arXiv subjects

Muamer Kadic

Publications and source records attributed to Muamer Kadic.

50 records · Page 3Linked to original sources

arXiv2016

Optically assisted trapping with high-permittivity dielectric rings: Towards optical aerosol filtration

Controlling the transport, trapping, and filtering of nanoparticles is important for many applications. By virtue of their weak response to gravity and their thermal motion, various physical mechanisms can be exploited for such operations on nanoparticles. However, the manipulation based on optical forces is potentially most appealing since it constitutes a highly deterministic approach. Plasmonic nanostructures have been suggested for this purpose, but they possess the disadvantages of locally generating heat and trapping the nanoparticles directly on surface. Here, we propose the use of dielectric rings made of high permittivity materials for trapping nanoparticles. Thanks to their ability to strongly localize the field in space, nanoparticles can be trapped without contact. We use a semi-analytical method to study the ability of these rings to trap nanoparticles. Results are supported by full-wave simulations. Application of the trapping concept to nanoparticle filtration is suggested.

cond-mat.mtrl-sci↗

arXiv2015

Parallel Hall effect from 3D single-component metamaterials

We propose a class of three-dimensional metamaterial architectures composed of a single doped semiconductor (e.g., n-Si) in air or vacuum that lead to unusual effective behavior of the classical Hall effect. Using an anisotropic structure, we numerically demonstrate a Hall voltage that is parallel---rather than orthogonal---to the external static magnetic-field vector ("parallel Hall effect"). The sign of this parallel Hall voltage can be determined by a structure parameter. Together with the previously demonstrated positive or negative orthogonal Hall voltage, we demonstrate four different sign combinations

physics.class-ph↗

arXiv2015

Hall-effect sign-inversion in a realizable 3D metamaterial

In 2009, Briane and Milton proved mathematically the existence of three-dimensional isotropic metamaterials with a classical Hall coefficient which is negative with respect to that of all of the metamaterial constituents. Here, we significantly simplify their blueprint towards an architecture composed of only a single constituent material in vacuum/air, which can be seen as a special type of porosity. We show that the sign of the Hall voltage is determined by a separation parameter between adjacent tori. This qualitative behavior is robust even for only a small number of metamaterial unit cells. The combination of simplification and robustness brings experimental verifications of this striking sign-inversion into reach.

cond-mat.mtrl-sci↗

arXiv2014

Invisible waveguides on metal plates for plasmonic analogues of electromagnetic wormholes

We introduce two types of toroidal metamaterials which are invisible to surface plasmon polaritons (SPPs) propagating on a metal surface. The former is a toroidal handlebody bridging remote holes on the metal surface: It works as a kind of plasmonic counterpart of electromagnetic wormholes. The latter is a toroidal ring lying on the metal surface: This bridges two disconnected metal surfaces i.e. It connects a thin metal cylinder to a flat metal surface with a hole. Full-wave numerical simulations demonstrate that an electromagnetic field propagating inside these metamaterials does not disturb the propagation of SPPs at the metal surface. A multilayered design of these devices is proposed, based on effective medium theory for a set of reduced parameters: The former plasmonic analogue of electromagnetic wormhole requires homogeneous isotropic magnetic layers, while the latter merely requires dielectric layers.

physics.optics↗

arXiv2014

Pentamode metamaterials with independently tailored bulk modulus and mass density

We propose a class of linear elastic three-dimensional metamaterials for which the effective parameters bulk modulus and mass density can be adjusted independently over a large range|which is not possible for ordinary materials. First, we systematically evaluate the static mechanical properties and the phonon dispersion relations. We show that the two are quantitatively consistent in the long-wavelength limit. To demonstrate the feasibility, corresponding fabricated polymer microstructures are presented. Finally, we discuss calculations for laminates composed of alternating layers of two different metamaterials with equal bulk modulus yet different mass density. This leads to metamaterials with effectively anisotropic uniaxial dynamic mass density tensors.

cond-mat.mtrl-sci↗

arXiv2013

Elastic measurements on macroscopic three-dimensional pentamode metamaterials

Pentamode metamaterials approximate tailorable artificial liquids. Recently, microscopic versions of these intricate three-dimensional structures have been fabricated, but direct experimental characterization has not been possible yet. Here, using three-dimensional printing, we fabricate macroscopic polymer-based samples with many different combinations of the small connection diameter $d$ and the lattice constant $a$. Direct measurements of the static shear modulus and the Young's modulus reveal that both scale approximately according to $(d/a)^3$, in good agreement with continuum-mechanics calculations. For the smallest accessible values of $d/a \approx 1.5\%$, we find derived ratios of bulk modulus $B$ to shear modulus $G$ of $B/G \approx 1000$.

cond-mat.mtrl-sci↗

arXiv2013

On three-dimensional dilational elastic metamaterials

Dilational materials are stable three-dimensional isotropic auxetics with an ultimate Poisson's ratio of -1. We design, evaluate, fabricate, and characterize crystalline metamaterials approaching this ideal. To reveal all modes, we calculate the phonon band structures. On this basis, using cubic symmetry, we can unambiguously retrieve all different non-zero elements of the rank-4 effective metamaterial elasticity tensor, from which all effective elastic metamaterial properties follow. While the elastic properties and the phase velocity remain anisotropic, the effective Poisson's ratio indeed becomes isotropic and approaches -1 in the limit of small internal connections. This finding is also supported by independent static continuum-mechanics calculations. In static experiments on macroscopic polymer structures fabricated by three-dimensional printing, we measure Poisson's ratios as low as -0.8 in good agreement with theory. Microscopic samples are also presented.

cond-mat.mtrl-sci↗

arXiv2013

Experiments on transformation thermodynamics: Molding the flow of heat

It has recently been shown theoretically that the time-dependent heat conduction equation is form-invariant under curvilinear coordinate transformations. Thus, in analogy to transformation optics, fictitious transformed space can be mapped onto (meta-)materials with spatially inhomogeneous and anisotropic heat-conductivity tensors in the laboratory space. On this basis, we design, fabricate, and characterize a micro-structured thermal cloak that molds the flow of heat around an object in a metal plate. This allows for transient protection of the object from heating, while maintaining the same downstream heat flow as without object and cloak.

cond-mat.mtrl-sci↗

arXiv2012

Phonon band structures of three-dimensional pentamode metamaterials

Three-dimensional pentamode metamaterials are artificial solids that approximately behave like liquids, which have vanishing shear modulus. Pentamodes have recently become experimental reality. Here, we calculate their phonon band structures for various parameters. Consistent with static continuum mechanics, we find that compression and shear waves exhibit phase velocities that can realistically be different by more than one order of magnitude. Interestingly, we also find frequency intervals with more than two octaves bandwidth in which pure single-mode behavior is obtained. Herein, exclusively compression waves exist due to a complete three-dimensional band gap for shear waves and, hence, no coupling to shear modes is possible. Such single-mode behavior might, e.g., be interesting for transformation-elastodynamics architectures.

cond-mat.mtrl-sci↗

arXiv2012

On the feasibility of pentamode mechanical metamaterials

Conceptually, all conceivable three-dimensional mechanical materials can be built from pentamode materials. Pentamodes also enable to implement three-dimensional transformation acoustics - the analogue of transformation optics. However, pentamodes have not been realized experimentally to the best of our knowledge. Here, we investigate inasmuch the pentamode theoretical ideal suggested by Milton and Cherkaev in 1995 can be approximated by a metamaterial with current state-of-the-art lithography. Using numerical calculations calibrated by our fabricated three-dimensional microstructures, we find that the figure of merit, i.e., the ratio of bulk modulus to shear modulus, can realistically be made as large as about 1,000.

cond-mat.mtrl-sci↗

arXiv2011

Plasmonic interaction of light with negative index and gold nano-checkerboards

Negative refractive index materials (NRIM) make possible unique effects such as a convergent at lens due to the reversed Snell-Descartes laws of refraction. NRIM are also known to be able to support a host of surface plasmon states for both polarizations of light which are responsible for the sub-wavelength image resolution achieved by a slab of NRIM. A generalized lens theorem provides us with a class of spatially varying slab lenses satisfying the prerequisite symmetries to fold the optical space onto itself. This theorem can be derived using powerful tools of transformational optics. A paradigm of such complementary media are checkerboards consisting of alternating cells of positive and negative refractive index that represent a very singular situation in which the local density of modes at the corners are enormously enhanced. We have considered several theoretical and numerical aspects of such structured films including a finite slabs of multi-scale checkerboards of NRIM satisfying the generalized lens theorem which are host of strongly enhanced electromagnetic feld. Such checkerboards can be mapped using transformational optics onto three-dimensional corner lenses consisting of semi-infinite heterogeneous anisotropic regions of space satisfying the generalized lens theorem. It is also possible to design three-dimensional checkerboards of complementary media, the only restriction being that corresponding unfolded structures in the plane are constrained by the four color theorem. Some of these meta-surfaces in the plane display thin bridges of complementary media, and this further enhances their plasmonic response. Since plasmonic metals mimic the behaviour of NRIM at small length scales, opaque gold films structured at sub-micron scales in a checkerboard fashion were fabricated using focussed-ion-beam technologies and their scattering spectra measured.

physics.optics↗

arXiv2010

Plasmonic space folding: focussing surface plasmons via negative refraction in complementary media

We extend designs of perfect lenses to the focussing of surface plasmon polaritons (SPPs) propagating at the interface between two anisotropic media of opposite permittivity sign. We identify the role played by the components of anisotropic and heterogeneous tensors of permittivity and permeability, deduced from a coordinate transformation, in the dispersion relation governing propagation of SPPs. We illustrate our theory with three-dimensional finite element computations for focussing of SPPs by perfect flat and cylindrical lenses.

physics.optics↗

arXiv2010

Controlling surface plasmon polaritons in transformed coordinates

Transformational optics allow for a markedly enhanced control of the electromagnetic wave trajectories within metamaterials with interesting applications ranging from perfect lenses to invisibility cloaks, carpets, concentrators and rotators. Here, we present a review of curved anisotropic heterogeneous meta-surfaces designed using the tool of transformational plasmonics, in order to achieve a similar control for surface plasmon polaritons in cylindrical and conical carpets, as well as cylindrical cloaks, concentrators and rotators of a non-convex cross-section. Finally, we provide an asymptotic form of the geometric potential for surface plasmon polaritons on such surfaces in the limit of small curvature.

physics.optics↗

arXiv2010

Hidden progress: broadband plasmonic invisibility

The key challenge in current research into electromagnetic cloaking is to achieve invisibility over an extended bandwidth. There has been significant progress towards this using the idea of cloaking by sweeping under the carpet of Li and Pendry, with dielectric structures superposed on a mirror. Here, we show that we can harness surface plasmon polaritons at a metal surface structured with a dielectric material to obtain a unique control of their propagation. We exploit this to control plasmonic coupling and demonstrate both theoretically and experimentally cloaking over an unprecedented bandwidth (650-900 nm). Our non-resonant plasmonic metamaterial allows a curved reflector to mimic a flat mirror. Our theoretical predictions are validated by experiments mapping the surface light intensity at the wavelength 800 nm.

physics.optics↗