Controlled Exciton-Plasmon Coupling in a Mixture of Ultrathin Periodically Aligned Single-Wall Carbon Nanotube Arrays

TL;DR

This paper theoretically investigates exciton-plasmon interactions in ultrathin, periodically aligned carbon nanotube films, revealing negative refraction behavior and tunable optical properties for potential metamaterial applications.

Contribution

It introduces a theoretical model of exciton-plasmon coupling in aligned CN arrays, demonstrating hyperbolic metamaterial behavior and tunable optical absorption in mixed CN films.

Findings

Negative refraction band identified in CN films.

Tunable optical absorption near exciton resonance.

Hyperbolic metamaterial behavior demonstrated.

Abstract

We study theoretically the in-plane electromagnetic response and the exciton-plasmon interactions for an experimentally feasible carbon nanotube (CN) film systems composed of parallel aligned periodic semiconducting CN arrays embedded in an ultrathin finite-thickness dielectric. For homogeneous single-CN films, the intertube coupling and thermal broadening bring the exciton and interband plasmon resonances closer together. They can even overlap due to the inhomogeneous broadening for films composed of array mixtures with a slight CN diameter distribution. In such systems the real part of the response function is negative for a broad range of energies (negative refraction band), and the CN film behaves as a hyperbolic metamaterial. We also show that for a properly fabricated two-component CN film, by varying the relative weights of the two constituent CN array components one can tune the optical absorption profile to make the film transmit or absorb light in the neighborhood of an exciton absorption resonance on-demand.