Structure-induced broadband tunable resonances in soft material based dielectric metasurfaces

Abstract

The dielectric metasurfaces using soft materials have generated opportunities in metamaterials by manipulating light interaction at a sub-wavelength scale. Here, we study the low-index dielectric metasurface consisting of a monolayer of dielectric micro-spheres in the visible region. The metasurface exhibits optical resonances, which appear as dips in the reflectivity spectra measured using the state-of-the-art micro-reflectivity facility. The origin of resonances is due to the diffraction of light on the corrugated surface, which appears as a grating mode or due to the light trapped within the micro-spheres termed as the leaky mode. The tunability of resonant modes is discussed as a function of the lattice constant and the effective refractive index of the metasurface. The experimental results are validated using the finite-difference time-domain simulations and theoretical calculations. The impact of the substrate refractive index is studied which shows higher refractive index contrast between the sample and the substrate, more light is confined within the metasurface. The proposed soft material-based metasurfaces can be used as a mask for making more complex photonic structures, generating structural coloration, and material base for rapid sensing.