Modified fishnet structure with a wide negative refractive index band and a high figure of merit at microwave frequencies

Abstract

Since realization of negative refractive index (NRI) metamaterials in 2001, which is about 20 years after its introduction as a pure academic concept in 1968, there has been much curiosity and enthusiasm for this field of study. Despite numerous potential applications, different loss mechanisms inherent to such materials have severely restricted their widespread usage. Based on this, NRI metamaterials with low losses are extensively studied in the literature. In this paper, we present a design to realize NRI at microwave frequencies which, to some degree, overcomes the limitations imposed by high intrinsic losses pertinent to such category of materials via bestowing a figure of merit (FOM) as high as 139.3. The layout includes two opposing parts, each containing a square slab in the middle of two crossing wires. The theoretical discussions unveiling the physics behind the NRI behavior, as well as effects of geometrical parameters, temperature, and the use of different metals on the FOM, are extensively discussed.