Giant terahertz pulling force within an evanescent field propelled by wave coupling into radiation and bound modes

TL;DR

This paper theoretically demonstrates a tunable terahertz plasmonic tweezer using graphene on a high-index substrate, capable of exerting a giant pulling force on particles via evanescent field coupling and momentum conservation.

Contribution

It introduces a novel graphene-based terahertz tweezer design that leverages polarization-dependent mode coupling for particle manipulation.

Findings

Enhanced rotating polarizability enables directional near-field coupling.

Net force on particles can be opposite to the evanescent field push.

Potential for new photonic devices based on nanoparticle-mode interactions.

Abstract

Manipulation of subwavelength objects by engineering the electromagnetic waves in the environment medium is pivotal for several particle handling techniques. In this letter, we theoretically demonstrate the possibility of engineering a compact and tunable plasmon-based terahertz tweezer using a graphene monolayer that is deposited on a high-index substrate. Under total-internal-reflection illumination, such device is shown to be capable of inducing an enhanced rotating polarizability thus enabling directional near-field coupling into the graphene plasmon mode and radiation modes in the substrate. As a result of the total momentum conservation, the net force exerted on the particle points in a direction opposite to the pushing force of the exciting evanescent field. Our results can contribute to novel realizations of photonic devices based on polarization dependent interactions between nanoparticles and electromagnetic mode fields.