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The electro‐optic (EO) effect is one of the physical mechanisms enabling the dynamic response of metasurfaces, which motivates the analysis of nanoantenna arrays integrated with EO materials. It was shown earlier that chalcophosphate Sn₂P₂S₆metasurfaces can enable significant shifts of multipolar resonances by enhancing the EO response near the Curie temperature. The present work explores how the refractive index of EO materials impacts resonance shifts in metasurfaces with multipolar resonances. It is numerically demonstrated that EO nanoantennas can support pronounced multipolar resonances despite their moderate refractive index, enabling strong light confinement and substantial EO tuning, and that multipolar components of even parity exhibit the highest sensitivity to variations in the refractive index of the nanoantennas. For moderate refractive indices varying from 2.3 to 3.0, it is found that, for a given resonance, the wavelength shift resulting from a refractive index change has a relatively weak dependence on the index itself. This suggests that the refractive index plays only a marginal role in enhancing the EO shift in active photonic devices, and instead, other considerations for material selection, such as the EO coefficient magnitude, the transparency window, and ease of processing, should be of primary concern. 

High-refractive-index nanoantennas have attracted significant attention lately because of the strong excitations of electric and magnetic resonances in these nanoantennas. Here, we theoretically investigate the excitation of multipolar Mie resonances in high-refractive-index nanoantennas that are immersed in a negative-index medium. Our analysis shows a significant enhancement of magnetic resonances in this case. Furthermore, the magnetic dipolar and quadrupolar resonances exhibit a π-shift compared to these magnetic resonances in a conventional medium, which stems from the “left-handedness” of the negative-index medium. As a result, the spectral regions where electric and magnetic resonances are in-phase or out-of-phase complement, or opposite, to those in a conventional medium. Most importantly, we demonstrate nanoantenna magnetic resonances in two practical cases of negative-index media realized with common materials, such as multilayer structures with surface waves with negative effective mode index and fishnet metamaterial. These findings represent significant progress toward the realization of hybrid emitting structures that exhibit transitions with both electric and magnetic dipolar characteristics and pave the way for greater flexibility in controlling radiation patterns from quantum emitters. 

Abstract Electron‐beam deposition stands as a versatile technique utilized for the accurate and controlled thin‐film deposition of a wide range of materials that readily undergo evaporation. However, silicon, a commonly used material, is prone to oxidation during the deposition process because of the presence of water vapors and oxygen in the chamber. To overcome this challenge, a tailored approach is developed that involves controlling the deposition conditions, including the base pressure in the chamber and the deposition rate. Silicon oxidation is successfully overcome, and this results in achieving refractive index values comparable to those obtained with alternative deposition methods for amorphous silicon. The research shows that the deposition conditions can be utilized effectively to tune the refractive index, providing flexibility in achieving the desired optical properties. It is demonstrated that Mie‐resonant metasurfaces exhibit strong collective resonances, driven by the coherent coupling of Mie modes within the periodic nanoantenna lattice, as evidenced by distinct spectral features in the scattering response. These resonances are observed to be highly tunable, with spectral shifts corresponding to controlled variations in the electron‐beam deposition parameters and silicon oxidation. The approach enables silicon deposition for metasurfaces, which presents exciting possibilities for tailoring and designing advanced nanostructures with unique optical characteristics.