A. Papakostas

Intensity modulation and polarization rotation of visible light by dielectric planar chiral metamaterials

We have demonstrated how dielectric planar chiral surfaces can both modulate the intensity and change the polarization state of visible light diffracted from patterned surfaces. These effects are shown to be dependent on the sense of chirality of the surface and the input polarization state of the light. Individual diffracted beams can show variations of over 30% in their intensities for different input polarization states while opposite enantiomeric structures can exhibit differences of over 50%.The size of these effects could make these surfaces particularly promising candidates for the development of solid-state polarization-state detectors.

Planar chiral meta-materials for photonic devices

We report the first optical results due to the effects of two-dimensional (2D) chirality. Using electron beam lithography we have fabricated arrays of metallic planar chiral structures on dielectric substrates, with characteristic dimensions in the near infra-red, and observed the effects of their chirality on the polarization states of diffracted light. The results showed strong polarization effects, with the handedness of the individual elements having a direct effect on the sense and magnitude of rotation of the diffracted light. We believe such structures could, in the future, form the core of a new class of meta-materials with refractive indices engineered to suit individual optical applications.

Layered chiral metallic meta-materials

Using electron beam lithographic techniques we have manufactured left and right-handed forms of an artificial medium consisting of high densities of microscopic planar chiral metallic objects distributed regularly in a plane. In this artificial medium we have for the first time observed optical manifestations of planar chirality in the form of handedness-sensitive rotation of the polarization state and elliptization of visible light diffracted from the structure. Applications of such media in functional materials are discussed.

Optical properties of planar chiral meta-materials

The polarization state of visible light is found to be altered upon reflection from artificial two-dimensional chiral media. Arrays of metallic planar chiral structures were fabricated by electron beam lithography and ion beam milling. The characteristic dimensions on the chiral elements correspond to wavelengths in the near-IR. Our chiral media are found to induce strong polarization effects, with the handedness of individual elements having a direct effect on the sense and magnitude of rotation of the diffracted light.

Planar chiral meta-materials: controlling the polarization state of light in the far- and near-field

We have extended our research to the study of near-field polarization effects arising from the planar chirality. The interaction between the neighboring elements in a metallic structure can be visualized with near-field measurements. Coupling between metallic gammadions that gives rise to the scattered electromagnetic field with polarization components different from the polarization state of the incident light can be directly identified. We have also investigated far-field effects in two-dimensional gratings consisting of regular patterns of dielectric gammadions on a silicon substrate.