its absorption. We also demonstrate the applicability of scattering suppression and absorption enhancement features of the contour design in other nanoantenna geometries such as the self-assembly compatible nanoantenna structures of nanodisk and nanoring chains. The benefits of the contour design can be readily utilized in diverse applications; including bioplasmonics, medical diagnosis/therapy, cloaked sensing, photovoltaics and thermoplasmonics.