Interaction of Multiwalled Carbon Nanotube Aerogels with Quasi‐Optical Terahertz Beams

Abstract

This article presents the measurements of the reflectance from a plane‐parallel aerogel sample formed by multiwalled carbon nanotubes (MWCNTs) in the terahertz range. With an increase in frequency from 100 GHz to 1.5 THz, the reflectance decreases by more than a factor of two. Based on the experimental data and the well‐known wire medium model formed by a three‐dimensional lattice of intersecting conductors, a model of a regular wire medium is constructed using MWCNTs with effective electrophysical characteristics equivalent to those of an irregular aerogel medium. This model reveals that a significant drop in the reflectance in the terahertz frequency range occurs because the plasma frequency of the equivalent medium is located here. The model allows estimating the properties of the aerogel environment in the frequency range extending up to 5 THz and with variations in the packing density of MWCNTs in aerogel. Estimates of the reflection, transmission, and absorption are presented for the case of normal incidence on a thin (submillimeter) layer of such a medium. The aerogel absorption at a given conductivity of CNTs is determined by their packing density.