Programa de Pós-Graduação em Física da UFSC, Florianópolis

Seminário com o Mikhail Igorevich Vasilevskiy – 18 de junho de 2015 – 10h15min

15/06/2015 10:15

O PROGRAMA DE PÓS-GRADUAÇÃO EM FÍSICA convida para o seminário:

GRAPHENE-BASED NANOSTRUCTURES: PLASMONICS IN THE THZ RANGE*

Mikhail Igorevich Vasilevskiy

Universidade do Minho – Portugal

*Evento de reposição da disciplina seminário

Resumo:

The talk will consist of two parts dedicated, respectively, to linear and non-linear optical properties of graphene in the terahertz (THz) spectral range, related to its unique electronic spectrum (gapless and linear in momentum).

In the first part, surface plasmon-polaritons (SPPs) in graphene will be discussed along with several possible ways of their coupling to propagating electromagnetic waves in the THz range, such as (i) the attenuated total reflection (ATR) method employing a prism, (ii) graphene-based gratings or graphene monolayers with modulated conductivity, (iii) a metallic stripe or a needle tip on top of the graphene layer. Potentially interesting for applications SPP effects, such as switching, modulation and polarization of THz radiation will be considered.

In the second part some effects of the optical non-linearity of the surrounding medium or of graphene itself will be considered, including mixed polariton solitons of TE type, optical bistability of a graphene layer, and lattice solitons in a multilayer stack of graphene sheets.

Supporting figures (can be used for advertising, if necessary)

Fig. 1. Excitation of surface plasmon-polaritons using attenuated total reflection (ATR) scheme (Otto configuration). Both s- and p-polarized modes can be excited in a homogeneous monolayer graphene sheet cladded by two dielectrics with dielectric constants ε1 and ε2 (a). Example of a periodically modulated graphene-based structure with substrate dielectric constant changing in a periodic way along the x axis (b).

Fig. 2. EM radiation coupling to a graphene structure with a periodically modulated dielectric constant of the substrate shown in Fig. 1b for ε₂(x)=3.9×[1+0.2cos(2πx/D)] and d→∞: (a) SPP frequency versus k_x (full curves) and light lines for n =1 and -1 (dashed lines); (b) Reflection coefficient (red solid line) and relative square amplitudes of the n =1 (black dashed line) and n =-1 (blue dashed line) SPP modes. For comparison, the reflectivity of graphene deposited on a uniform substrate is depicted by solid green line; (c) Reflectivity versus frequency and incidence angle; (d) Reflectivity versus gate voltage for fixed ω and θ. Other parameters are: gate voltage V = 50V (panels a, b, c), angle of incidence θ = 20^o (panels a, b, d), ε₃ = 1, D = 20.617 μm.