Maxim L. Nesterov

Transformation optics for plasmonics

A new strategy to control the flow of surface plasmon polaritons at metallic surfaces is presented. It is based on the application of the concept of transformation optics to devise the optical parameters of the dielectric medium placed on top of the metal surface. We describe the general methodology for the design of transformation optical devices for surface plasmons and analyze, for proof-of-principle purposes, three representative examples with different functionalities: a beam shifter, a cylindrical cloak, and a ground-plane cloak.

Domino plasmons for subwavelength terahertz circuitry.

A new approach for the spatial and temporal modulation of electromagnetic fields at terahertz frequencies is presented. The waveguiding elements are based on plasmonic and metamaterial notions and consist of an easy-to-manufacture periodic chain of metallic box-shaped elements protruding out of a metallic surface. It is shown that the dispersion relation of the corresponding electromagnetic modes is rather insensitive to the waveguide width, preserving tight confinement and reasonable absorption loss even when the waveguide transverse dimensions are well in the subwavelength regime. This property enables the simple implementation of key devices, such as tapers and power dividers. Additionally, directional couplers, waveguide bends, and ring resonators are characterized, demonstrating the flexibility of the proposed concept and the prospects for terahertz applications requiring high integration density.

Graphene supports the propagation of subwavelength optical solitons

Nonlinear propagation of light in a graphene mono- layer is studied theoretically. It is shown how the large intrin- sic nonlinearity of graphene at optical frequencies enables the formation of quasi one-dimensional self-guided beams (spatial solitons) featuring subwavelength widths at moderate electric- field peak intensities. A novel class of nonlinear self-confined modes resulting from the hybridization of surface plasmon po- laritons with graphene optical solitons is also demonstrated.

Strong Plasmon Reflection at Nanometer-Size Gaps in Monolayer Graphene on SiC

We employ tip-enhanced infrared near-field microscopy to study the plasmonic properties of epitaxial quasi-free-standing monolayer graphene on silicon carbide. The near-field images reveal propagating graphene plasmons, as well as a strong plasmon reflection at gaps in the graphene layer, which appear at the steps between the SiC terraces. When the step height is around 1.5 nm, which is two orders of magnitude smaller than the plasmon wavelength, the reflection signal reaches 20% of its value at graphene edges, and it approaches 50% for step heights as small as 5 nm. This intriguing observation is corroborated by numerical simulations and explained by the accumulation of a line charge at the graphene termination. The associated electromagnetic fields at the graphene termination decay within a few nanometers, thus preventing efficient plasmon transmission across nanoscale gaps. Our work suggests that plasmon propagation in graphene-based circuits can be tailored using extremely compact nanostructures, such as ultranarrow gaps. It also demonstrates that tip-enhanced near-field microscopy is a powerful contactless tool to examine nanoscale defects in graphene.

Geometrically induced modification of surface plasmons in the optical and telecom regimes

We demonstrate that the introduction of a subwavelength periodic modulation into a metallic structure strongly modifies the guiding characteristics of the surface plasmon modes supported by the system. Moreover, it is also shown how a new type, to our knowledge, of a tightly confined surface plasmon polariton mode can be created by just milling a periodic corrugation into a metallic ridge placed on top of a metal surface.

Moulding the flow of surface plasmons using conformal and quasiconformal mappings

In this paper we analyze how Transformation Optics recipes can be applied to control the flow of surface plasmons on metal-dielectric interfaces. We study in detail five different examples: a cylindrical cloak, a beam shifter, a right-angle bend, a lens and a ground-plane cloak. First, we demonstrate that only the modification of the electric permittivity and magnetic permeability in the dielectric side can lead to almost perfect functionalities for surface plasmons. We also show that, thanks to the quasi two-dimensional character of surface plasmons and its inherent polarization, the application of conformal and quasiconformal mapping techniques allows the design of plasmonic devices in which only the isotropic refractive index of the dielectric film needs to be engineered.

Resonance effects due to exitation of the surface waves in periodically-modulated layered superconductors

In this paper the surface Josephson plasma wave (SJPW) excitation on the periodically-modulated layered superconductor is considered. It is shown that the absorption of the incident electromagnetic wave can be substantially increased at certain incident angles due to the resonance excitation of the surface waves. The optimal combinations of the parameters of the problem (modulation amplitude, wavelength, incident angle) corresponding to maximum SJPW excitation and the effect of the total suppression of specular reflection (TSSR) are found for a real medium (Bi2212).

Surface Josephson Plasma Waves in Layered HTC Superconductors and their Excitation via Attenuated Total Reflection

The detailed theoretical analysis of the resonance phenomena caused by excitation of the surface Josephson plasma waves (SJPW) in layered superconductors is made. It is shown that the surface waves at the boundary between the vacuum and layered superconductor can be excited by attenuated total reflection (ATR). The dispersion relation for the SJPW and the intensity of the reflected wave are investigated. The parameters of the problem (optimal thickness of vacuum layer, optimal wavelength) corresponding to the total suppression of specular reflection (TSSR) are found