Carbon nanotube-based electrically tunable broadband terahertz absorbers

Abstract

Terahertz (THz) absorbers are vital for confining electromagnetic waves in a wide range of light-matter applications. The actively tunable elements for improving the operation bandwidth limitations and the polarization features of absorbers are essential indexes for evaluating their performance. Therefore, THz absorbers with active functionality, polarization sensitivity, and straightforward fabrication are in high demand. Here, we present carbon nanotube (CNT)-based electrically tunable THz absorbers in an asymmetric Fabry‒Perot cavity. The self-assembled CNTs provide active electrical tunability as well as polarization selectivity. The experimental results show that absorbers composed of continuous and unstructured films exhibit almost perfect absorbance up to 99% from 0.2 THz to 1.6 THz. The absorbance of broadband absorbers is tuned from 48% to 99% at 1.6 THz, and the modulation depth (MD) is as high as 52%. The proposed electrically tunable absorbers with a straightforward fabrication method outperform most absorbers; these proposed absorbers promote THz applications such as filtering, biosensing, optical switching, polarized imaging, and telecommunication.