Unidirectional reflectionless propagation in a non-ideal parity-time metasurface based on far field coupling

Gu, Xin; Bai, Ruiping; Zhang, Cong; Jin, Xing Ri; Zhang, Ying Qiao; Zhang, Shou; Lee, Young Pak

doi:10.1364/oe.25.011778

Cited by 50 publications

(28 citation statements)

References 57 publications

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“…2(b)) of the metasurface prove the totally suppressed and highly efficient retro-reflection (4% from left port and 90% from right port at 11.8 GHz), which provides a new perspective for designing an asymmetric optical system for wave manipulation. Unidirectional reflectionless propagation has also been achieved in a non-Hermitian metasurface consisting of two silver ring resonators coupled in the far field [33]. This metasurface shows a bilateral unidirectional reflectionless propagation that is insensitive to the incident angle (∼ 25 • ) and independent of polarizations.…”

Section: Unidirectional Propagationmentioning

confidence: 96%

“…A two-port metasurface can be described by a scattering matrix (Fig. 1(b)) that can be obtained by transmission matrix [33], impedance matrix [34], or admittance matrix [35], and sometimes combine with the coupled mode equations [36]. In metasurfaces satisfying PT symmetry, the scattering matrix of an active two-port system with balanced gain and loss has the form:…”

Section: Non-hermitian Metasurfacesmentioning

confidence: 99%

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Non-Hermitian Electromagnetic Metasurfaces at Exceptional Points (Invited Review)

Li¹,

Cao²,

Li³

et al. 2021

PIER

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Exceptional points are spectral singularities in non-Hermitian systems at which two or more eigenvalues and their corresponding eigenvectors simultaneously coalesce. Originating from quantum theory, exceptional points have attracted significant attention in optics and photonics because their emergence in systems with nonconservative gain and loss elements can give rise to many counterintuitive phenomena. Metasurfaces -two-dimensional artificial electromagnetic materials structured at the subwavelength scale -can provide a versatile platform for exploring such non-Hermitian phenomena through the addition of dissipation and amplification within their unit cells. These concepts enable a wide range of exotic phenomena, including unidirectional propagation, adiabatic mode conversion, and ultrasensitive measurements, which can be harnessed for technological applications. In this article, we review the recent advances in exceptional-point and non-Hermitian metasurfaces. We introduce the basic theory of exceptional point and non-Hermiticity in metasurfaces, highlight important achievements and applications, and discuss the future opportunities of non-Hermitian metasurfaces from basic science to emerging technologies.

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Section: Unidirectional Propagationmentioning

confidence: 96%

Section: Non-hermitian Metasurfacesmentioning

confidence: 99%

Non-Hermitian Electromagnetic Metasurfaces at Exceptional Points (Invited Review)

Li¹,

Cao²,

Li³

et al. 2021

PIER

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“…The multiple wave interference effect and near‐field coupling effect between layers make the few‐layer metasurface a powerful platform to tailor the reflection, transmission, and absorption of electromagnetic waves. By utilizing the multiple wave interference effect between the functional layers, Chen et al proposed a wide‐angle antireflection coating in the terahertz frequency range .…”

Section: Prominent Applications In Few‐layer Metasurfacesmentioning

confidence: 99%

Empowered Layer Effects and Prominent Properties in Few‐Layer Metasurfaces

Chen

Zhang

et al. 2019

Advanced Optical Materials

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applications have been realized based on the metamaterials, such as negative index materials, [3] invisibility cloaks, [4] and zeroindex materials. [5] Nevertheless, metamaterials are usually bulky, difficult to be fabricated, and suffer from high energy losses, which hinder their practical applications in modern photonic systems. In recent years, planar metasurfaces, the 2D equivalents of metamaterials, have attracted plenty of attentions due to their extraordinary abilities in controlling the polarization, amplitude, phase, and dispersion of electromagnetic waves. [6][7][8] Compared with bulk metamaterials, the metasurfaces have many advantages, such as ultrathin thicknesses, low losses, ease of fabrication and integration. Over the past years, single-layer metasurfaces have been widely applied in realizing polarization conversion, [9] beam deflectors, [10,11] metalenses, [12,13] holograms, [14] coding, [15] structural colors, [16,17] nonlinear metasurfaces, [18] and some other applications. Nevertheless, the interactions between lights and ultrathin single-layer metasurfaces are usually limited, resulting in low efficiency and limited controllability in some applications. [19] Moreover, the degrees of freedom for light manipulation provided by a single-layer metasurface are usually not enough in realizing multifunctional devices and some other sophisticated photonic systems.Few-layer metasurface that contains more than one functional layer provides an effective method to overcome the drawbacks of both bulk metamaterials and single-layer metasurfaces. Cheng et al. employed the concept of few-layer metasurfaces to discuss the advantages and emergent functionalities of them in ref. [20]. Few-layer metasurfaces retain the advantages of single-layer metasurfaces and can provide more degrees of freedom to manipulate electromagnetic waves. More importantly, the abundant layer effects, such as the multiple wave interference between layers and the near-field coupling effects, can enhance the interactions between lights and structures and improve the efficiency of few-layer systems. In addition, the combination of different functional layers can produce novel functions that single-layer metasurfaces can hardly realize. For example, by breaking the mirror symmetry along the propagation direction, few-layer metasurfaces can realize asymmetric transmission of linearly polarized lights. [21] By vertically integrating different metasurfaces on one substrate, optical systems with different functions can be miniaturization and integration. Recently, the few-layer metasurfaces have also been extended in the acoustic fields to realize some novel applications, such Metamaterials are 3D artificial structures proposed to surpass conventional natural materials and realize novel functions beyond traditional optical elements. Nevertheless, they are usually bulky and difficult to be fabricated. As 2D equivalents of metamaterials, metasurfaces have been proposed to overcome the drawbacks of metamaterials and fully control the polarizati...

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“…So far, unidirectional reflectionlessnesses have been proposed in some non-Hermitian Hamiltonian systems with unbalanced gain and loss [21,22,23,24,25,26,27,28,29,30,31,32], such as passive (no gain) optical waveguide [21], large optical multilayer structure [22], two-layer slab [23], plasmonic waveguide [24,25,26,27], and metamaterial [28,29,30,31,32]. In 2013, Feng et al [21] experimentally demonstrated unidirectional reflectionlessness in PT symmetry optical waveguide system, where reflection from one port was distinctly diminished.…”

Section: Introductionmentioning

confidence: 99%

“…Later, Bai et al [30] realized the unidirectional reflectionlessness based on near-field coupling of two stacked asymmetric nanostrips. Gu et al [31] and Bai et al [32] realized the polarization-insensitivity and polarization-switching unidirectional reflectionlessnesses in metamaterials based on far-field phase coupling between two resonators, respectively. However, the above studies [29,30,31,32] in metamaterials focused on single-band unidirectional reflectionlessnesses, the dual-band scheme was seldom mentioned.…”

Section: Introductionmentioning

confidence: 99%

Dual-Band Unidirectional Reflectionless Propagation in Metamaterial Based on Two Circular-Hole Resonators

et al. 2018

Self Cite

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Dual-band unidirectional reflectionless propagation at two exceptional points is investigated in metamaterial, which is composed of only two gold resonators with circular holes, by simply manipulating the angle of incident wave and distance between two resonators. Furthermore, the dual-band unidirectional reflectionless propagation can be realized in the wide ranges of incident angle from 0∘ to 50∘ and distance from 255 nm to 355 nm between two resonators. In addition, our scheme is insensitive to polarization of incident wave due to the circular-hole structure of the resonators.

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Unidirectional reflectionless propagation in a non-ideal parity-time metasurface based on far field coupling

Cited by 50 publications

References 57 publications

Non-Hermitian Electromagnetic Metasurfaces at Exceptional Points (Invited Review)

Non-Hermitian Electromagnetic Metasurfaces at Exceptional Points (Invited Review)

Empowered Layer Effects and Prominent Properties in Few‐Layer Metasurfaces

Dual-Band Unidirectional Reflectionless Propagation in Metamaterial Based on Two Circular-Hole Resonators

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