Photonic Metamaterials

We review some of our recent results on photonic metamaterials operating at optical frequencies. In a series of interferometric pulse propagation experiments on negative index metamaterials, we have demonstrated simultaneous negative phase and group velocity of light at 1.5 mum wavelength. By optimizing the structure parameters and utilizing silver instead of gold, the losses of the negative index metamaterial have been reduced significantly. Further downscaling of the lattice constant has brought the negative refractive index to the red end of the visible spectrum. We have also fabricated negative index metamaterials with up to three functional layers. Besides of unusual dispersion properties, metamaterials can also exhibit very interesting polarization effects. We have performed experiments and numerical calculations for a chiral planar metamaterial design. This design comprises dense arrays of double-layer gammadions. The excitation of anti-symmetric current oscillations in the two layers leads to pronounced circular dichroism.