Liquid crystal clad near-infrared metamaterials with tunable negative-zero-positive refractive indices

Near-infrared metamaterials that possess a reconfigurable index of refraction from negative through zero to positive values are presented. Reconfigurability is achieved by cladding thin layers of liquid crystal both as a superstrate and a substrate on an established negative-index metamaterial, and adjusting the permittivity of the liquid crystal. Numerical results show that the index of refraction for the proposed structure can be changed over the range from ?1 to +1.8 by tuning the liquid crystal permittivity from 2 to 6 at a wavelength of 1.4 ?m.