Low loss multilayer frequency selective surface NIMs for the Mid-IR: Modeling, synthesis and characterization

Over the last few years there has been increasing interest in metamaterials research because of the exciting applications made possible by refractive index engineering. Negative index materials (NIMs) were first theorized in 1968 by Veselago [1], who predicted that a material possessing simultaneously negative permittivity ε and permeability μ would exhibit novel properties, including backward-propagating waves, near-field focusing, and a modified Snell's law. Pendry's more recent recognition that a flat slab of material with n = -1 could be used as a "perfect lens" [2], started a drive to experimentally demonstrate NIMs from the RF regime through optical wavelengths [3]. However, many NIM experiments have suffered from high absorption and impedance mismatch losses, and most optical NIMs have been very thin with respect to the wavelength, reducing their utility in practical devices. We have previously reported our use of a flexible architecture based on periodic arrays of sub-wavelength metallo-dielectric structures coupled with genetic algorithm (GA) optimization [4] to minimize the losses inherent in NIMs [5]. We have also investigated optimizing larger metallo-dielectric stacks in order to realize practical, volumetric NIMs [6]. In this paper, we describe our progress in modeling the response of two-layer metallo-dielectric NIMs as well as designing, fabricating and characterizing two-layer metallo-dielectric NIMs for the mid-IR.