Optical absorption enhancement in LTG-GaAs for efficiency improvement of THz photoconductive antennas

Abstract

A novel structure for THz photoconductive antennas (PCA) has been proposed to enhance the optical absorption, and consequently the power conversion efficiency. In the proposed structure, the surface of the low-temperature-grown GaAs (LTG-GaAs) substrate is textured to create an array of nanodisks where an array of silver nanodisks is placed 300 nm under the surface. The simulation results indicate that laser pulse reflection from the LTG-GaAs surface decreases to less than one percent as compared to around 30 % reflection for surfaces with no nanostructure features. As a result, the photo current increases by a factor of around 2.6 for the proposed structure. This would increase the generated THz power by the current enhancement factor squared.