Photonic metamaterials have driven the development of innovative devices with novel functionalities. Research in this field has relied upon noble plasmonic metals that suffer from optical loss, low-melting-points, cost and incompatibility with CMOS technology. Alternative material platforms such as chalcogenide semiconductors, oxides, and nitrides have been explored to overcome these challenges. Refractory metal oxides are highly versatile and are often overlooked in the realization of metamaterials and metadevices. Metal-oxide bilayers grown by vapor deposition, followed by annealing, enable a class of metamaterial coatings (meta-coatings) that offer tuneable resonant behaviour across visible frequencies. These meta-coatings are fabricated without nanopatterning allowing for large-scale fabrication.
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