Directional light scattering by germanium trimer and its metasurface structures under the substrate effects

Abstract

Considering germanium (Ge) material with one of the highest refractive index and semi-metal properties, the light scattering properties of Ge trimer and its metasurface structures are studied theoretically in this paper. In contrast to other dielectric materials, for which the magnetic-type resonance is commonly dominant, Ge has a strong electric-type resonance due to its semi-metal properties, which can be seen in the visible and near-infrared spectral range. The influence of the unique feature on the Fano line shapes can be reflected in the scattering spectra. Simultaneously, taking into account the substrate effects, we show that the behavior of the light scattering anisotropy exhibits a big difference in the presence of the different substrates, which can be manipulated to some extent. The results can provide a feasible way to control the “hot spots” in the local light field. Our work in this paper shows that Ge trimers as an excellent candidate can be applied to enhanced spectroscopy, directional sources, and other nanometer photonic devices, as well as on metasurface structures.