Polarization-dependent bandwidth in low-index plasmonic metamaterials.

We investigate the visible range, less-than-one index bandwidth, n(λ)<1, of an optical metamaterial structure composed of plasmonic gold nanoparticles, and show that it is highly dependent on the polarization of incident light. The full-wave finite element method is used to obtain the spectral characteristics of the structure. We have found spectral bands over which the structure shows the desired low index. Further, a possible increase of the bandwidth by as much as 270% is demonstrated by a change in the incident polarization that extends the low-index bandwidth range (503-600 nm) asymmetrically into a wider range (485-750 nm) covering longer wavelengths close to near infrared. This asymmetric overlap might have the potential for new optical applications.