Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMagnetic hyperbolic metamaterial of polaritonic nanowires
129
0
0.0
(
0
)
Added by
Mohammad Sajjad Mirmoosa
Publication date
2016
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We show that the axial component of the magnetic permeability tensor is resonant for a wire medium consisting of high-index epsilon-positive nanowires, and its real part changes the sign at a certain frequency. At this frequency the medium experiences the topological transition from the hyperbolic to the elliptic type of dispersion. We show that the transition regime is characterized by extremely strong dependence of the permeability on the wave vector. This implies very high density of electromagnetic states that results in the filamentary pattern and noticeable Purcell factor for a transversely oriented magnetic dipole.
rate research
Read More
Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. In such materials light propagation is unusual, leading to novel and often non-intuitive optical phenomena. Here we report infrared nano-imaging experiments demonstrating that crystals of hexagonal boron nitride (hBN), a natural mid-infrared hyperbolic material, can act as a hyper-focusing lens and as a multi-mode waveguide. The lensing is manifested by subdiffractional focusing of phonon-polaritons launched by metallic disks underneath the hBN crystal. The waveguiding is revealed through the modal analysis of the periodic patterns observed around such launchers and near the sample edges. Our work opens new opportunities for anisotropic layered insulators in infrared nanophotonics complementing and potentially surpassing concurrent artificial hyperbolic materials with lower losses and higher optical localization.
Hexagonal boron nitride (h-BN) is a natural hyperbolic material, for which the dielectric constants are the same in the basal plane (epsilon^t = epsilon^x = epsilon^y) but have opposite signs (epsilon^t*epsilon^z < 0) from that in the normal plane (epsilon^z). Due to this property, finite-thickness slabs of h-BN act as multimode waveguides for propagation of hyperbolic phonon polaritons - collective modes that originate from the coupling between photons and electric dipoles in phonons. However, control of these hyperbolic phonon polaritons modes has remained challenging, mostly because their electrodynamic properties are dictated by the crystal lattice of h-BN. Here we show by direct nano-infrared imaging that these hyperbolic polaritons can be effectively modulated in a van der Waals heterostructure composed of monolayer graphene on h-BN. Tunability originates from the hybridization of surface plasmon polaritons in graphene with hyperbolic phonon polaritons in h-BN, so that the eigenmodes of the graphene/h-BN heterostructure are hyperbolic plasmon-phonon polaritons. Remarkably, the hyperbolic plasmon-phonon polaritons in graphene/h-BN suffer little from ohmic losses, making their propagation length 1.5-2.0 times greater than that of hyperbolic phonon polaritons in h-BN. The hyperbolic plasmon-phonon polaritons possess the combined virtues of surface plasmon polaritons in graphene and hyperbolic phonon polaritons in h-BN. Therefore, graphene/h-BN structures can be classified as electromagnetic metamaterials since the resulting properties of these devices are not present in its constituent elements alone.
The optical properties of some nanomaterials can be controlled by an external magnetic field, providing active functionalities for a wide range of applications, from single-molecule sensing to nanoscale nonreciprocal optical isolation. Materials with broadband tunable magneto-optical response are therefore highly desired for various components in next-generation integrated photonic nanodevices. Concurrently, hyperbolic metamaterials received a lot of attention in the past decade since they exhibit unusual properties that are rarely observed in nature and provide an ideal platform to control the optical response at the nanoscale via careful design of the effective permittivity tensor, surpassing the possibilities of conventional systems. Here, we experimentally study magnetic circular dichroism in a metasurface made of type-II hyperbolic nanoparticles on a transparent substrate. Numerical simulations confirm the experimental findings, and an analytical model is established to explain the physical origin of the observed magneto-optical effects, which can be described in terms of the coupling of fundamental electric and magnetic dipole modes with an external magnetic field. Our system paves the way for the development of nanophotonic active devices combining the benefits of sub-wavelength light manipulation in hyperbolic metamaterials supporting a large density of optical states with the ability to freely tune the magneto-optical response via control over the anisotropic permittivity of the system.
We propose a review of the current knowledge about the synthesis, magnetic properties and applications of magnetic cylindrical nanowires and nanotubes. By nano we consider diameters reasonably smaller than a micrometer. At this scale, comparable to micromagnetic and transport length scales, novel properties appear. At the same time, this makes the underlying physics easier to understand due to the limiter number of degrees of freedom involved. The three-dimensional nature and the curvature of these objects contribute also to their specific properties, compared to patterns flat elements. While the topic of nanowires and later nanotubes started now decades ago, it is nevertheless flourishing, thanks to the progress of synthesis, theory and characterization tools. These give access to ever more complex and thus functional structures, and also shifting the focus from material-type measurements of large assemblies, to single-object investigations. We first provide an overview of common fabrication methods yielding nanowires, nanotubes and structures engineered in geometry~(change in diameter, shape) or material (segments, core-shell structures), shape or core-shell. We then review their magnetic properties: global measurements, magnetization states and switching, single domain wall statics and dynamics, and spin waves. For each aspect, both theory and experiments are surveyed. We also mention standard characterization techniques useful for these. We finally mention emerging applications of magnetic nanowires and nanotubes, along with the foreseen perspectives in the topic.
In this work, we demonstrate a self-standing bulk three-dimensional metamaterial based on the network of silver nanowires in an alumina membrane. This constitutes an anisotropic effective medium with hyperbolic dispersion, which can be used in sub-diffraction imaging or optical cloaks. Highly anisotropic dielectric constants of the material range from positive to negative, and the transmitted laser beam shifts both toward the normal to the surface, as in regular dielectrics, and off the normal, as in anisotropic dielectrics with the refraction index smaller than one. The designed photonic metamaterial is the thickest reported in the literature, both in terms of its physical size 1cm x 1cm x 51 mm, and the number of vacuum wavelengths, N=61 at l=0.84 mm.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
