Collective Antenna Effects in the Terahertz and Infrared Response of Highly Aligned Carbon Nanotube Arrays

TL;DR

This study investigates the terahertz and infrared electromagnetic response of highly aligned single-wall carbon nanotube arrays, revealing their antenna-like behavior and polarization-dependent transmission characteristics.

Contribution

It provides a detailed analysis of the collective antenna effects in aligned nanotube arrays, combining experimental spectroscopy with electromagnetic modeling.

Findings

Extreme polarization anisotropy below 3 THz

Peak attenuation around 10 THz in the parallel polarization

Sample acts as an effective antenna with dominant scattering

Abstract

We study macroscopically-aligned single-wall carbon nanotube arrays with uniform lengths via polarization-dependent terahertz and infrared transmission spectroscopy. Polarization anisotropy is extreme at frequencies less than $\sim$3 THz with no sign of attenuation when the polarization is perpendicular to the alignment direction. The attenuation for both parallel and perpendicular polarizations increases with increasing frequency, exhibiting a pronounced and broad peak around 10 THz in the parallel case. We model the electromagnetic response of the sample by taking into account both radiative scattering and absorption losses. We show that our sample acts as an effective antenna due to the high degree of alignment, exhibiting much larger radiative scattering than absorption in the mid/far-infrared range. Our calculated attenuation spectrum clearly shows a non-Drude peak at $\sim$10 THz in agreement with the experiment.