Mechanism of subwavelength imaging with bilayered magnetic metamaterials: Theory and experiment

Abstract

We present a theoretical and experimental study of a bilayered metamaterial structure for subwavelength imaging of magnetic field. The simplest version of such a structure consists of one or two linear arrays of capacitively loaded split pipe resonators. Its subwavelength physics is governed by strongly anisotropic magnetic coupling between individual resonators and by propagation of magnetoinductive waves with wavelength much shorter than the wavelength of the electromagnetic radiation in free space. It is shown that magnetoinductive waves propagating in the lateral direction are undesirable because they spread the image. Good subwavelength imaging is achieved when, due to the strong interlayer coupling, a stop band in the vicinity of the resonant frequency appears in the dispersion characteristics. The imaging properties of the single and double lens are compared and it is shown that the double lens has a superior performance. Excellent agreement is obtained between experimental and theoretical results for the magnetic field in the image plane in the operation frequency range of 30-60 MHz. It is shown that the same mechanism is responsible for image formation using bilayered planar metamaterial structures and a design of such a lens comprising two planar layers with a total of 542 elements is provided. The conclusions are not restricted to the radio frequency region because the elements can be scaled down.

Electric and magnetic excitation of coherent magnetic plasmon waves in a one-dimensional meta-chain

“…Occasionally, especially when the elements are very close, this coupling effect is not negligible and will have a substantial effect on the properties of the metamaterials. Recent studies have shown that the resonance coupling effect between split-ring resonators (SRR) can introduce magnetoinductive waves [10][11][12][13][14][15][16] In our previous theory work [27], another kind of coupling mechanism between resonance elements, …”

Thin-film magneto-inductive cables

“…Applications have been identified in magnetic field concentration [18], delay-lines [19], phase shifters [20], filters and splitters [21] and near-field lenses [22,23].…”

Hybridization effect in coupled metamaterials

“…This causes the coupling constant between resonators to become complex and leads to even more complicated dispersion [62]. Up to now, a series of microwave devices based on MI waves have been proposed, such as magneto-inductive waveguides [63], broadband phase shifters [64], parametric amplifiers [65], and pixel-to-pixel sub-wavelength imagers [66,67].…”