Perfect diffraction metagratings supporting bound states in the continuum and exceptional points

Resonance coupling in non-Hermitian systems can lead to exotic features, such as bound states in the continuum (BICs) and exceptional points (EPs), which have been widely employed to control the propagation and scattering of light. Yet, similar tools to control diffraction and engineering spatial wa...

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Bibliographic Details
Published inarXiv.org
Main Authors Zi-Lan Deng, Feng-Jun, Li, Li, Huanan, Li, Xiangping, Alù, Andrea
Format Paper Journal Article
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 22.09.2021
Subjects
Coupling
Diffraction efficiency
Insulators
Physics - Optics
Selectivity
Wave fronts
Waveguides
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Summary:Resonance coupling in non-Hermitian systems can lead to exotic features, such as bound states in the continuum (BICs) and exceptional points (EPs), which have been widely employed to control the propagation and scattering of light. Yet, similar tools to control diffraction and engineering spatial wavefronts have remained elusive. Here, we show that, by operating a suitably tailored metagrating around a BIC and EPs, it is possible to achieve an extreme degree of control over coupling to different diffraction orders in metasurfaces. We stack subwavelength metallic slit arrays on a metal-insulator-metal waveguide, enabling a careful control of the coupling between localized and guided modes. By periodically tuning the coupling strength from weak to strong, we largely tailor the overall spectrum and enable the emergence of singular features, like BICs and EPs. Perfect unitary diffraction efficiency with large spectrum selectivity is achieved around these singular features, with promising applications for arbitrary wavefront shaping combined with filtering and sensing.
ISSN:2331-8422
DOI:10.48550/arxiv.2109.10533