We present a coupler-free, multi-mode refractive index sensor based on nanostructured split ring resonators (SRRs). The fabricated SRR structures exhibit multiple reflectance peaks, whose spectral positions are sensitive to local dielectric environment and can be quantitatively described by our standing-wave plasmonic resonance model, providing a design rule for this multi-mode refractive-index (MMRI) sensor. We further manifest that the lower-order modes possess greater sensitivity associated with stronger localized electromagnetic field leading to shorter detection lengths within five hundreds nanometers, while the higher-order modes present mediate sensitivity with micron-scale detection lengths to allow intracellular bio-events detection. These unique merits enable the SRR-based sensor a multi-functional biosensor and a potential label-free imaging device.
Based on Maxwell's equations and Mie theory, strong sub-wavelength artificial magnetic and electric dipole resonances can be excited within dielectric resonators, and their resonant frequencies can be tailored simply by scaling the size of the dielectric resonators. Therefore, in this work we hybridize commercially available zirconia and alumina structures to harvest their individual artificial magnetic and electric response simultaneously, presenting a negative refractive index medium (NRIM). Comparing with the conventional NRIM constructed by metallic structures, the demonstrated all-dielectric NRIM possesses low-loss and high-symmetry advantages, thus benefiting practical applications in communication components, perfect lenses, invisible cloaking and other novel electromagnetic devices.
We employ dielectric metamaterials to construct an all-dielectric negative refractive waveguide (NRW) in which the negative Goos–Hänchen effect is used to trap the incident wave in simulation. The use of a dielectric metamaterial eliminates the ohmic losses from metal, which not only lengthens photon-trapping time but also enables the NRW to maintain the ability to slow light. In addition, we validate numerical simulation with experimental measurements, which agree with the simulation results with a frequency offset of <1.2%. Finally, by verifying that light is slowed in an all-dielectric NRW, we claim that a dielectric metamaterial can possess negative identities.
Abstract:The major issue regarding magnetic response in nature-"negative values for the permeability μ of material parameters, especially in terahertz or optical region" makes the electromagnetic properties of natural materials asymmetric. Recently, research in metamaterials has grown in significance because these artificial materials can demonstrate special and, indeed, extraordinary electromagnetic phenomena such as the inverse of Snell's law and novel applications. A critical topic in metamaterials is the artificial negative magnetic response, which can be designed in the higher frequency regime (from microwave to optical range). Artificial magnetism illustrates new physics and new applications, which have been demonstrated over the past few years. In this review, we present recent developments in research on artificial magnetic metamaterials including split-ring resonator structures, sandwich structures, and high permittivity-based dielectric composites. Engineering applications such as invisibility cloaking, negative refractive index medium, and slowing light fall into this category. We also discuss the possibility that metamaterials can be suitable for realizing new and exotic electromagnetic properties.
OPEN ACCESSSymmetry 2011, 3 284
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