Investigation of a turnstile nanoantenna

Dipole and bowtie are two downscale versions of electromagnetic antenna studies in the optical frequencies by using plasmonic resonances. The bowtie antennas produce a lower near-field enhancement in their feedgaps compared to the single-mode dipole antenna and besides they exhibit several resonances. However, in both the antennas, field intensity enhancement is sensitive to polarisation of incident field. In this study, the authors report the implementation of a cross nanoantenna (CNA) consisting of two orthogonal dipole nanoantennas (DNAs) with a common feedgap, investigate its directional and polarisation properties, and compare them with those of the DNA. The response of CNA is found to be independent of polarisation. Besides, the authors demonstrate that the CNA could be operated in turnstile mode, which draws useful analogies between classical electromagnetics and nanophotonics. To their knowledge this is the first proposal of a turnstile antenna in optical frequency. They believe, the polarisation-independent omnidirectional behaviour of CNA could open up new possibilities for studying the novel phenomenon of light-matter interaction.