Directional Light Scattering of a Single Si Nanoparticle Revealed by Three-Dimensional Near-Field Optical Microscopy

Manipulation of light propagation is indispensable for the development of photonic circuits and nano-optical devices. In this study, we investigated the optical properties of Mie resonances in a single Si nanoparticle via dark field and near-field optical microscopy. The dark field spectrum of the nanoparticle exhibits electric and magnetic dipolar modes in the visible to near-infrared spectral region. The near-field spectrum shows red-shifted and enhanced peaks due to these resonances. From the electromagnetic simulation, we revealed that these unique near-field characteristics originate from the constructive interaction of the incident and scattered fields. We also performed three-dimensional near-field microscopy and demonstrated that the magnetic dipolar mode results in wider spatial extension and directional forward scattering than does the electric dipolar mode does. These findings indicate that the interaction of the magnetic dipolar mode with near-field light is desirable for controlling light propagation in various applications.