We report the realization of a coherent perfect absorber, using pair passive resonators coupled to microwave transmission line in background, which can completely absorb light its parity-time (PT-)symmetric phase but not broken phase. Instead balancing material gain and loss, we exploit incident waves open system as an effective so that ideal PT symmetry be established by only materials. Such route will construct PT-symmetric metamaterials also tunable optical elements general. It provides...

This paper reports on the experimental observation of topologically protected edge state and exceptional point in an open Non-Hermitian system. While theoretical underpinning is generic to wave physics, simulations experiments are performed for acoustic system whose structure has non-trivial topological properties that can be characterized by Chern number provided a synthetic dimension introduced. Unidirectional reectionless propagation, hallmark point, unambiguously observed both experiments.

In optics, the two main mechanisms for enhancing Goos-H\"anchen (GH) shift of a reflected light beam have common shortcoming: The maximum is located exactly at reflectance dip, which makes hard to detect. Here authors tune excitation guided modes in compound grating-waveguide structure, realize quasibound states continuum (quasi-BICs) with ultrahigh $Q$-factors. Assisted by these quasi-BICs, GH peak can be greatly enhanced. This giant high used $e.g.$ ultrasensitive sensors,...

In this paper, we elucidate the formation of bound states in continuum (BICs) compound grating waveguide structures from perspective momentum mismatch. As complex lattice reduces to a simple lattice, excitable guided resonance turns into an unexcitable BIC due Herein, refer state as mismatch driven BIC. Interestingly, incidence changes normal oblique, single splits dual BICs nonzero tangential incident light. Distinct conventional symmetry-protected and accidental BICs, lie sections photonic...

Graphene has shown intriguing optical properties as a new class of plasmonic material in the terahertz regime. In particular, modes graphene nanostructures can be confined to spatial size that is hundreds times smaller than their corresponding wavelengths vacuum. Here, we show numerically by designing such deep-subwavelength scales, one obtain with desired radiative and dark modes. By placing vicinity each other, further demonstrate electromagnetically induced transparency (EIT), analogous...

New structures with richer electromagnetic properties are in high demand for developing novel microwave and optic devices aimed at realizing fast light-based information transfer processing. Here we show theoretically that a topological photonic state exists hexagonal LC circuit short-range textures the inductance, which is induced by band inversion between p- d-like modes carrying orbital angular momentum, realize this experimentally planar microstrip arrays. Measuring both amplitude phase...

Based on the selective excitations of forward and backward propagating resonant guided modes, we achieve $dual$ bound states in continuum ($dual$ BICs) a compound grating waveguide structure composed four-part periodic layer layer. Assisted by quasi-BIC corresponding to mode (quasi-BIC 1) one 2), large $positive$ $negative$ GH shifts can be simultaneously realized. Also, contrast shift enhanced conventional transmission-type resonance, positive negative assisted dual quasi-BICs possess 100%...

Without using intrinsic chiral metamaterials with complex structures, here we use achiral metasurfaces to realize giant extrinsic chirality empowered by quasi-bound states in the continuum (quasi-BICs). The proposed metasurface is mainly attributed breaking of mirror symmetry whole system, combining incident waves. transmittance two different polarization and signs circular dichroism (CD) can be arbitrarily controlled tilting plane relative incoming Remarkably, simultaneously select at bands...

Optical resonators with high quality ( Q ) factors are paramount for the enhancement of light–matter interactions in engineered photonic structures, but their performance always suffers from scattering loss caused by fabrication imperfections. Merging bound states continuum (BICs) provide us a nontrivial physical mechanism to overcome this challenge, as they can significantly improve quasi-BICs. However, most reported merging BICs found at Γ point (the center Brillouin zone), which...

Abstract For many modern photonics applications, significant nonlinear optical interactions are crucial. However, achieving this typically demands powerful laser sources and extended interaction area because most natural materials exhibit extremely weak nonlinearities. Hence, integrating optics into novel nanophotonics devices poses a challenge. In work, an asymmetrical metasurface is proposed that combines effective zero‐index media with bound states in the continuum (BIC). This scheme...

Abstract The polarization of electromagnetic waves is a fundamental property that influences their propagation direction and state, represents critical physical parameter in modern applications such as signal transmission, target recognition, precision measurement. Conventional control devices based on metamaterials are often sensitive to structural perturbations, presenting challenges for practical applications. In contrast, topologically protected photonic have demonstrated photon...

This paper presents the high-gain low-profile subwavelength substrate-integrated Fabry-Pérot (FP) cavity antennas with artificial magnetic conductor (AMC) sheets. A partially reflective planar AMC sheet and a ground plane are used as two reflectors of FP-type resonant for an ultra-thin design. The is fully filled dielectric substrate further reduction thickness antenna easy integration. microstrip patch embedded into feed. As design examples, designed to operate at 10 GHz fixed overall λ...

A noteworthy challenge in actual wireless sensors is the intrinsic sensing resolution and sensitivity associated with response to external perturbation be measured. To address issue, we report realization of enhanced a passive system, consisting three coupled resonators. The input wave exploited as an effective gain our open thus ideal parity-time (PT) symmetry can established, rather than balancing real loss. Then third-order exceptional points are obtained ternary PT symmetric systems....

The topological characteristics, including invariant orders, band inversion, and the edge mode (TEM) in photonic insulators, have been widely studied. Whether people can take advantage of intriguing modes simple one-dimensional systems to implement some practical applications is an issue which are increasingly concerned about. In this work, based on a dimer chain composed ultra-subwavelength resonators, we verify experimentally that TEM effective second-order parity-time (PT) system immune...

Although toroidal dipole (TD) resonance is a highly localized mode with high quality (Q) factor, in most chiral structures the TD much weaker than electric or magnetic resonances and contributes little to response. In this Letter, we theoretically propose all-dielectric metasurface that possesses giant optical chirality certain degree of incident-angle robustness induced by strong resonance. Interestingly, symmetry system can be broken simultaneously at oblique incidence produce quasi-bound...

Bound states in the continuum (BICs) artificial photonic structures have received considerable attention since they offer unique methods for extreme field localization and enhancement of light-matter interactions. Usually, symmetry-protected BICs are located at high symmetric points, while positions accidental achieved by tuning parameters will appear some points momentum space. Up to now, accurately design position BIC space is still a challenge. Here, we theoretically experimentally...

The sandwich metamaterial based on "honeycomb-like" porous carbon combined ferroferric oxide (Fe3O4) was reported in this paper. By manipulation of the content and Fe3O4 for adjusting complex permittivity permeability, as-prepared composite P–C-800@Fe3O4 unit cells were used to optimize electromagnetic metamaterials broadband absorption. For normal incidence waves, demonstrated an excellent absorption frequency range 5–18 GHz achieved high at low frequency. Meanwhile, structure also can...

Optical Tamm states, a kind of interface modes, are also called plasmon-polaritons. They experimentally observed in photonic heterostructures based on microstrip transmission lines. The position optical states can be designed exactly under effective impedance match and phase shift conditions. Our results show that the band gaps have effect negative-permittivity or negative-permeability media constructing modes. simulations experimental agree with each other quite well.

We propose a scheme for subwavelength electromagnetic diode by employing the nonreciprocal electromagnetically induced transparency (EIT) in metamaterials. One-way response, with 17.36 dB transmission contrast and −4.4 dBm operating power, is conceptually demonstrated microwave waveguide system asymmetric absorption varactor as nonlinear medium inclusion. Such low-threshold high-contrast action comes from EIT mechanism, which possesses narrower sharper features than Lorentz resonance. This...