It is known that bulk metallic samples reflect microwaves while powdered samples can absorb such radiation and be heated efficiently. In the present work we studied heating mechanisms of metallic powders in a multimode 2.45 GHz microwave applicator. The present paper shows direct evidence of penetration of a layer of metallic powder by microwave radiation and provides theoretical explanation of such behavior.The most effectively heated powder is Fe because both eddy current loss (in alternating H-field) and magnetic reversal loss (in alternating E-field) mechanisms act in case of such metal. Diamagnetic metals Sn and Cu are heated better than paramagnetic Ti while Au is also only slightly heated. Cu- and Ni-based metallic glassy powders are also moderately heated. Weak heating of Au powder (which is a noble metal) can be explained by the absence on the particles of the oxide layer (shell), which allows eddy currents flowing through larger area compared to other metals, and reflection mechanism works much better in such case.

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Faraday effect, inverse magnetooptical effects. 2 ABSTRACT. Graphene is a unique material to study fundamental limits of plasmonics. Apart from the ultimate single-layer thickness, its carrier concentration can be tuned by chemical doping or applying an electric field. In this manner the electrodynamic properties of graphene can be varied from highly conductive to dielectric. Graphene supports strongly confined, propagating surface plasmon-polaritons (SPPs) in a broad spectral range from terahertz to midinfrared frequencies. It also possesses a strong magneto-optical response and thus provides complimentary architectures to conventional magneto-plasmonics based on magneto-optically active metals or dielectrics. Despite of a large number of review articles devoted to plasmonic properties and applications of graphene, little is known about graphene magneto-plasmonics and topological effects in graphene-based nanostructures, which represent the main subject of this review. We discuss several strategies to enhance plasmonic effects in topologically distinct closed surface landscapes, i.e. graphene nanotubes, cylindric nanocavities and toroidal nanostructures. A novel phenomenon of the strongly asymmetric SPP propagation on chiral meta-structures and fundamental relations between structural and plasmonic topological indices are reviewed. I. IntroductionGraphene opens up wide prospects for numerous flatland photonic and plasmonic applications [1-7]. Graphene-based waveguides support localized electromagnetic SPP waves, both TE-and TM-polarized [8-16]. Their tight confinement and long propagation length allow for observing strong light-matter interactions in graphene-based structures [17]. Optical properties of graphene transformations give rise to distinct topological indices, which largely determine the properties of plasmonic modes. The interplay of the intrinsic (elliptic versus hyperbolic) topology of SPPs propagating on a flat 2D-meta-surface and the geometrical 3D-topology of nanostructures can induce novel plasmonic effects: a giant azimuthal rotation of intensity distribution of particular SPP modes upon propagation, one-way propagation of SPPs, vanishing of the Fabry-Perot resonances in finite length meta-tubes, unidirectional circulating Mach-Zehnder-like resonances in a meta-torus, etc.Figure 1: (A) An array of densely packed graphene stripes with sub-wavelength periodicity Λ forms a metasurface which may support both elliptic (B) and hyperbolic SPPs (C). A rolled-up meta-surface forms a meta-tube and its donut-like shape is a meta-torus (D). In (B) and (C) Λ = 50 nm, A = 45 nm, B = 5 nm. 5The cylindrical geometry deserves a particular attention as it provides a common basis for plasmonics in chiral media [38][39][40][41][42] and non-reciprocal magneto-optics in waveguides. It is known that the parallel external magnetic field can rotate a spatially inhomogeneous intensity distribution (i.e. speckle-pattern) of light in the cross-section plane upon its propagation along an optical fiber [43][44][45][46]. Rec...

Transverse-electric (TE) surface plasmons (SPs) are very unusual for plasmonics phenomenon. Graphene proposes a unique possibility to observe these plasmons. Due to transverse motion of carriers, TE SPs speed is usually close to bulk light one. In this work we discuss conditions of TE SPs propagation in cylindrical graphene-based waveguides. We found that the negativity of graphene conductivity’s imaginary part is not a sufficient condition. The structure supports TE SPs when the core radius of waveguide is larger than the critical value Rcr. Critical radius depends on the light frequency and the difference of permittivities inside and outside the waveguide. Minimum value of Rcr is comparable with the wavelength of volume wave and corresponds to interband carriers transition in graphene. We predict that use of multilayer graphene will lead to decrease of critical radius. TE SPs speed may differ more significantly from bulk light one in case of epsilon-near-zero core and shell of the waveguide. Results may open the door for practical applications of TE SPs in optics, including telecommunications.