Researchers are actively involved in the exploitation of electro-optic and nonlinear effects that produce zero-index and negative-index materials. By embedding aligned nematic liquid crystals with coated dielectric nanospheres, researchers at Pennsylvania State University (University Park, PA) have demonstrated the possibility of creating a new type of metamaterial with a refractive index that is tunable from negative, through zero, to positive values.
The material properties of this new metamaterial are predicted using Maxwell Garnet mixing-rule equations for a medium with three regions: the host liquid crystal, the nanosphere outer shell, and the nanosphere core. Though these materials are nonmagnetic with relative permeability equal to 1, the combination of the permittivities at the appropriate resonances in conjunction with the electric- or magnetic-field-induced permittivity change in the liquid-crystal host material enables the refractive-index tunability over a wide dynamic range from the visible to the microwave region. Contact Iam Choon Khoo at [email protected].