Dielectric Wavelength-Scaled Metalenses Based on an Anomalous Apodization Effect for Photoconductive Optical-to-Terahertz Switches

Abstract

A new strategy to improve the enhancement of an optical wave confinement in photoconductive antenna by implementation of a single or array of dielectric wavelength-scaled structures of different shape featuring symmetrical and broken symmetry into PCA's gap is offered. The results of the simulation and optimization of these novel-designed PCAs are discussed. The spectral and power characteristics, and the efficiency of optical-to-terahertz switches are the key parameters. To increase the efficiency of the OT conversion, the use of mesoscale dielectric particle placed onto the gap between the electrodes of optical-to-terahertz switches was offered. It has been shown, that it is possible to increase the field intensity localization of light (about 9.6 times) and to achieve the minimal beam waist of about 0.32 $\lambda_{0}$ in photoconductor, which is below the Abbe diffraction limit. The proposed design of a metalens based on a single or array of dielectric wavelength-scaled particles (dielectric grating or colloidal particles) with anomalous apodization effect can become a promising way for increasing the efficiency of an optical-to-terahertz switches and increase the photocurrent about 1.4 - 1.5 times.