Computational modeling of THz photoconductive antenna with plasmonic gold nanorod

Abstract

In this article, we consider a THz photoconductive antenna (THz-PCA), which consists of a THz-PCA with two electrodes, integrated with an array of plasmonic nanoislands to increase surface absorption and enhance terahertz wave generation. It is necessary to design a structure that can effectively match the phases of the external laser and the surface, which can maximize the conversion efficiency of light into THz radiation. The study is carried out with the aim of minimizing laser reflection by forming a plasmonic structure on the PCA surface and minimizing the loss of a metal electrode by forming a diffractive lens on a counter-type antenna structure. It is shown that by carefully matching the plasmon resonance wavelength of the developed plasmon structure with the wavelength of the incoming laser radiation (λ = 780 nm), almost ideal absorption can be obtained. The developed plasmon structure ensures the absorption of light and the generation of photocarriers mainly on the surface of the GaAs substrate, which is very beneficial due to the fact that surface charge carriers have a minimum distance to the antenna leads which leads to the lowest probability of recombination. The proposed structure is numerically investigated by finite element modeling based on the Maxwell wave equation for optical interaction, the drift-diffusion equation.