Giant Terahertz Polarization Rotation in Ultrathin Films of Aligned Carbon Nanotubes

TL;DR

This paper demonstrates giant polarization rotation of terahertz waves using ultrathin, aligned carbon nanotube films, enabling efficient polarization control in a minimal interaction length for advanced optical applications.

Contribution

It introduces a novel ultrathin, high-density aligned carbon nanotube film that achieves unprecedented polarization rotation in the terahertz range, with a detailed model explaining the anisotropic optical response.

Findings

Achieved up to 20° polarization rotation in transmission

Achieved up to 110° polarization rotation in reflection

Identified a 'magic' angle for maximum rotation

Abstract

For facile manipulation of polarization states of light for applications in communications, imaging, and information processing, an efficient mechanism is desired for rotating light polarization with a minimum interaction length. Here, we report giant polarization rotations for terahertz (THz) electromagnetic waves in ultrathin (~45 nm), high-density films of aligned carbon nanotubes. We observed polarization rotations of up to ~20{\deg} and ~110{\deg} for transmitted and reflected THz pulses, respectively. The amount of polarization rotation was a sensitive function of the angle between the incident THz polarization and the nanotube alignment direction, exhibiting a `magic' angle at which the total rotation through transmission and reflection becomes exactly 90{\deg}. Our model quantitatively explains these giant rotations as a result of extremely anisotropic optical constants, demonstrating that aligned carbon nanotubes promise ultrathin, broadband, and tunable THz polarization devices.