Investigation of terahertz photoconductive antenna based on optimized plasmonic nanostructures

Abstract

Herein, we numerically investigate terahertz photoconductive antennas (PCAs) based on optimized plasmonic nanostructures and absorption enhancement in nanocylinders. Metallic nanostructures playing an important role in nanophotonic applications are a hot topic nowadays. Such applications are possible due to their capability to focus or intensify electromagnetic fields close to the metal by employing excitation approach of surface plasmon polaritons. Plasmonic behavior in the visible to near-infrared light spectrum is achievable due to the metallic nanostructures employment. Herein, we study the absorption enhancement of silver and transparent-conducting oxides (TCO) nanocylinders with different diameters by means of effective medium approximation. This study also reports on the stronger enhancement in the case of TCO nanocylinders. The results show that resonant absorption amplitude and wavelength are dramatically affected by the thickness of the nanostructure as well as by the distances between nanocylinders. The outputs reported here provide a fertile ground for precise control of the nanowire structures for sensing and other enhanced optical applications. Because of compact structure, simple fabrication and room temperature operation, PCAs provide THz wave generation and detection. Moreover, PCAs are widely used in time domain THz imaging and spectroscopy systems for generating pulsed THz radiation. It is worthwhile noting, that in case of TCO nanocylinders, absorption enhancement for NIR wavelengths, being relevant for present THz generation setup, reaches up to 5-fold leading to 25-fold increase in THz radiation.