1,227 research outputs found
Tuning the electromagnetic local density of states in graphene-covered systems via strong coupling with graphene plasmons
It is known that the near-field spectrum of the local density of states of
the electromagnetic field above a SiC/air interface displays an intense narrow
peak due to the presence of a surface polariton. It has been recently shown
that this surface wave can be strongly coupled with the sheet plasmon of
graphene in graphene-SiC heterosystems. Here, we explore the interplay between
these two phenomena and demonstrate that the spectrum of the electromagnetic
local density of states in these systems presents two peaks whose position
depends dramatically both on the distance to the interface and on the chemical
potential of graphene. This paves the way towards the active control of the
local density of states.Comment: 6 pages, 4 figure
Graphene-plasmon polaritons: From fundamental properties to potential applications
With the unique possibilities for controlling light in nanoscale devices,
graphene plasmonics has opened new perspectives to the nanophotonics community
with potential applications in metamaterials, modulators, photodetectors, and
sensors. This paper briefly reviews the recent exciting progress in graphene
plasmonics. We begin with a general description for optical properties of
graphene, particularly focusing on the dispersion of graphene-plasmon
polaritons. The dispersion relation of graphene-plasmon polaritons of spatially
extended graphene is expressed in terms of the local response limit with
intraband contribution. With this theoretical foundation of graphene-plasmon
polaritons, we then discuss recent exciting progress, paying specific attention
to the following topics: excitation of graphene plasmon polaritons,
electron-phonon interactions in graphene on polar substrates, and tunable
graphene plasmonics with applications in modulators and sensors. Finally, we
seek to address some of the apparent challenges and promising perspectives of
graphene plasmonics.Comment: Invited minireview paper on graphene plasmon polaritons, 11 pages, 4
figure
Enhancement and tunability of near-field radiative heat transfer mediated by surface plasmon polaritons in thin plasmonic films
The properties of thermal radiation exchange between hot and cold objects can
be strongly modified if they interact in the near field where electromagnetic
coupling occurs across gaps narrower than the dominant wavelength of thermal
radiation. Using a rigorous fluctuational electrodynamics approach, we predict
that ultra-thin films of plasmonic materials can be used to dramatically
enhance near-field heat transfer. The total spectrally integrated film-to-film
heat transfer is over an order of magnitude larger than between the same
materials in bulk form and also exceeds the levels achievable with polar
dielectrics such as SiC. We attribute this enhancement to the significant
spectral broadening of radiative heat transfer due to coupling between surface
plasmon polaritons (SPPs) on both sides of each thin film. We show that the
radiative heat flux spectrum can be further shaped by the choice of the
substrate onto which the thin film is deposited. In particular, substrates
supporting surface phonon polaritons (SPhP) strongly modify the heat flux
spectrum owing to the interactions between SPPs on thin films and SPhPs of the
substrate. The use of thin film phase change materials on polar dielectric
substrates allows for dynamic switching of the heat flux spectrum between
SPP-mediated and SPhP-mediated peaks.Comment: 25 pages, 11 figure
Flatland plasmonics and nanophotonics based on graphene and beyond
In this paper, we review and discuss how the recently discovered two-dimensional (2D) Dirac materials, particularly graphene, may be utilized as new efficient platforms for excitations of propagating and localized surface plasmon polaritons (SPPs) in the terahertz (THz) and mid-infrared (MIR) regions. The surface plasmon modes supported by the metallic 2D materials exhibit tunable plasmon resonances that are essential, yet missing, ingredients needed for THz and MIR photonic and optoelectronic devices. We describe how the atomically thin graphene monolayer and metamaterial structures based on it may tailor and control the spectral, spatial, and temporal properties of electromagnetic radiation. In the same frequency range, the newly unveiled nonlocal, nonlinear, and nonequilibrium electrodynamics in graphene show a variety of nonlinear and amplifying electromagnetic responses, whose potential applications are yet unexplored. With these 2D material platforms, virtually all plasmonic, optoelectronic, and nonlinear functions found in near-infrared (NIR) and visible devices can be analogously transferred to the long-wavelength regime, even with enhanced tunability and new functionalities. The spectral range from THz to MIR is particularly compelling because of the many spectral fingerprints of key chemical, gas, and biological agents, as well as a myriad of remote sensing, imaging, communication, and security applications
Tunable light-matter interaction and the role of hyperbolicity in graphene-hBN system
Hexagonal boron nitride (hBN) is a natural hyperbolic material which can also
accommodate highly dispersive surface phonon-polariton modes. In this paper, we
examine theoretically the mid-infrared optical properties of graphene-hBN
heterostructures derived from their coupled plasmon-phonon modes. We found that
the graphene plasmon couples differently with the phonons of the two
Reststrahlen bands, owing to their different hyperbolicity. This also leads to
distinctively different interaction between an external quantum emitter and the
plasmon-phonon modes in the two bands, leading to substantial modification of
its spectrum. The coupling to graphene plasmons allows for additional gate
tunability in the Purcell factor, and narrow dips in its emission spectra
Colloquium: Graphene spectroscopy
Spectroscopic studies of electronic phenomena in graphene are reviewed. A
variety of methods and techniques are surveyed, from quasiparticle
spectroscopies (tunneling, photoemission) to methods probing density and
current response (infrared optics, Raman) to scanning probe nanoscopy and
ultrafast pump-probe experiments. Vast complimentary information derived from
these investigations is shown to highlight unusual properties of Dirac
quasiparticles and many-body interaction effects in the physics of graphene.Comment: 36 pages, 16 figure
Plasmonic Properties of Nanoparticle and Two Dimensional Material Integrated Structure
Recently, various groups have demonstrated nano-scale engineering of nanostructures for optical to infrared wavelength plasmonic applications. Most fabrication technique processes, especially those using noble metals, requires an adhesion layer. Previously proposed theoretical work to support experimental measurement often neglect the effect of the adhesion layers. The first finding of this work focuses on the impact of the adhesion layer on nanoparticle plasmonic properties. Gold nanodisks with a titanium adhesion layer are investigated by calculating the scattering, absorption, and extinction cross-section with numerical simulations using a finite difference time domain (FDTD) method. I demonstrate that a gold nanodisk with an adhesive layer significantly shifts the plasmon resonance relative to one without adhesion material. In addition, the adhesive layer also introduces stronger damping and decay time. Next, I investigate the plasmonic properties and effects of dielectric environment of black phosphorene (BP), a newly discovered anisotropic 2D material. Results suggest that the surface plasmon properties of a black phosphorene nanoribbon could be exploited to probe the efficiency of edge plasmonic enhanced absorption. Furthermore, the enhanced absorption of periodic BP nanoribbons is affected strongly by high density free carriers in BP nanoribbon geometries from mid-infrared to high infrared regime. Also when adding a thin dielectric shielding layer, such as hexagonal boron nitride, in addition to preserving the edge mode plasmonic nature of BP, it also allows for an unprecedented control of the absorption resonance energy. Finally, I also show monolayer graphene surface plasmon hybridization with hyperbolic phonon polarization local density of state of hyperbolic ferroelectric LiNbO3. The results show that the dispersion mode hybridization process is significantly regulated by a electrostatic gated single graphene and double graphene layer in addition to the ferroelectric layer size. The spontaneous emission (SE) rate the hyperbolic band contribution of LiNbO3 with graphene integrated system elucidated enhancement and inhibit spontaneous emission. Specially, the SE rate between in hybrid system is always smaller than that of the bulk in the hyperbolic band region with higher chemical potential
The emergence of quantum capacitance in epitaxial graphene
We found an intrinsic redistribution of charge arises between epitaxial
graphene, which has intrinsically n-type doping, and an undoped substrate. In
particular, we studied in detail epitaxial graphene layers thermally elaborated
on C-terminated - (- ()). We have investigated
the charge distribution in graphene-substrate systems using Raman spectroscopy.
The influence of the substrate plasmons on the longitudinal optical phonons of
the substrates has been detected. The associated charge redistribution
reveals the formation of a capacitance between the graphene and the substrate.
Thus, we give for the first time direct evidence that the excess negative
charge in epitaxial monolayer graphene could be self-compensated by the
substrate without initial doping. This induced a previously unseen
redistribution of the charge-carrier density at the substrate-graphene
interface. There a quantum capacitor appears, without resorting to any
intentional external doping, as is fundamentally required for epitaxial
graphene. Although we have determined the electric field existing inside the
capacitor and revealed the presence of a minigap () for
epitaxial graphene on - face terminated carbon, it remains small in
comparison to that obtained for graphene on face terminated . The
fundamental electronic properties found here in graphene on substrates
may be important for developing the next generation of quantum technologies and
electronic/plasmonic devices.Comment: 26 pages, 8 figures, available online as uncorrected proof, Journal
of Materials Chemistry C (2016
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