Quasi-dark resonances with antiferromagnetic order in silicon metasurfaces

Quasi-dark resonances exhibiting antiferromagnetic order are theoretically investigated in a near-infrared metasurface composed of square slotted rings etched in a thin silicon layer on glass substrate. Access to the quasi-dark mode is achieved by reducing the symmetry of the metasurface according to the findings of a detailed group theory analysis. A thorough finite-element study reveals the key optical properties of the antiferromagnetic order quasi-dark mode, namely resonant wavelengths, quality factors, angular dispersion, and its robustness against optical extinction losses. It is demonstrated that the thickness of the silicon metasurface can adjust the asymmetry degree of the resonant Fano lineshape without affecting substantially its quality factor. Furthermore, tuning of the resonant wavelength can be achieved without significant modification of the Fano lineshape by controlling the angle of incidence of the impinging planewave. Overall, the work presents an all-dielectric, near-infrared metasurface for the excitation of sharp resonances with antiferromagnetic order, which can find use in emerging applications based on this particular configuration of artificial optical magnetism and/or strong field confinement and light-matter interaction.This work was supported by the CNR-FAPESP biennial (2022–2023) bilateral project StReAM “Strongly Resonant All-dielectric Metasurfaces based on quasi-dark and toroidal modes”. V.D. and H.E.H.F. thank the Brazilian Agency National Council of Technological and Scientifc Development (CNPq) for the fnancial support. H.E.H.F. was also funded by the São Paulo State Science Foundation (FAPESP), under the Project No 2015/24517-8, and by the Coordination for the Improvement of Higher Education Personal (CAPES)-PRINT/Institutional Internationalization Program, under Process No 88887.574915/2020-00. J.F.A. received funding from Ministerio de Ciencia, Innovación y Universidades of Spain under Juan de la Cierva-Incorporación grant and he also acknowledges the support of the projects PID2019-107270RB-C21 and PID2019-109072RB-C31 funded by MCIN/AEI/10.13039/501100011033 and FEDER “A way to make Europe”, PDC2021-121172-C21 funded by MCIN/AEI/10.13039/501100011033 and the European Union “Next generation EU”/PTR, and project S2018/ NMT-4326 funded by the Comunidad de Madrid and FEDER Program