Theoretical and experimental research on designer surface plasmons in a metamaterial with double sets of circular holes.

The designer surface plasmons (DSPs) are studied by the use of a kind of metamaterial with a structure of double sets of circular holes: subwavelength apertures, and indentations. The diameter and spacing of the indentations are smaller at least one order of magnitude than those of the apertures. A theoretical model is built to analyze the DSPs sustained by the indentations by using effective dipoles method. The influence of the DSPs on the transmission property is revealed for electromagnetic waves passing through the apertures. In order to verify the theoretical predication, a set of the metamaterial samples is made and the transmission spectra are measured in microwave regime. Our results provide a new proof for the existence of DSPs and are promising for proposing some techniques for optoelectronic devices in terahertz and microwave regime.

Broadband gradient index microwave quasi-optical elements based on non-resonant metamaterials.

Utilizing non-resonant metamaterial elements, we demonstrate that complex gradient index optics can be constructed exhibiting low material losses and large frequency bandwidth. Although the range of structures is limited to those having only electric response, with an electric permittivity always equal to or greater than unity, there are still numerous metamaterial design possibilities enabled by leveraging the non-resonant elements. For example, a gradient, impedance matching layer can be added that drastically reduces the return loss of the optical elements due to reflection. In microwave experiments, we demonstrate the broadband design concepts with a gradient index lens and a beam-steering element, both of which are confirmed to operate over the entire X-band (roughly 8-12 GHz) frequency spectrum.

An efficient broadband metamaterial wave retarder.

Metamaterials with anisotropic electromagnetic properties have the capability to manipulate the polarization states of electromagnetic waves. We describe a method to design a broadband, low-loss wave retarder with graded constitutive parameter distributions based on non-resonant metamaterial elements. A structured metamaterial half-wave retarder that converts one linear polarization to its cross polarization is designed and its performance is characterized experimentally.

Hybrid resonant phenomena in a SRR/YIG metamaterial structure.

We consider the hybridization of the resonance of a SRR metamaterial with the gyromagnetic material resonance of yittrium iron garnet (YIG) inclusions. The combination of an artificial structural resonance and natural material resonance generates a unique hybrid resonance that can be harnessed to make tunable metamaterials and further extend the range of achievable electromagnetic materials. A predictive analytic model is applied that accurately describes the characteristics of this SRR/YIG hybridization. We suggest that this hybridization has been observed in experimental data presented by Kang et al. [Opt. Express, 16, 8825 (2008)] and present numerical simulations to support this assertion. In addition, we investigate a design for optimizing the SRR/YIG structure that shows strong hybridization with a minimum amount of YIG material.