Enhanced Mie resonance in a low refractive index colloidal metamaterial aided by nematic liquid crystal

We report studies on a colloidal metamaterial system in which sub-micron-sized (~530 nm) dielectric particles (SiO2) are dispersed in a nematic liquid crystal. Despite the low refractive index (~1.45) of the particles, Mie resonances are enhanced in the system due to the anisotropic nature of the host medium, as evident from the UV–Vis extinction spectra. The resultant improvement in light confinement and the interference between the dipolar Mie resonant modes give rise to forward directional scattering. Further, the Dark Field Hyperspectral Imaging and Heterodyne Near Field Scattering experiments demonstrate that the forward scattering intensity can be tuned by switching the refractive index of the liquid crystal medium between its anisotropic limits achieved by the application of an ac electric field. The extinction spectra with the deconvoluted resonance modes calculated using Mie theory and the Finite Elements Method (FEM) analysis support the experimental findings. The FEM calculations also reveal the formation of photonic nanojet from the particle. The enhanced Mie resonance and tunable forward scattering in the low index SiO2 particles induced by the nematic liquid crystal medium are highly promising for bio-compatible nano-photonic applications.