Anomalous Transparency in Photonic Crystals and its Dependence on the Refractive Index Difference

Abstract

We have recently reported on the ability of photonic crystals (PhCs) to be isotropic and transparent in a region above the first band gap where the wavelength of light starts to be comparable with the feature sizes of the PhC [1]. Such behavior was previously observed below the first band gap region mainly for PhCs with a period and feature sizes that are much smaller than the wavelength of light. We therefore referred to this phenomenon as ‘anomalous transparency’ in photonic crystals. This finding indicates that one could design PhCs for applications in the visible range such as optical cloaking and gradient index-based metamaterials, which would have much larger feature sizes and hence would be easier to fabricate and allow a relaxed manufacturing tolerance. In this report we study the influence of the refractive index contrast in the PhC on the anomalous transparency in view of understanding within which refractive index range the phenomenon could be exploited.