One-way glass for microwaves using nonreciprocal metamaterials

A. Degiron and D. R. Smith

Phys. Rev. E 89, 053203 – Published 27 May 2014

Abstract

We introduce a class of nonreciprocal metamaterials based on composite assemblies of metallic and biased ferrimagnetic elements. We show that such structures act as ultrathin one-way glasses due to the competition between two modes at the surface of the ferrimagnetic elements—a low-loss surface wave that transmits the signal on the other side of the structure and a surface spin-wave resonance that produces strong isolation levels. These findings can be adapted to existing metamaterial geometries, offering a blueprint to achieve unidirectional propagation in a variety of artificial media at radio, microwave, and millimeter wave frequencies.

Received 21 February 2014

DOI:https://doi.org/10.1103/PhysRevE.89.053203

Authors & Affiliations

A. Degiron¹ and D. R. Smith²

¹Institut d'Electronique Fondamentale, Univ. Paris-Sud and CNRS, UMR 8622, Orsay F-91405, France
²Center for Metamaterials and Integrated Plasmonics and Department of Electrical and Computer Engineering, Duke University, Box 90291, Durham, North Carolina 27708, USA

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Issue

Vol. 89, Iss. 5 — May 2014

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Images

Figure 1
(a) Dispersions of the TE-polarized surface modes supported by a 1-mm-thick ferrite slab. In red (gray curve with triangle markers), FD mode; in black, M mode; in blue (gray curve without triangles), M mode without material losses. The continuous curves are the solutions of Eqs. (2, 3, 4); the triangles are the result of FEM simulations. Also shown is the light line in air (continuous light gray line) and the lower and upper cutoff frequencies of the lossless M mode (dashed light gray lines). (b) Wavevector of the two modes in the complex plane [Same conventions as in (a)]. (c) and (d) Electric field map of the FD and M modes, respectively (for clarity, we represent the modes without material losses). Superimposed on these maps is a plot showing the $x$ component of the Poynting vector in a plane transverse to the propagation (white curves).
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Figure 2
(a) Schematic of the periodic array of ferrite particles. The blue (light gray) zone represents the computational domain flanked by periodic boundary conditions. (b) Transmission, reflection, and absorption spectra for ferrite elements with length $L = 50$ mm, respectively plotted as black, red (dark gray), and orange (light gray) lines. Insets: electric field within a unit cell at $3.4$ GHz (top) and $8.9$ GHz (bottom). (c) Same as (b) for ferrite particles with length $L = 8$ mm. (d) Power distribution (color map) and Poynting vector [blue (gray) arrows, logarithmic scale] at the center of the unit cell studied in (c) for two frequencies: $3.4$ GHz (top) and $8.9$ GHz (bottom).
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Figure 3
(a) Schematic of the nonreciprocal metamaterial. (b) Transmission spectra when the structure is illuminated from the left ( $|$ S $_{21} |^{2}$ , dashed black curve) and from the right [ $|$ S $_{12} |^{2}$ , blue (dark gray) curve]. The green (light gray) curve is the difference between the two transmission spectra. (c) and (d) Absorption and reflection spectra [same conventions as in (b)].
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Figure 4
(a) General view of the structure with a map of the instantaneous electric field evaluated at $3.45$ GHz. (b) Power distribution (color map) and Poynting vector [blue (gray) arrows, logarithmic scale] within a unit cell at $3.45$ GHz. The left and right plots correspond to an illumination from the left and right sides of the structure, respectively.
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Figure 5
(a) Transmission, (b) absorption, and (c) reflection coefficients as a function of the incident angle at $3.45$ GHz. The dashed black curves correspond to an illumination from the left side while the blue (gray) curves correspond to an illumination from the right side of the structure. (d) Electric field map for an incidence angle of $+ 40$ degrees.
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