Lorentz force metamaterial with giant optical magnetoelectric response

We demonstrate the first reconfigurable photonic metamaterial controlled by electrical currents and magnetic fields, providing first practically useful solutions for sub-megahertz and high contrast modulation of metamaterial optical properties

Broadband impedance-matched electromagnetic structured ferrite composite in the megahertz range

Copyright © 2014 AIP PublishingA high refractive-index structured ferrite composite is designed to experimentally demonstrate broadband impedance matching to free-space. It consists of an array of ferrite cubes that are anisotropically spaced, thereby allowing for independent control of the effective complex permeability and permittivity. Despite having a refractive index of 9.5, the array gives less than 1% reflection and over 90% transmission of normally incident radiation up to 70 MHz for one of the orthogonal linear polarisations lying in a symmetry plane of the array. This result presents a route to the design of MHz-frequency ferrite composites with bespoke electromagnetic parameters for antenna miniaturisation.Engineering and Physical Sciences Research Council (EPSRC)DSTLQUEST programm

ANALYSIS OF ENTROPY GENERATION DUE TO MAGNETOHYDRODYNAMIC COUPLE STRESS FLUID

We demonstrate the first reconfigurable photonic metamaterial controlled by electrical currents and magnetic fields, providing first practically useful solutions for sub-megahertz and high contrast modulation of metamaterial optical properties

Resonantly inverted microwave transmissivity threshold of metal grids

Open Access journal© Crown copyright 2009. This work is part funded by the Ministry of Defence and is published with the permission of the Defence Science and Technology Laboratory on behalf of the Controller of HMSO.The microwave transmission of arrays of square patches, each rotated by 45 from the axes of the square lattice on which they are positioned, has been experimentally studied as a function of metal occupancy. At low frequencies, the microwave transmissivity drops on passing through the connectivity threshold (50 per cent occupancy), as one would expect. However, quite counter-intuitively, near the onset of diffraction, resonant phenomena induce a complete reversal in the sense of this transmissivity switch, i.e. the transmission is seen to increase as the metal occupancy is increased.DstlEngineering and Physical Sciences Research Council (EPSRC

Resonantly overcoming metal opacity

Copyright © 2013 American Institute of PhysicsThe near-perfect response of electrons in metals to low-frequency electromagnetic fields makes even a sub-skin-depth film almost completely opaque to microwave radiation. Here, it is experimentally demonstrated that by surrounding a ∼60 nm aluminium film with an array of thin resonant cavities, over 35% of the microwave radiation incident can be transmitted over a discrete set of narrow bands. This represents an enhancement of ∼1000 times over an isolated film and allows for a frequency selective screen with a thickness less than 1/70th of the operating wavelength that may be tuned through choice of resonant geometr

Toroidal circular dichroism

We demonstrate that the induced toroidal dipole, represented by currents flowing on the surface of a torus, makes a distinct and indispensable contribution to circular dichroism. We show that toroidal circular dichroism supplements the well-known mechanism involving electric dipole and magnetic dipole transitions. We illustrate this with rigorous analysis of the experimentally measured, polarization-sensitive transmission spectra of an artificial metamaterial, constructed from elements of toroidal symmetry. We argue that toroidal circular dichroism shall be found in large biomolecules with elements of toroidal symmetry and should be taken into account in the interpretation of circular dichroism spectra of organics

Independently controlling permittivity and diamagnetism in broadband, low-loss, isotropic metamaterials at microwave frequencies

Copyright © 2015 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters, Volume 106 (10), article 101908, and may be found at http://dx.doi.org/10.1063/1.4915097A metamaterial based on the design of Shin et al. [Phys. Rev. Lett. 102, 093903 (2009)] that allows independent control of its permeability and permittivity has been fabricated and experimentally characterised. It is comprised of an array of metallic cubic-shaped elements with faces that are connected only through six orthogonal spokes emanating from the centre. The permeability is tailored through appropriate patterning of the faces, thereby controlling the propagation of eddy currents around the cubic elements while permittivity may be controlled by the thickness and dielectric constant of the inter-cube spacers.Engineering and Physical Sciences Research Council (EPSRC)DST

New enantiomeric phenomena in toroidal media

Optical activity is a phenomenon ubiquitous across natural and artificial structures and is generally understood in terms of the coupling between electric and magnetic dipoles [1]. Usually, this dipole approximation is sufficient to explain optical activity in most media. In metamaterials however, engineering of the structure allows for designs where a conventional multipole (electric and magnetic dipole) response is suppressed in favour of more exotic excitations typically excluded from the standard multipole expansion. Here, we report on the first computational study of optical activity in a metamaterial that cannot be attributed to conventional multipoles, and can only be accounted for by the inclusion of the toroidal dipole