Metal-based negative refractive index materials have been extensively studied in the microwave region. However, negative-index metamaterials have not been realized at near-IR or visible frequencies due to difficulties of fabrication and to the generally poorer optical properties of metals at these wavelengths. In this paper, we report the first fabrication and experimental verification of a transversely structured metal-dielectric-metal multilayer exhibiting a negative refractive index around 2 µm. Both the amplitude and the phase of the transmission and reflection were measured experimentally, and are in good agreement with a rigorous coupled wave analysis. PACS: 78.20.Ci; 42.25.Bs; 42.79.Dj Negative refractive-index materials are of great interest for a variety of potential applications. 1 Because natural negative refractive index materials do not exist, artificial structures have been proposed and fabricated that exhibit an effective negative index over limited frequency ranges. 2 The two principal approaches to the realization of negative refraction are metamaterials and photonic crystals. Metamaterials typically use metallic structures to provide a negative permittivity and use resonant structures (inductor-capacitor tank circuits) with a scale much smaller than the wavelength to provide a negative permeability leading to negative refraction, while § Email: brueck@chtm.unm.edu photonic crystals exhibit negative refraction as a consequence of band-folding effects. In the microwave region, negative index materials have been demonstrated using both approaches, while in the visible spectral region, negative refraction has been recently predicted. 3 In recent work, magnetically resonant structures exhibiting negative permeability have been demonstrated in the mid-infrared. 4,5 Despite theoretical studies and numerical modeling, 6,7 demonstration of negative refraction at near-infrared (near-IR) and visible wavelengths is as yet missing and, therefore, the experimental demonstration of a negative refractive index around 2 µm presented here represents an important milestone.Extension of metamaterials based on split ring resonators 8 to near-IR and visible wavelengths necessarily involves complicated and often difficult fabrication for the nanoscale metallic structures used to generate the requisite resonances. On the other hand, much of the photonic crystal literature has focused on all-dielectric structures because of their low-loss characteristics.Recent related work has used periodic metallic structures to couple incident radiation to surface plasma waves giving enhanced optical transmission through arrays of sub-wavelength holes in a metal film. 9,10 In this work, a hybrid approach is introduced which uses a pair of metal layers separated by a dielectric to provide resonant interactions (e. g. distributed inductance/capacitance) along with a periodic array of holes through the film stack to facilitate interaction with the surface plasma waves of the composite structure.The structure consists of a glass subs...
We report the synthesis of a new nanocrystal (NC) mesophase through self-assembly of water-soluble NC micelles with soluble silica. The mesophase comprises gold nanocrystals arranged within a silica matrix in a face-centered cubic lattice with cell dimensions that are adjustable through control of the nanocrystal diameter and/or the alkane chain lengths of the primary alkanethiol stabilizing ligands or the surrounding secondary surfactants. Under kinetically controlled silica polymerization conditions, evaporation drives self-assembly of NC micelles into ordered NC/silica thin-film mesophases during spin coating. The intermediate NC micelles are water soluble and of interest for biolabeling. Initial experiments on a metal-insulator-metal capacitor fabricated with an ordered three-dimensional gold nanocrystal/silica array as the "insulator" demonstrated collective Coulomb blockade behavior below 100 kelvin and established the current-voltage scaling relationship for a well-defined three-dimensional array of Coulomb islands.
We numerically demonstrate a metamaterial with both negative epsilon and negative mu over an overlapping near-infrared wavelength range resulting in a low loss negative-index material. Parametric studies optimizing this negative index are presented. This structure can be easily fabricated with standard semiconductor processing techniques.
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