Faraday effect optical sensing of single-molecules by graphene-based layered structures

TL;DR

This paper proposes a graphene-based layered structure sensor that uses Faraday rotation to detect low-concentration molecules on graphene's surface, leveraging bandgap modulation effects for contact-free sensing.

Contribution

It introduces a novel optical, contact-free method for sensing molecules via Faraday rotation in a photonic graphene structure with microcavity defect channels.

Findings

Faraday rotation angles can indicate surface doping levels.

The sensor can detect low-concentration molecules without direct contact.

Reversal of Faraday rotation signs correlates with doping variations.

Abstract

Recently, modulation of the energy bandgap of graphene when gas molecules are adsorbed to its surface has been proved to be possible. Motivated by this, based on numerical calculations, we investigate the effect of the associated bandgap opening in graphene's spectrum on the sensing properties of the Faraday rotation (FR) of linearly polarized electromagnetic modes in a 1D photonic graphene-based sensor with a microcavity defect channel covered by two graphene layers. Our proposed model introduces an optical contact-free mechanism for the detection of low-concentration molecules attached to graphene's surface. We also show that FR angles could reveal reversal signs for a different amount of surface transfer doping.