A.V. Rogacheva

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.

Mirror that does not change the phase of reflected waves

We report that electromagnetic wave reflected from a flat metallic mirror superimposed with a planar wavy metallic structure with subwavelength features that resemble “fish scales” reflects like a conventional mirror without diffraction, but shows no phase change with respect to the incident wave. Such unusual behavior resembles a reflection from a hypothetical zero refractive index material, or “magnetic wall”. We also discovered that the structure acts as a local field concentrator and a resonant “amplifier” of losses in the underlying dielectric.

Optical magnetic mirror

We report demonstration of an optical magnetic mirror achieved by nanostructuring a metal surface. In contrast to normal mirrors, it inflicts only small change to the phase of a reflected wave, offering intriguing applications.

Non-radiating excitations, vector potential waves and toroidal metamaterials

A long chase for the elusive dynamic toroidal moments has been recently concluded by detecting a spectral signature of the toroidal dipolar resonance in the response of a specially designed electromagnetic metamaterial [1]. This observation brings up a new interest to the prediction made by Afanasiev and Stepanovsky in 1994 that a combination of oscillating toroidal and conventional electric dipoles forms a non-trivial non-radiating electromagnetic system producing gauge-irreducible waves of vector potential in absence of electric and magnetic fields [2]. Here we report the observation of extremely narrow transmission resonances in toroidal void metamaterials that result from the interference of its electric and toroidal dipolar response thus indicating the existence of such non-radiating system. Our results provide new evidence for the discussion on independent physical significance of vector-potential and its role as an independent information carrier.

Magnetic Mirror on Optical Frequency

We report demonstration of an optical magnetic mirror achieved by nanostructuring a metal surface. In contrast to normal mirrors, it inflicts only small change to the phase of a reflected wave, offering intriguing applications.