Plasmon-enhanced terahertz emission in gradedspacing photoconductive antennas

Abstract The generation of terahertz (THz) radiation by a photoconductive antenna (PCA) is investigated through the interaction between a laser and a semiconductor. The dynamic changes of charge carriers on the antenna surface under 50 fs laser excitation (λ=800 nm) are simulated using COMSOL Multiphysics v6.1 software based on the finite element method. The electric field radiation resulting from changes in the semiconductor surface electric current is simulated using CST Studio Suite 2022. A new PCA with unequal spacing electrodes is presented, which generates a non-uniform field using a metal microstructure (500 nm height, 500 nm diameter). Finite-difference time-domain (FDTD) simulations revealed more pronounced surface plasmon resonance enhancement effects for the new PCA, with a ~1.3-fold increase in light absorptivity and a ~130-fold increase in electric field intensity. This leads to a ~1.6-fold enhancement in THz radiation intensity. Additionally, the directivity of the new PCA increases from 1.2 dBi to 7.17 dBi at 1.3 THz. This PCA is designed for straightforward fabrication and significantly enhances THz radiation intensity, aiming to meet the demands of rapidly developing communication technologies.