Multi-functional metasurfaces based on direct nano-imprint of Titania sol gels coatings

Dielectric Mie resonators are taking momentum in the last years thanks to their peculiar properties in light management at visible and near-infrared frequencies. However, their full exploitation demands for cheap materials and versatile fabrication methods, extendible over large surfaces and potentially C-MOS compatible. Here, a sol-gel deposition and nano-imprint lithography method is used to obtain Titania-based Mie resonators over large areas (several mm 2), showing that this platform can potentially be exploited for light management with different devices. First, it is demonstrated their use for structural colours and efficient band pass filters covering the visible spectrum. Then, exploiting sharp Fano resonances in reflection, their potential for refractive index sensing is addressed obtaining a figure of merit of ~20. Finally, when placing the resonators on porous silica, a large and reversible colour tuning can be produced as a result of water adsorption within the substrate porosity. These results open the path to Titania sub-micrometric structures for applications as a multi-functional metamaterial for smart windows, displays and all-optical sensing.