Meta-molecular devices

We report the development of a new method to both describe and design metamaterials, meta-surfaces and meta-structures in which discrete passive structures are combined into ensembles. We call these structures, meta-atoms and the structures that result are meta-molecules. By using this concept new structures can be designed with a wide range of desirable properties

3-D printed bandpass filters with coupled vertically extruded split ring resonators

The additive manufacturing process of multimaterial extrusion offers performance advantages using functional materials including conductors while making accessible the third dimension in the design of electronics. In this work we show that the additional geometrical freedom offered by this technique can be exploited for the design and realisation of filters made of three- dimensional (3D) resonators that exhibit enhanced characteristics. The coupling properties of 3D grounded square split ring resonators (SRRs) are initially explored. We demonstrate by simulations and experiments that SRRs with finite height display significantly stronger coupling compared to equivalent thin printed circuit structures. The observed trend can be exploited for designing filters with wider operational bandwidths for a given footprint, or miniaturized layouts and enhanced compatibility with fabrication limits for minimum feature size and spacing without performance degradation. This concept is demonstrated by presenting results of full-wave simulations for sample bandpass filters with identical footprint but formed by coupled 3D square SRRs of different heights, showing that filters with taller resonators exhibit increasingly wider bandwidths. Two filter prototypes with centre frequencies at 1.6 GHz and 2.45 GHz are manufactured by multimaterial 3D printing. The measured characteristics of these prototypes are found to be in good agreement with numerical simulations taking into account the effect of the lossier metallic and dielectric materials used in 3D printing and confirm the predicted larger bandwidth of the filters made of 3D SRRs with marginally higher insertion losses

Tightly coupled tripole conductor pairs as constituents for a planar 2D-isotropic negative refractive index metamaterial

A metamaterial, arranged by stacking layers of planar constituents suitably shaped to be responsive to arbitrarily linearly polarized incident waves is here shown to exhibit 2D-isotropic effective negative refractive index (NRI). The general concept underlying this metamaterial design consists of closely pairing two metallic particles to accomplish, as a result of their tight coupling, both symmetric and antisymmetric resonance modes, whose proper superposition can lead to an effective negative refraction response. The proposed structure is composed by layers of periodically arranged pairs of face coupled loaded tripoles printed on the opposite sides of a single dielectric substrate. Through a comprehensive characterization of the transmission properties of such metamaterial, together with the analysis of its dispersion diagram, conclusive evidence that the medium exhibits effective NRI properties as well as good impedance matching to free space is provided. We also describe some guidelines to design the proposed metamaterial with a prescribed operational frequency bandwidth, dependently on the structure parameters. (C) 2009 Optical Society of Americ

Tightly coupled tripole conductor pairs as constituents for a planar 2D-isotropic negative refractive index metamaterial

A metamaterial, arranged by stacking layers of planar constituents suitably shaped to be responsive to arbitrarily linearly polarized incident waves is here shown to exhibit 2D-isotropic effective negative refractive index (NRI). The general concept underlying this metamaterial design consists of closely pairing two metallic particles to accomplish, as a result of their tight coupling, both symmetric and antisymmetric resonance modes, whose proper superposition can lead to an effective negative refraction response. The proposed structure is composed by layers of periodically arranged pairs of face coupled loaded tripoles printed on the opposite sides of a single dielectric substrate. Through a comprehensive characterization of the transmission properties of such metamaterial, together with the analysis of its dispersion diagram, conclusive evidence that the medium exhibits effective NRI properties as well as good impedance matching to free space is provided. We also describe some guidelines to design the proposed metamaterial with a prescribed operational frequency bandwidth, dependently on the structure parameters. (C) 2009 Optical Society of Americ