502 research outputs found
Graphene-based extremely wide-angle tunable metamaterial absorber
We investigate the absorption properties of graphene-based anisotropic
metamaterial structures where the metamaterial layer possesses an
electromagnetic response corresponding to a near-zero permittivity. We find
that through analytical and numerical studies, near perfect absorption arises
over an unusually broad range of beam incidence angles. Due to the presence of
graphene, the absorption is tunable via a gate voltage, providing dynamic
control of the energy transmission. We show that this strongly enhanced
absorption arises due to a coupling between light and a fast wave-mode
propagating along the graphene/metamaterial hybrid.Comment: 9 pages, 6 figure
Giant optical nonlocality near the Dirac point in metal-dielectric multilayer metamaterials
The giant optical nonlocality near the Dirac point in lossless
metal-dielectric multilayer metamaterials is revealed and investigated through
the analysis of the band structure of the multilayer stack in the
three-dimensional omega-k space, according to the transfer-matrix method with
the optical nonlocal effect. The position of the Dirac point is analytically
located in the omega-k space. It is revealed that the emergence of the Dirac
point is due to the degeneracy of the symmetric and the asymmetric eigenmodes
of the coupled surface plasmon polaritons. The optical nonlocality induced
epsilon-near-zero frequency shift for the multilayer stack compared to the
effective medium is studied. Furthermore, the giant optical nonlocality around
the Dirac point is explored with the iso-frequency contour analysis, while the
beam splitting phenomenon at the Dirac point due to the optical nonlocal effect
is also demonstrated.Comment: 20 pages, 4 figure
Epsilon-Near-Zero Grids for On-chip Quantum Networks
Realization of an on-chip quantum network is a major goal in the field of
integrated quantum photonics. A typical network scalable on-chip demands
optical integration of single photon sources, optical circuitry and detectors
for routing and processing of quantum information. Current solutions either
notoriously experience considerable decoherence or suffer from extended
footprint dimensions limiting their on-chip scaling. Here we propose and
numerically demonstrate a robust on-chip quantum network based on an
epsilon-near-zero (ENZ) material, whose dielectric function has the real part
close to zero. We show that ENZ materials strongly protect quantum information
against decoherence and losses during its propagation in the dense network. As
an example, we model a feasible implementation of an ENZ network and
demonstrate that quantum information can be reliably sent across a titanium
nitride grid with a coherence length of 434 nm, operating at room temperature,
which is more than 40 times larger than state-of-the-art plasmonic analogs. Our
results facilitate practical realization of large multi-node quantum photonic
networks and circuits on-a-chip.Comment: 13 pages, 5 figure
Cooperative behavior of quantum dipole emitters coupled to a zero-index nanoscale waveguide
We study cooperative behavior of quantum dipole emitters coupled to a
rectangular waveguide with dielectric core and silver cladding. We investigate
cooperative emission and inter-emitter entanglement generation phenomena for
emitters whose resonant frequencies are near the frequency cutoff of the
waveguide, where the waveguide effectively behaves as zero-index metamaterial.
We show that coupling emitters to a zero-index waveguide allows one to relax
the constraint on precision positioning of emitters for observing inter-emitter
entanglement generation and extend the spatial scale at which the superradiance
can be observed
Active and Fast Tunable Plasmonic Metamaterials
Active and Fast Tunable Plasmonic Metamaterials is a research development that has contributed to studying the interaction between light and matter, specifically focusing on the interaction between the electromagnetic field and free electrons in metals. This interaction can be stimulated by the electric component of light, leading to collective oscillations. In the field of nanotechnology, these phenomena have garnered significant interest due to their ability to enable the transmission of both optical signals and electric currents through the same thin metal structure. This presents an opportunity to connect the combined advantages of photonics and electronics within a single platform. This innovation gives rise to a new subfield of photonics known as plasmonic metamaterials.Plasmonic metamaterials are artificial engineering materials whose optical properties can be engineered to generate the desired response to an incident electromagnetic wave. They consist of subwavelength-scale structures which can be understood as the atoms in conventional materials. The collective response of a randomly or periodically ordered ensemble of such meta-atoms defines the properties of the metamaterials, which can be described in terms of parameters such as permittivity, permeability, refractive index, and impedance. At the interface between noble metal particles and dielectric media, collective oscillations of the free electrons in the metal particles can be resonantly excited, known as plasmon resonances. This work considered two plasmon resonances: localised surface plasmon resonances (LSPRs) and propagating surface plasmon polaritons (SPPs).The investigated plasmonic metamaterials, designed with specific structures, were considered for use in various applications, including telecommunications, information processing, sensing, industry, lighting, photovoltaic, metrology, and healthcare. The sample structures are manufactured using metal and dielectric materials as artificial composite materials. It can be used in the electromagnetic spectrum's visible and near-infrared wavelength range. Results obtained proved that artificial composite material can produce a thermal coherent emission at the mid-infrared wavelength range and enable active and fast-tunable optoelectronic devices. Therefore, this work focused on the integrated thermal infrared light source platforms for various applications such as thermal analysis, imaging, security, biosensing, and medical diagnosis. Enabled by Kirchhoff's law of thermal radiation, this work combined the concepts of material absorption with material emission. Hence, the results obtained proved that this approach enhances the overall performance of the active and fast-tunable plasmonic metamaterial in terms of with effortless and fast tunability. This work further considers the narrow line width of the coherent thermal emission, tunable emission, and angular tunable emission at the mid-infrared, which are achieved through plasmonic stacked grating structure (PSGs) and plasmonic infrared absorber structure (PIRAs).Three-dimensional (3D) plasmonic stacked gratings (PSGs) was used to create a tunable plasmonic metamaterial at optical wavelengths ranging from 3 m to 6 m, and from 6m to 9 m. These PSGs are made of a metallic grating with corrugations caused by narrow air openings, followed by a Bragg grating (BG). Additionally, this work demonstrated a thermal radiation source customised for the mid-infrared wavelength range of 3 μm to 5 μm. This source exhibits intriguing characteristics such as high emissivity, narrowband spectra, and sharp angular response capabilities. The proposed thermal emitter consists of a two-dimensional (2D) metallic grating on top of a one-dimensional dielectric BG.Results obtained presented a plasmonic infrared absorber (PIRA) graphene nanostructure designed for a wavelength range of 3 to 14 μm. It was observed and concluded that this wavelength range offers excellent opportunities for detection, especially when targeting gas molecules in the infrared atmospheric windows. The design framework is based on active plasmon control for subwavelength-scale infrared absorbers within the mid-infrared range of the electromagnetic spectrum. Furthermore, this design is useful for applications such as infrared microbolometers, infrared photodetectors, and photovoltaic cells.Finally, the observation and conclusion drawn for the sample of nanostructure used in this work, which consists of an artificial composite arrangement with plasmonic material, can contribute to a highly efficient mid-infrared light source with low power consumption, fast response emissions, and is a cost-effective structure
Experimental demonstration of tunable graphene-polaritonic hyperbolic metamaterial
Tuning the macroscopic dielectric response on demand holds potential for actively tunable metaphotonics and optical devices. In recent years, graphene has been extensively investigated as a tunable element in nanophotonics. Significant theoretical work has been devoted on the tuning the hyperbolic properties of graphene/dielectric heterostructures; however, until now, such a motif has not been demonstrated experimentally. Here we focus on a graphene/polaritonic dielectric metamaterial, with strong optical resonances arising from the polar response of the dielectric, which are, in general, difficult to actively control. By controlling the doping level of graphene via external bias we experimentally demonstrate a wide range of tunability from a Fermi level of E_F=0 eV to E_F=0.5 eV, which yields an effective epsilon-near-zero crossing and tunable dielectric properties, verified through spectroscopic ellipsometry and transmission measurements
Plasmon Resonance in Multilayer Graphene Nanoribbons
Plasmon resonance in nanopatterned single layer graphene nanoribbon (SL-GNR),
double layer graphene nanoribbon (DL-GNR) and triple layer graphene nanoribbon
(TL-GNR) structures is studied both experimentally and by numerical
simulations. We use 'realistic' graphene samples in our experiments to identify
the key bottle necks in both experiments and theoretical models. The existence
of electrical tunable plasmons in such stacked multilayer GNRs was first
experimentally verified by infrared microscopy. We find that the strength of
the plasmonic resonance increases in DL-GNR when compared to SL-GNRs. However,
we do not find a further such increase in TL-GNRs compared to DL-GNRs. We
carried out systematic full wave simulations using finite element technique to
validate and fit experimental results, and extract the carrier scattering rate
as a fitting parameter. The numerical simulations show remarkable agreement
with experiments for unpatterned SLG sheet, and a qualitative agreement for
patterned graphene sheet. We believe that further improvements such as
introducing a bandgap into the numerical model could lead to a better
quantitative agreement of numerical simulations with experiments. We also note
that such advanced modeling would first require better quality graphene samples
and accurate measurements
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