Optofluidic Control of Colours with Metasurfaces

We demonstrate theoretically and experimentally dynamic tuning of optical response of dielectric metasurfaces based on the high-sensitivity of surface lattice resonances to their surrounding environment. This tuneability is achieved by controlling a dielectric permittivity contrast between the substrate and the superstrate, which leads to two different tuning mechanisms: a spectral shift or an on/off switching of surface lattice resonances. Experimentally, we demonstrate this tuning using an optofluidic platform combining a silicon metasurface on a glass substrate and a variable water level to control the refractive index of the superstrate and show a dynamic change of the optical response of the metasurface, manifested through change of its colouring. This concept may be applied for various applications, including high-resolution dynamic displays, sensing and anticounterfeiting protection.