Optical activity in graphene-based cylindrical plasmonic waveguides

Nowadays, graphene plasmonics shows a great number of features unusual for conventional (metal-based) plasmonics: from the strong energy localization and the large propagation distance of surface plasmon-polaritons (SPPs) due... [ view full abstract ]

Nowadays, graphene plasmonics shows a great number of features unusual for conventional (metal-based) plasmonics: from the strong energy localization and the large propagation distance of surface plasmon-polaritons (SPPs) due to the existence of both TE- and TM- polarized modes to the possibility of control SPPs by tuning the graphene chemical potential (or, equivalently, the applied gate voltage or chemical doping) [1, 2]. Cylindrical graphene-based plasmonic structures have some advantages as compared to the planar geometry: reduced edge losses, existence of high-order azimuthal modes, etc [3, 4].

In this work, we discuss novel ways to obtain an optical activity in cylindrical graphene-based plasmonic structures and their possible applications in plasmonics. Recently, we have shown that the magneto-optical activity (or gyrotropy) of a dielectric nanowire covered with graphene leads to the giant Faraday rotation of the electric field distribution of high-order plasmonic modes propagating along the wire [5]. This effect is mediated by the magneto-optical activity in the bulk of the dielectric wire. An alternative way to create an optical activity at the surface arises from engineering of chiral graphene-based plasmonic waveguides. The spiral graphene-based nanostructures demonstrate a strong surface-induced optical activity, where the rotation of high-order plasmonic modes is comparable or even larger than in gyrotropic graphene-covered nanowires. The sensitivity of the chirality to the applied strain suggests an application of graphene-based waveguides as strain sensors.
Moreover, the control of the electromagnetic field intensity at the nanoscale in graphene-based plasmonic structures may open the door to novel applications in quantum plasmonics.

This work was supported in part by RFBR (grants ## 16-37-00023, 16-07-00751, 16-29-14045) and RScF (grant # 14-22-00279).
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