V.A. Fedotov

Sharp Trapped-Mode Resonances in Planar Metamaterials with a Broken Structural Symmetry

We report that a resonance response with a very high quality factor can be achieved in a planar metamaterial by introducing symmetry breaking in the shape of its structural elements, which enables excitation of trapped modes, i.e., modes that are weakly coupled to free space.

Metamaterial Analog of Electromagnetically Induced Transparency

We demonstrate a classical analog of electromagnetically induced transparency in a planar metamaterial. We show that pulses propagating through such metamaterials experience considerable delay. The thickness of the structure along the direction of wave propagation is much smaller than the wavelength, which allows successive stacking of multiple metamaterial slabs leading to increased transmission and bandwidth.

Metamaterial with negative index due to chirality

Artificial magnetism, negative permeability and negative refractive index are demonstrated in 3D-chiral metamaterial that shows giant polarization rotation and circular dichroism. ∗ As presented at the Quantum Electronics and Laser Sciences Conference (CLEO/QELS 2008), San Jose, CA, USA, 5 May 2008, paper QMA4.

Giant Gyrotropy due to Electromagnetic-Field Coupling in a Bilayered Chiral Structure

We report the first experimental evidence that electromagnetic coupling between physically separated planar metal patterns located in parallel planes provides for exceptionally strong polarization rotatory power if one pattern is twisted in respect to the other, creating a 3D chiral object. In terms of optical rotary power per sample of thickness equal to one wavelength, the bi-layered structure rotates five orders of magnitude stronger than a gyrotropic crystal of quartz in the visible spectrum. We also saw a signature of negative refraction for circularly polarized waves propagating through the chiral slab.

Asymmetric propagation of electromagnetic waves through a planar chiral structure

We report the first experiential observation and theoretical analysis of the new phenomenon of planar chiral circular conversion dichroism, which in some aspects resembles the Faraday effect in magnetized media, but does not require the presence of a magnetic field for its observation. It results from the interaction of an electromagnetic wave with a planar chiral structure patterned on the sub-wavelength scale, and manifests itself in asymmetric transmission of circularly polarized waves in the opposite directions through the structure and elliptically polarized eigenstates. The new effect is radically different from conventional gyrotropy of three-dimensional chiral media.

Coherent meta-materials and the lasing spaser

In 2003 Bergman and Stockman introduced the spaser, a quantum amplifier of surface plasmons by stimulated emission of radiation. They argued that, by exploiting a metal/dielectric composite medium, it should be possible to construct a nano-device, where a strong coherent field is built up in a spatial region much smaller than the wavelength. It was suggested that V-shaped metallic inclusions, combined with a collection of semiconductor quantum dots could lead to a realization of the spaser. Here we introduce a further development of the spaser concept. We show that by combining the metamaterial and spaser ideas one can create a planar narrow-diversion coherent source of electromagnetic radiation that is fuelled by plasmonic oscillations. We argue that two-dimensional arrays of a certain class of plasmonic resonators supporting high-Q current excitations belong to a new category of coherent metamaterials that provide an intriguing opportunity to create a spatially and temporally coherent laser source, the Lasing Spaser.

Giant optical gyrotropy due to electromagnetic coupling

The authors demonstrate a chiral photonic metamaterial with chirality provided by electromagnetic coupling between mutually twisted unconnected layers. In the visible and near-IR spectral ranges, the material exhibits polarization rotatory power of up to 2500°/mm and shows relatively low losses and negligible circular dichroism, making it a promising candidate for the development of chiral negative index media.

Toroidal Dipolar Response in a Metamaterial

Making a Point with Metamaterials A long-predicted electromagnetic excitation, the toroidal moment (or anapole), is associated with toroidal shape and current flow within a structure and has been implicated in nuclear and particle physics. This distinct family of electromagnetic excitations has not been observed directly because they are masked by much stronger electric and magnetic multipoles. Kaelberer et al. (p. 1510, published online 4 November) have developed a metamaterial structure based on stacked loops of inverted split-ring resonators (“metamolecules”) whose response under excitation is consistent with the existence of a toroidal moment. The metamaterial is designed so that both the electric and magnetic dipole moments induced by an incident electromagnetic wave are suppressed, while the toroidal response is isolated and resonantly enhanced to a detectable level. A material that embeds metal wire loops in a dielectric has properties consistent with an exotic electromagnetic excitation. Toroidal multipoles are fundamental electromagnetic excitations different from those associated with the familiar charge and magnetic multipoles. They have been held responsible for parity violation in nuclear and particle physics, but direct evidence of their existence in classical electrodynamics has remained elusive. We report on the observation of a resonant electromagnetic response in an artificially engineered medium, or metamaterial, that cannot be attributed to magnetic or charge multipoles and can only be explained by the existence of a toroidal dipole. Our direct experimental evidence of the toroidal response brings attention to the often ignored electromagnetic interactions involving toroidal multipoles, which could be present in naturally occurring systems, especially at the macromolecule level, where toroidal symmetry is ubiquitous.

Metamaterial with polarization and direction insensitive resonant transmission response mimicking electromagnetically induced transparency

We report on a planar metamaterial, the resonant transmission frequency of which does not depend on the polarization and angle of incidence of electromagnetic waves. The resonance results from the excitation of high-Q antisymmetric trapped current mode and shows sharp phase dispersion characteristic to Fano-type resonances of the electromagnetically induced transparency phenomenon.

Towards the lasing spaser: controlling metamaterial optical response with semiconductor quantum dots

We report the first experimental demonstration of compensating Joule losses in metallic photonic metamaterial using optically pumped PbS semiconductor quantum dots.