Optical light confinement in terahertz antennas

Abstract

We report on two approaches aimed at increasing the performance of a photoconductive antenna (PCA) due to enhanced optical light confinement in a PCA's gap. The first refers to the use of a high-aspect ratio metal grating maintaining plasmonic guided modes while the second implies an asymmetric dielectric particle combined with a prism on a metal surface to provide a sub-wavelength focusing of a laser beam. We reached a 3000-fold increase in the emitted THz power and a 25-fold THz photocurrent enhancement in a plasmon-assisted PCA; the further increase in both parameters might be reached by optimizing the geometry of the grating. We propose a new curved beam - the photonic hook plasmon that can be realized using the in-plane focusing of the surface plasmon-polariton wave through a dielectric particle. We demonstrate a potential possibility to reach predominantly a sub-wavelength focused and high-intensive beam obtained from the opposite side of the dielectric particle.