Vertical versus planar pulsed photoconductive antennas that emit in the terahertz regime

Abstract

The design process of a photoconductive antenna (PCA), which emits efficiently in the electromagnetic terahertz range, demands some considerations that are discussed through this work. In this work, several essential characteristics of a photoconductive antenna made with LT-GaAS are studied by means of well established commercial software (COMSOL 5.3 [1]). An approach to the efficiency is also made through the study of geometry, the laser illumination position, the substrate doping distribution, the direction of the bias applied to the semiconductor, the matching impedance at the laser operating frequency and, finally, the plasmonics effects or penetration laser enhancement due to the use of nano antennas. We study and compare two kinds of structures, one which is quasi-bidimensional or planar and the other which is vertical. Additionally, the photoconductive antennas are also modeled by using a simplified equivalent circuit which helps to understand the antennas' performance. Therefore, some fundamental parameters, like the transient capacitance between the metal contacts are also studied. Furthermore, we introduce an optimized vertical design which achieves the best results. (C) 2018 Elsevier GmbH. All rights reserved.