A.S. Schwanecke

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.

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.

Nanostructured Metal Film with Asymmetric Optical Transmission

We demonstrate for the first time a nanostructured planar photonic metamaterial transmitting light differently in forward and backward directions.

Broken time reversal of light interaction with planar chiral nanostructures.

We report unambiguous experimental evidence of broken time-reversal symmetry for the interaction of light with an artificial nonmagnetic material. Polarized color images of planar chiral gold-on-silicon nanostructures consisting of arrays of gammadions show intriguing and unusual symmetry: structures, which are geometrically mirror images, lose their mirror symmetry in polarized light. The symmetry of images can be described only in terms of antisymmetry (black-and-white symmetry) appropriate to a time-odd process. The effect results from a transverse chiral nonlocal electromagnetic response of the structure and has some striking resemblance with the expected features of light scattering on anyon matter.

Polarization conversion and “focusing” of light propagating through a small chiral hole in a metallic screen

Propagation of light through a thin flat metallic screen containing a hole of twisted shape is sensitive to whether the incident wave is left or right circularly polarized. The transmitted light accrues a component with handedness opposite to the incident wave. The efficiency of polarization conversion depends on the mutual direction of the hole’s twist and the incident light’s wave polarization handedness and peaks at a wavelength close to the hole overall size. We also observed a strong transmitted field concentration at the center of the chiral hole when the handedness of the chiral hole and the wave’s polarization state are the same.

Enhanced microwave transmission through quasicrystal hole arrays

The authors report on the observation of enhanced microwave transmission through quasiperiodic hole arrays in metal films. The fraction of transmitted light reaches 50% in a self-standing metal film and approaches 90% when the film is sandwiched between thin dielectric slabs, while the holes occupy only 10% of the sample area. The maximum transmission exhibits a Breit-Wigner resonance behavior, accompanied by zero phase change and rendering the film almost invisible over a wide frequency range. The extraordinary transmission phenomenon is interpreted in terms of resonances in the self-consistent interaction between holes, which are represented by effective electric and magnetic dipoles.

Extraordinary properties of light transmission through a small chiral hole in a metallic screen

The true three-dimensional finite element numerical solution of Maxwells equations shows that the propagation of light through a thin flat free-standing metallic screen containing a hole of twisted shape is sensitive to whether the incident wave is left or right circularly polarized. The intensity map and polarization state of light are dramatically changed depending on the mutual direction of the holes twist and the incident lights wave polarization handedness. We also observed a strong concentration of the transmitted field at the centre of the chiral hole when light in the object plane rotates against the twist of the investigated gammadion type structure.

Gallium/aluminum nanocomposite material for nonlinear optics and nonlinear plasmonics

We report on a new type of composite metallic structure for nonlinear optics and nonlinear plasmonics, created by grain boundary penetration of gallium into an aluminum film. These composite films form mirrorlike interfaces with silica and show an exceptionally broadband phase-transition-based nonlinear response to optical excitation.

Nano metamaterials and photonic gratings by nanoimprint and hot embossing

This paper reviews our recent progress in nanoimprint lithography and hot embossing for the fabrications of planar photonic meta-materials and photonic gratings. With these technologies, dielectric, metallic chiral structures and dense gratings in sizes from sub micrometres down to sub-100 nm were successfully fabricated. Characterisations of these meta-materials and photonic structures indicate these materials and structures are functional. It can be concluded that nanoimporint lithography and hot embossing are capable of achieving large area planar optic meta-materials and photonic structures such as dense gratings. This progress suggests the great prospect of these techniques for fast speed patterning of important meta materials and photonic nanostructures with high throughput at low cost in mass production in the future.

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.