The tuning of light-matter coupling and dichroism in graphene for enhanced absorption: Implications for graphene-based optical absorption devices

TL;DR

This paper investigates how to enhance and tune optical absorption and circular dichroism in graphene by adjusting Fermi level, incident light angle, dielectric environment, and strain, with implications for optical device applications.

Contribution

It provides a comprehensive analysis of tunable parameters affecting graphene's optical absorption and dichroism, including impurity effects and strain-induced anisotropy.

Findings

Absorption can be significantly increased by tuning Fermi level and incident angle.

Impurities cause Lorentzian broadening affecting spectral features.

Strain induces circular dichroism, with differences between armchair and zigzag configurations.

Abstract

The inter-band optical absorption in graphene characterized by its fine-structure constant has a universal value of 2.3\% independent of the material parameters. However, for several graphene-based photonic applications, enhanced optical absorption in graphene is highly desired. In this work, we quantify the tunability of optical absorption in graphene via the Fermi level in graphene, angle of incidence of the incident polarized light, and the dielectric constant of the surrounding dielectric media in which graphene is embedded. The influence of impurities adsorbed on the surface of graphene on the Lorentzian broadening of the spectral function of the density of states is analytically evaluated within the equilibrium Green's function formalism. Finally, we compute the differential absorption of right and left circularly-polarized light in graphene that is uniaxially and optically strained. The preferential absorption or circular dichroism is investigated for armchair and zigzag strain.