Embedded metasurfaces for robust and orientation-independent imaging applications

Abstract

Metasurfaces offer compact, lightweight alternatives to conventional optics by enabling precise wavefront control with subwavelength nanostructures. However, the mechanical fragility of pillar-based configurations limits their applicability in practical systems, particularly under routine handling and cleaning. Here, we report a mechanically robust metasurface architecture in which high refractive index nanopillars are encapsulated within a conformal SiO₂ layer. Numerical simulations indicate that the embedded design maintains stable focusing efficiency over a wide range of surrounding refractive index values of common operational media such as air, water, and oil, whereas pillar-based structures exhibit significant degradation. Experimentally, the embedded design preserves diffraction-limited focusing and high-contrast imaging performance. After standard mechanical cleaning, the embedded metasurface maintains over 90% of its initial focusing efficiency, while unprotected metasurfaces exhibit an efficiency reduction of approximately 88%. The near-symmetric dielectric layer enhances orientation-independent optical response, demonstrating identical imaging performance under forward and reverse illumination. A magnification ratio of 1.29 is observed between two configurations. This ratio arises from the difference in object distances, which is caused by the thickness differences in the substrate and the encapsulated SiO₂ layer. This CMOS-compatible, bidirectional, and mechanically stable metasurface platform provides a scalable approach to integrated flat optics for advanced imaging and sensing applications.

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Identifiers

ORCID for Kian Shen Kiang: orcid.org/0000-0002-7326-909X

ORCID for Bruce (Jun-Yu) Ou: orcid.org/0000-0001-8028-6130

ORCID for Jize Yan: orcid.org/0000-0002-2886-2847

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