Michael S. Rill

Gold Helix Photonic Metamaterial as Broadband Circular Polarizer

Corkscrew Polarizer Strong optical activity, measured in terms of a materials ability to polarize light, usually requires a material several hundred wavelengths thick. Gansel et al. (p. 1513, published online 20 August; see the cover) show that the tunable electromagnetic response of metamaterials may offer a route to reduce the amount of material required for strongly optically active materials. Based on the standard metamaterials design of the splitring resonator, photolithography was used to define an array of three-dimensional gold nanocorkscrews. Just a single wavelength thickness of the corkscrew design was required for a circular polarizer operating over an octave of bandwidth. A three-dimensional array of gold nano-helices can polarize light over a wide range of wavelengths. We investigated propagation of light through a uniaxial photonic metamaterial composed of three-dimensional gold helices arranged on a two-dimensional square lattice. These nanostructures are fabricated via an approach based on direct laser writing into a positive-tone photoresist followed by electrochemical deposition of gold. For propagation of light along the helix axis, the structure blocks the circular polarization with the same handedness as the helices, whereas it transmits the other, for a frequency range exceeding one octave. The structure is scalable to other frequency ranges and can be used as a compact broadband circular polarizer.

Photonic metamaterials by direct laser writing and silver chemical vapour deposition

We fabricate planar magnetic photonic metamaterials via direct laser writing and silver chemical vapor deposition, an approach, which is also suitable for three-dimensional structures. Retrieval of the effective metamaterial parameters reveals the importance of bi-anisotropy.

Bianisotropic Photonic Metamaterials

In metamaterials, electric (magnetic) dipoles can be excited by the electric (magnetic) component of the incident light field. Moreover, in the description of bianisotropic metamaterials, cross terms occur, i.e., magnetic dipoles can also be excited by the electric-field component of the incident light and vice versa. For the cross terms, in the general bianisotropic case, the exciting field and dipole vectors include an arbitrary angle. For the special case of chirality, the angle is zero. In the spirit of a brief tutorial, a very simple electric-circuit description of the split-ring resonator is used to give a basic introduction to the cross terms. Mathematical details of the effective parameter retrieval are presented. Furthermore, we briefly review recent experiments on bianisotropic metamaterials operating at optical frequencies.

Negative-index bianisotropic photonic metamaterial fabricated by direct laser writing and silver shadow evaporation

We present the blueprint for a novel negative-index metamaterial. This structure is fabricated via three-dimensional two-photon direct laser writing and silver shadow evaporation. The comparison of measured linear optical spectra with theory shows good agreement and reveals a negative real part of the refractive index at around 3.85 microm wavelength -- despite the fact that the metamaterial structure is bianisotropic owing to the lack of inversion symmetry along its surface normal.

Photonic metamaterials by direct laser writing and silver chemical vapor deposition

We fabricate planar magnetic photonic metamaterials via direct laser writing and silver chemical vapor deposition, an approach, which is also suitable for three-dimensional structures. Retrieval of the effective metamaterial parameters reveals the importance of bi-anisotropy.

Photonic metamaterials by direct laser writing

We present a planar magnetic metamaterial fabricated using 3D direct laser writing and silver chemical vapor deposition as well as a negative-index bi-anisotropic metamaterial metallized via silver shadow evaporation. Calculations and experiments show good agreement.