67 research outputs found
Enhanced Optical Dichroism of Graphene Nanoribbons
The optical conductivity of graphene nanoribbons is analytical and exactly
derived. It is shown that the absence of translation invariance along the
transverse direction allows considerable intra-band absorption in a narrow
frequency window that varies with the ribbon width, and lies in the THz range
domain for ribbons 10-100nm wide. In this spectral region the absorption
anisotropy can be as high as two orders of magnitude, which renders the medium
strongly dichroic, and allows for a very high degree of polarization (up to
~85) with just a single layer of graphene. The effect is resilient to level
broadening of the ribbon spectrum potentially induced by disorder. Using a
cavity for impedance enhancement, or a stack of few layer nanoribbons, these
values can reach almost 100%. This opens a potential prospect of employing
graphene ribbon structures as efficient polarizers in the far IR and THz
frequencies.Comment: Revised version. 10 pages, 7 figure
Tunable graphene-based polarizer
It is shown that an attenuated total reflection structure containing a
graphene layer can operate as a tunable polarizer of the electromagnetic
radiation. The polarization angle is controlled by adjusting the voltage
applied to graphene via external gate. The mechanism is based on the resonant
coupling of polarized electromagnetic waves to the surface
plasmon-polaritons in graphene. The presented calculations show that, at
resonance, the reflected wave is almost 100% polarized.Comment: submitted to the Applied Physics Letter
Graphene-based polaritonic crystal
It is shown that monolayer graphene deposited on a spatially-periodic gate
behaves as a polaritonic crystal. Its band structure depending on the applied
gate voltage is studied. The scattering of electromagnetic radiation from such
a crystal is presented calculated and analyzed in terms of Fano-type resonances
between the reflected continuum and plasmon-polariton modes forming narrow
bands.Comment: submitted to Phys. Rev. Let
Mechanism for graphene-based optoelectronic switches by tuning surface plasmon-polaritons in monolayer graphene
It is shown that one can explore the optical conductivity of graphene,
together with the ability of controlling its electronic density by an applied
gate voltage, in order to achieve resonant coupling between an external
electromagnetic radiation and surface plasmon-polaritons in the graphene layer.
This opens the possibility of electrical control of the intensity of light
reflected inside a prism placed on top of the graphene layer, by switching
between the regimes of total reflection and total absorption. The predicted
effect can be used to build graphene-based opto-electronic switches.Comment: 5 page
Light scattering by a medium with a spatially modulated optical conductivity: the case of graphene
We describe light scattering from a graphene sheet having a modulated optical
conductivity. We show that such modulation enables the excitation of surface
plasmon-polaritons by an electromagnetic wave impinging at normal incidence.
The resulting surface plasmon-polaritons are responsible for a substantial
increase of electromagnetic radiation absorption by the graphene sheet. The
origin of the modulation can be due either to a periodic strain field or to
adatoms (or absorbed molecules) with a modulated adsorption profile.Comment: http://iopscience.iop.org/0953-8984/24/24/24530
Excitation of localized graphene plasmons by a metallic slit
In this paper we show that graphene surface plasmons can be excited when an electromagnetic wave packet impinges on a single metal slit covered with graphene. The excitation of the plasmons localized over the slit is revealed by characteristic peaks in the absorption spectrum. It is shown that the position of the peaks can be tuned either by the graphene doping level or by the dielectric function of the material filling the slit. The whole system forms the basis for a plasmonic sensor when the slit is filled with an analyte.The authors are grateful for useful discussions with H. Crespo. The authors acknowledge support from the European Commission through the project "Graphene-Driven Revolutions in ICT and Beyond" (Ref. No. 881603), and the Portuguese Foundation for Science and Technology through the Strategic Funding UID/FIS/04650/2019. Additionally, the authors acknowledge financing from FEDER and the Portuguese Foundation for Science and Technology (FCT) through Project No. POCI-01-0145-FEDER-028114
Strongly coupled magnon-plasmon polaritons in graphene- 2D ferromagnet heterostructures
Magnons and plasmons are two very different types of collective modes, acting
on the spin and charge degrees of freedom, respectively. At first sight, the
formation of hybrid plasmon-magnon polaritons in heterostructures of plasmonic
and magnetic systems would face two challenges, the small mutual interaction,
via Zeeman coupling of the electromagnetic field of the plasmon with the spins,
and the energy mismatch, as in most systems plasmons have energies in the eV
range, orders of magnitude larger than magnons. Here we show that graphene
plasmons form polaritons with the magnons of two-dimensional ferrromagnetic
insulators, placed up to to half a micron apart, with Rabi couplings in the
range of 100 GHz (dramatically larger than cavity QED magnonics). This strong
coupling is facilitated both by the small energy of graphene plasmons and the
cooperative super-radiant nature of the plasmon-magnon coupling afforded by
phase matching. We show that the Rabi coupling can be modulated both
electrically and mechanically and we propose a attenuated total internal
reflection experiment to implement ferromagnetic resonance experiments on 2D
ferromagnets driven by plasmon excitation.Comment: 7 pages, 3 figures, appendi
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