Self-assembled glass-based Fano resonant metasurfaces

Dielectric metasurfaces require the integration of large index contrast materials with accurate control over position and size for high optical efficiency. Their fabrication usually relies on well-established lithographic techniques. While lithography bears considerable advantages in terms of reproducibility and accuracy, it remains a time and cost intensive process that remains restricted in terms of materials, and difficult to scale up to large-area and non-rigid substrates. Chalcogenide glasses constitute a class of materials particularly suited for metasurfaces, thanks to their low intrinsic losses coupled with their tunable high refractive indices. The challenges associated with the nanostructuring of glassy materials has however limited their use in nanophotonics. Here, we rely on the glass characteristic viscous properties and destabilizing Van der Waals interactions, to show the rearrangement of thin chalcogenide films into well-ordered and defect free structures at the nanoscale. In particular, we show the fabrication of arrays of a variety of chalcogenides nano-objects, both continuous and isolated, with a variety of sizes and structures, and on different, rigid, flexible and stretchable substrates. Such controlled large area arrays are shown to have strong field enhancement leading to Fano resonances, which finds applications as biosensor and second harmonic generation.