August 1, 2014 / Vol. 39, No. 15 / OPTICS LETTERS
4587
Double-negative metamaterial from conducting spheres with a high-permittivity shell Scott Townsend,1,* Shiwei Zhou,2 and Qing Li1 1
School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006, Australia Innovative Structures Group, School of Civil, Environmental and Chemical Engineering, RMIT University, GPO Box 2476, Melbourne 3001, Australia *Corresponding author:
[email protected]
2
Received May 21, 2014; accepted June 24, 2014; posted July 1, 2014 (Doc. ID 212438); published July 31, 2014 A three-dimensional, isotropic metamaterial with double-negative behavior is proposed. The material comprises metallic spheres coated in a high-permittivity shell and dispersed in a host medium. In stark contrast to other Mie resonance-based metamaterial designs, ours relies on the metallic phase behaving as a near-perfect electric conductor, rather than a plasmonic. As such, by tuning the particle dimensions, double-negative behavior can be achieved at any frequency where one can find high-conductivity and high-permittivity materials. © 2014 Optical Society of America OCIS codes: (160.3918) Metamaterials; (260.2065) Effective medium theory; (290.4020) Mie theory. http://dx.doi.org/10.1364/OL.39.004587
Metamaterials are those composites with material properties not found in nature. Indeed, metamaterials have been produced to date with such exotic properties as negative Poisson’s ratio [1], negative thermal expansion coefficient, [2] and negative refractive index [3]. A negative refractive index material (NIM) has been of particular interest in the research community because of its proposed use in a number of exciting applications, including the invisibility cloak [4], the light trap [5], and the superlens [6]. The index is expressed as n n0 in00 and NIM implies n0 < 0. This condition can be achieved when the real part of the material permittivity and permeability are simultaneously negative, i.e., ϵ0 , μ0 < 0, and is referred to as double-negative behavior (DNG). It is worth noting that single-negative behavior [7], when n0 < 0 though only one of ϵ0 or μ0 is
