Templated Dewetting of Optical Glasses—A Novel Fabrication Approach of All-Dielectric Metasurfaces

Metasurfaces require the integration of materials with accurate control over position, size and shape for high optical efficiency. This is commonly achieved using well-established lithographic or chemical<i> </i>processes. Nevertheless, such processes suffer from intrinsic limitations over throughput or flexibility, and hence remain difficult to scale up and adapt to large area, flexible or stretchable substrates. Here, we present a novel fabrication approach based on controlled templated fluid instabilities of thin optical glasses, to self-organize a variety of large index contrast all-dielectric metasurfaces. Given the right annealing time-temperature settings, initial film thickness and underlying pattern, the breakup of the film can occur at prescribed locations resulting in nano-objects of tunable position, shapes and sizes. Such control paves the way towards simple fabrication route of advanced 2D and quasi-3D photonic architectures (Das Gupta, Sorin et. al. <i>Nature Nanotechnology</i>, 14 (4), 320 (2019); Martin-Monier, Sorin et. al. <i>Physical Review Applied</i> 3, 034025 (2021)). Low processing temperatures enable large-scale use of rigid but also unconventional flexible and stretchable substrates. Such structures enable strong electromagnetic field confinement, and are shown to have varieties of applications in sensing, light management and second harmonic generation. In particular, by dewetting successively increasingly thick layers, inter-particle gap down to 10 nm could be achieved. By critically coupling the in-plane diffractive mode with the radiative dipolar mode in such structures, sharp Fano-type resonances are demonstrated in the near visible region. These resonances are exploited to monitor protein monolayer concentrations down to 0.5mg/ml (Das Gupta, Sorin et. al. <i>Nature Nanotechnology</i>, 14 (4), 320 (2019)). Tailoring the underlying texture, we will also discuss recent results of chalcogenide based architectures exhibiting high second harmonic conversion efficiency of 10^-6 in the UV region (Das Gupta, Sorin et. al., <i>Nanophotonics</i> 10, 3465 (2021)). Finally, we will further highlight the flexibility of our approach by presenting recent results on highly reflecting all-dielectric nanostructures, as well as tailored architectures for improved index sensing.