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This paper makes evidence for direct dark mode excitation mechanism in a metasurface structure. The dark mode excitation mechanism is entirely determined by structures' symmetry and does not depend on near-field coupling between elements. In our examples, we consider single element based metasurface composed of two V antennas connected in an anti-symmetric arrangement. Both experimental and modeling results show an efficient excitation of magnetic dipolar mode in such structures. The direct dark mode excitation mechanism provides a design that is more robust with respect to technology imperfections. The considered approach opens promising perspectives for new type of nanostructure designs and greatly relaxes fabrication constraints for the optical domain., Comment: 21 pages, 5 figures

With the explosion of wireless networks and automotive radar systems, there is an acute need for new materials and technologies that would not only minimize the size of these devices, but also enhance their performances. The technique of transformation optics-an innovative approach to produce artificial metamaterials that control electromagnetic waves as if space itself was transformed-provides unique opportunities to reach this goal. In this paper we design, fabricate and characterize a new class of metamaterial capable of transforming the source distribution and radiation pattern of an isotropic microwave emitter. Our findings have considerable implications for the development of new ultradirective antennas with superior performances and compactness compared to conventional antennas operating in the same frequency range., Comment: http://prb.aps.org/abstract/PRB/v83/i15/e155108

Spatial coordinate transformation is a suitable tool for the design of complex electromagnetic structures. In this paper, we define three spatial coordinate transformations which show the possibility of designing a taper between two different waveguides. A parametric study is presented for the three transformations and we propose achievable values of permittivity and permeability that can be obtained with existing metamaterials. The performances of such defined structures are demonstrated by finite element numerical simulations.

Metamaterials have paved the way to unprecedented control of the electromagnetic field1,2. The conjunction with space coordinate transformation has led to a novel "relativity inspired" approach for the control of light propagation. "Invisibility cloak" is the most fascinating proposed devices3,4. However, the realized structures up to now used a graded "metamagnetic" so as to achieve the cloaking function11. Artificial magnetism is however still very challenging to obtain in optics despite the currently promising building blocks13-17, not suited for optical cloaking. We report here the first experimental demonstration of non-magnetic cloak at microwave frequencies by direct mapping of the magnetic field together with the first experimental characterization of a cloak in free space configuration. The diameter of the concealed region is as big as 4.4 in wavelength units, the biggest reported experimentally so far. The principle can be scaled down to optical domain while keeping the compatibility with current nanofabrication technologies., Comment: 6 pages, 3figures

Spatial coordinate transformation is used as a reliable tool to control electromagnetic fields. In this paper, we derive the permeability and permittivity tensors of a metamaterial able to transform an isotropically radiating source into a compact ultradirective antenna in the microwave domain. We show that the directivity of this antenna is competitive with regard to conventional directive antennas horn and reflector antennas, besides its dimensions are smaller. Numerical simulations using finite element method are performed to illustrate these properties. A reduction in the electromagnetic material parameters is also proposed for an easy fabrication of this antenna from existing materials. Following that, the design of the proposed antenna using a layered metamaterial is presented. The different layers are all composed of homogeneous and uniaxial anisotropic metamaterials, which can be obtained from simple metal-dielectric structures. When the radiating source is embedded in the layered metamaterial, a highly directive beam is radiated from the antenna