Demonstration of Near-Infrared Negative-Index Materials
  Metal-based negative refractive index materials have been extensively studied in the microwave region. However, negative-index metamaterials have not been realized at near-IR or visible fre-quencies due to difficulties of fabrication and to the generally poorer optical properties of metals at these wavelengths. In this paper, we report the first fabrication and experimental verification of a transversely structured metal-dielectric-metal multilayer exhibiting a negative refractive in-dex around 2 mm. Both the amplitude and the phase of the transmission and reflection were measured experimentally, and are in good agreement with a rigorous coupled wave analysis. 
Shuang Zhang, Wenjun Fan, N. C. Panoiu, K. J. Malloy, R. M. Osgood and   S. R. J. Brueck