Abstract
.Core-shell building blocks have been found useful in recent years as inclusions, in the search for metamaterials with tailored properties. Either the core or the shell of these composite inclusions may be metallic, and the dielectric component may be both radially anisotropic and radially inhomogeneous. In tunable anisotropic metamaterials, the tuning may then be achieved through the host, the core, or some combination thereof. However a theoretical picture is harder to build. Here we propose an approach to an effective medium theory for such materials, valid in the quasi-static limit. The method proceeds first by homogenising the interior of complex particle, and then uses standard anisotropic effective medium methods to provide bulk effective homogenized parameters. By varying the degree of inhomogeneity in the core, shell and dielectric-metal material volume fractions, the technique can be used as a tool for the design of metamaterials with specifically engineered properties. We find that metamaterial properties can be readily tuned by reorienting the optical axis of the host (e.g., liquid crystal). In particular, there is a possibility of switching between hyperbolic and conventional anisotropic metamaterial properties by changing inclusion shell properties.
Highlights
Over recent years it has been increasingly the case that natural materials do not possess properties sufficiently versatile to satisfy modern demanding engineering requirements
The challenge involved in calculating bulk properties of complex metamaterials is significant, when, as in the cases considered in this paper, the host materials are anisotropic
We show the results of representative calculations, which show the key physical effect to which we wish to draw attention, in figs. 15 and 16
Summary
Over recent years it has been increasingly the case that natural materials do not possess properties sufficiently versatile to satisfy modern demanding engineering requirements. By comparison with usual articulations of these theories, the problem that we discuss contains extra complexity This complexity is a result firstly of the need to include correctly size-dependent core parameters, secondly of the inhomogeneity of the particulate inclusions, and thirdly of the optical anisotropy associated with some or all of the components of the composite. A principal advantage of our work is that the input formulae are analytic, and relatively trivial numerical methods are required in order to apply the results to systems of interest other than those which we use in our examples The focus of these calculations is on metamaterial properties, but we note possible applications in biosensors based on surface plasmonic resonance [44, 45]. 3 to derive results for effective dielectric properties of structured core-shell particles embedded in a host medium. In refs. [59, 60] it has been labelled “internal isotropic core-shell mean particle isotropic core-shell mean particle
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