Keywords:Mie resonance, Metamaterial, Nanophotonics
Meta-atoms that support magnetic and electric dipoles at visible frequencies are key building-blocks for optical metamaterials. Recently, liquid-type metamaterials in which meta-atoms are dispersed are proposed as metafluids. In contrast to solid-state metamaterials, the liquid metamaterials can be applied to solution-phase spectroscopy and optofluidic devices to enhance signals and/or offer advanced functionalities. As a component of liquid metamaterials, a plasmonic meta-atom composed of silica core decorated with metal nanoparticles have been studied so far; however, the magnitude of the magnetic dipole (MD) is weaker than that of the electric dipole (ED) on the plasmonic meta-atom. Here we propose silicon nanospheres as a novel meta-atom that can be dispersed in solution such as water and alcohol. The silicon nanospheres exhibit strong resonant scattering by Mie-type ED and MD resonances. We show that the silicon nanosphere colloid can control effective refractive index in a wide range and are an excellent candidate for metafluids because of advantages such as low-loss, simple symmetric structure, and strong optical magnetism.