All-Dielectric Nanophotonic via Glass Fluid Instabilities

In this thesis work, we propose to exploit an innovative micro/nano-fabrication process, based on controlled fluid instabilities of a thin viscous film of chalcogenide glass. Amorphous selenium and arsenic triselenide were used in this thesis work, and combined with functional sol-gel substrates or flexible polymeric substrates. The goal of this thesis is to show that this alternative fabrication process is well-suited for the fabrication of advanced nanophotonics devices, leveraging the high optical refractive index of chalcogenide glasses.

In a first perspective, we exploit the ability of the thin continuous film to break-up by dewetting, and â under certain given conditions that we analyzed â to rearrange itself into an ordered array of â nano-dropletsâ sitting in the depressions of a textured substrate. Such array constitutes an optical metasurface, supporting high quality-factor resonances in the visible and near-infrared. Those resonances are first leveraged to illustrate the refractive index sensing capabilities of our metasurfaces. By finely controlling the cladding structure, we demonstrate a threefold improved sensitivity (reaching a sensitivity value around 900nm/RIU). Preliminary experiments suggest that our metasurface can be used as an efficient label-free biosensor. In a second perspective, the exact nature of those dielectric (Mie-type) resonances is elucidated and exploited to fabricate low-bandwidth reflection filters. A 1D filter, based on the dewetting on a thin encapsulated film into periodic array of nanowires, as well as a 2D filter, are fabricated and optically characterized. The resonant reflection is analytically modelled for the 1D filter. The 2D filter exhibits up to 97% reflection and operates over a large range of incident angles. A complex resonant state, characteristic of an anapole, is observed experimentally, highlighting the rich light-matter interactions with this type of surface, and paving the way for advanced photonics applications. In a third perspective, we propose to rely on discontinuous dewetting to selectively fill high aspect-ratio nanocavities. We exploit this fabrication method to realize monochromatic metalens operating in the visible. The constraining metalens design is faithfully reproduced on the silicon mold and on the intermediate working stamp, but the cavities filling on the polymeric replica is incomplete, thus offering only a few percent in focusing efficiency. Suggestions to overcome this problem are proposed. The serendipitous observation of anisotropic and ordered dewetting-front patterns is also thoroughly discussed.

In conclusion, this thesis work highlights the strength of templated dewetting (an inherently low-cost, facile and scalable process), and justifies by way of examples its relevance for the fabrication of nanophotonics devices.