Experiments of Negative-Index Refraction in Optical Frequency Region

Recently, significant attention has been devoted to a new class of smart materials – so-called negative-index materials (NIM). There are some direct experimental demonstrations of NIM in the microwave frequency region, but not in optical frequency region. Here we report a kind of optical negative-index material which is 2D photonic crystal and, by measuring the refractive angle of the transmitted beam through a prism fabricated from this material, we determine the effective n. These experiments directly confirm this material is an optical negative-index one.