Abstract
We design and construct a three-dimensional (3D) negative index medium (NIM) composed of gold hemispherical shells to supplant an integration of a split-ring resonator and a discrete plasmonic wire for both negative permeability and permittivity at THz gap. With the proposed highly symmetric gold hemispherical shells, the negative index is preserved at multiple incident angles ranging from 0° to 85° for both TE and TM waves, which is further evidenced by negative phase flows in animated field distributions and outweighs conventional fishnet structures with operating frequency shifts when varying incident angles. Finally, the fabrication of the gold hemispherical shells is facilitated via standard UV lithographic and isotropic wet etching processes and characterized by μ-FTIR. The measurement results agree the simulated ones very well.
Highlights
The advent of negative index media (NIM)[1,2] with non-existing material properties in nature has triggered a revolution in the field of electromagnetics and enabled various intriguing applications such as perfect lenses[3,4], negative Goos-Hänchen effect based slowing light systems[5,6] and perfect absorbers[7]
In this work we demonstrate a simple 3D negative index medium (NIM) composed of an array of monolithic metallic hemispherical shells, which allows both negative permeability and negative permittivity under multiple-angle incidences within the THz gap
Our proposed 3D NIM, the gold hemispherical shell is presented in Fig. 2(a), which is developed from rotating a C-shaped split-ring resonators (SRRs) denoted by a red dash arrow along the symmetry-axis 180-degree
Summary
The advent of negative index media (NIM)[1,2] with non-existing material properties in nature has triggered a revolution in the field of electromagnetics and enabled various intriguing applications such as perfect lenses[3,4], negative Goos-Hänchen effect based slowing light systems[5,6] and perfect absorbers[7]. The early demonstration of an NIM1,2 was realized via the combination of negative permeability from split-ring resonators (SRRs)[8,9] and negative permittivity from plasmonic wires[10] Such combination is experimentally infeasible at a frequency higher than the microwave region and appears sensitive to the angle and polarization of the incident excitation. There appear a few incumbent approaches to 3D NIMs, such as implementing six planar SRRs on six surfaces of a cube with orthogonally crossing continuous plasmonic wires embedded in a substrate[14] and merging multi-directional V-shaped magnetic resonators and sphere-shaped electric resonators into a monolithic structure[15] Both of the 3D NIMs confront the complexity of practical realization. Different from the antecedent 3D NIM14,15, such a metallic hemispherical shell array can be fabricated through standard UV lithographic and isotropic wet etching processes and will readily advance a variety of THz applications[16,17]
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