Maxwell's demon-like nonreciprocity by non-Hermitian gyrotropic metasurfaces

Letter
Open Access

Maxwell's demon-like nonreciprocity by non-Hermitian gyrotropic metasurfaces

Wenyan Wang, Wang Tat Yau, Yanxia Cui, Jin Wang, and Kin Hung Fung

Phys. Rev. Research 3, L022006 – Published 19 April 2021

Abstract

We show that Maxwell's demon-like nonreciprocity can be supported in a class of non-Hermitian gyrotropic metasurfaces in the linear regime. The proposed metasurface functions as a transmission-only Maxwell's demon operating at a pair of photon energies. Based on multiple scattering theory, we construct a dual-dipole model to explain the underlying mechanism that leads to the antisymmetric nonreciprocal transmission. The results may inspire new designs of compact nonreciprocal devices for photonics.

Received 5 October 2020
Accepted 26 March 2021

DOI:https://doi.org/10.1103/PhysRevResearch.3.L022006

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Geometrical & wave optics Light propagation, transmission & absorption Magneto-optical effect Magnons Photonic crystals

Atomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Wenyan Wang^1,2, Wang Tat Yau ², Yanxia Cui¹, Jin Wang ^3,*, and Kin Hung Fung ^2,†

¹College of Physics and Optoelectronics, Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China
²Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China
³School of Physics, Southeast University, Nanjing 211189, China

^*jinwang@seu.edu.cn
^†khfung@polyu.edu.hk

Article Text

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Issue

Vol. 3, Iss. 2 — April - June 2021

Subject Areas

Metamaterials

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Images

Figure 1
Schematic diagram of antisymmetric Maxwell's demon-like operation supported by a metasurface composed of dimer unit cells. The metasurface (a) forbids the penetration of photons with frequency $f_{1}$ in downward incidence, while it (b) allows the penetration of photons with frequency $f_{1}$ in upward incidence. The same metasurface also (c) allows the penetration of photons with frequency $f_{2}$ in downward incidence, while it (d) forbids the penetration of photons with frequency $f_{2}$ in upward incidence.
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Figure 2
(a) Schematic diagram of the metasurface consisting of gyromagnetic (blue) and isotropic dielectric (gray) cylinders. (b) Top view of the unit cell of the periodic system in (a). Periodic conditions are applied on the $x$ axis throughout all calculations. Plane waves illuminating from $- y$ and $+ y$ directions are denoted as downward incidence by a red arrow and upward incidence by a blue arrow, respectively. (c) The numerical and analytical transmittance spectra, represented as solid lines and open circles, respectively, under downward (panel at top) and upward (panel at bottom) incidences. The transmittance spectra of a lossless system in both directions are shown as black dashed lines. The insets show the $E_{z}$ field patterns of those cylinders at those transmittance extrema. (d) The transient electric field $E_{z}$ at $f_{1}$ and $f_{2}$ . The marked arrows indicate the direction of the incident waves. Material parameters are $ε_{m} = 15$ , $H_{0} = 500$ Oe, and $M_{s} = 1750 / (4 π)$ G, and $n_{d} = 10 + 2.8 i$ . Geometrical parameters are $Λ = 50$ mm, $r = 1$ mm, and $a = 12$ mm.
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Figure 3
Comparison of analytical transmittance (T) spectra (solid lines with open circles), analytical absorption (A) spectra (solid lines with half-filled circles) from Eq. (4), and the magnitude of the scattered field of the dielectric cylinder ( $| s_{0}^{d} |$ ) (green solid lines) under (a) downward incidence and (b) upward incidence, denoted by the superscripts $-$ and +, respectively. The local extrema of the three spectra under two incidences are simultaneously located at $f_{1}$ and $f_{2}$ , marked by the black dashed lines.
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Figure 4
The effects of $k$ , the imaginary part of the dielectric constant, on (a) numerical transmission difference $Δ T$ and (b) numerical absorption difference $Δ A$ . The white circles and black spheres in (a) and (b) represent the peak and depth locations of difference of A in Eq. (4), respectively. (c) The vertical cross section of (b) at $f_{1}$ and $f_{2}$ , showing the effect of $k$ on $Δ A$ at those frequencies. Excellent agreements are obtained between the closed form (CF) in Eq. (4) and numerical results.
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Figure 5
(a) Schematic diagram of mode hybridization of a gyromagnetic (blue) and dielectric (gray) cylinder array. The collective resonance modes of an isolated gyromagnetic cylinder array (MD, denoted as a blue arrow) and an isolated dielectric cylinder array (ED, denoted as a gray arrow) are hybridized into absorptive dominant modes $g^{A}$ ( $| ϱ^{Y} | \leq | ϱ^{d} |$ ) and transmissive dominant modes $g^{T}$ ( $| ϱ^{Y} | > | ϱ^{d} |$ ) by merging the two arrays. (b) The magnitude of the component corresponding to the dielectric cylinder $| ϱ^{d} |$ in two eigenvectors, $g_{1}$ (green line) and $g_{2}$ (orange dashed line). The crossing point of the two lines is found at $f_{0} = 3.80$ GHz. (c) The magnitude of the excitation coefficient, $| η_{1, 2}^{\pm} |$ , to the two eigenvectors, $g_{1}$ and $g_{2}$ , under upward (or downward) wave excitation. The subscripts 1, 2 of $| η |$ refer to the excitation of the eigenmodes with corresponding indices. The superscripts $-$ and + denote the downward and upward incidences, respectively.
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