Hybrid Metal-Graphene Plasmons for Tunable Terahertz Technology

TL;DR

This paper introduces a hybrid graphene-metal plasmonic structure that enables highly tunable terahertz resonances with potential applications in detectors, filters, and modulators, overcoming previous limitations of electrical contact integration.

Contribution

It presents a novel hybrid graphene-metal design that achieves near-maximal tunable terahertz absorption and proposes high-mobility graphene for near-100% transmission, advancing THz device technology.

Findings

Demonstrated resonant absorption close to theoretical maximum in large-area graphene.

Predicted near 100% tunable THz transmission with high mobility graphene.

Provided a structure that integrates tunable plasmonic channels with electrical contacts.

Abstract

Among its many outstanding properties, graphene supports terahertz surface plasma waves -- sub-wavelength charge density oscillations connected with electromagnetic fields that are tightly localized near the surface[1,2]. When these waves are confined to finite-sized graphene, plasmon resonances emerge that are characterized by alternating charge accumulation at the opposing edges of the graphene. The resonant frequency of such a structure depends on both the size and the surface charge density, and can be electrically tuned throughout the terahertz range by applying a gate voltage[3,4]. The promise of tunable graphene THz plasmonics has yet to be fulfilled, however, because most proposed optoelectronic devices including detectors, filters, and modulators[5-10] desire near total modulation of the absorption or transmission, and require electrical contacts to the graphene -- constraints that are difficult to meet using existing plasmonic structures. We report here a new class of plasmon resonance that occurs in a hybrid graphene-metal structure. The sub-wavelength metal contacts form a capacitive grid for accumulating charge, while the narrow interleaved graphene channels, to first order, serves as a tunable inductive medium, thereby forming a structure that is resonantly-matched to an incident terahertz wave. We experimentally demonstrate resonant absorption near the theoretical maximum in readily-available, large-area graphene, ideal for THz detectors and tunable absorbers. We further predict that the use of high mobility graphene will allow resonant THz transmission near 100%, realizing a tunable THz filter or modulator. The structure is strongly coupled to incident THz radiation, and solves a fundamental problem of how to incorporate a tunable plasmonic channel into a device with electrical contacts.