Active tuning of directional forward and backward scattering with metallic core/phase change shell nanoparticles

Abstract

Phase change materials, such as GeTe that exhibits reversible phase transitions between amorphous and crystalline states, are promising for reconfigurable photonic devices. Here we propose a nanoparticle composed of Au core and GeTe shell that can realize active tuning of directional scattering by adjusting the crystallinities of the GeTe shell to manipulate the electric and magnetic Mie responses of the nanoparticle. The scattering, the far-field radiation patterns and the ratio of the forward (backward) to backward (forward) scattering cross section of the hybridized nanoparticle are calculated analytically with Mie theory. The theoretical results show that when the GeTe shell is switched from amorphous phase to crystalline phase, the phase differences between the overlapped electric and magnetic modes can be changed from 0 to π. As a result, the Kerker’s first and second conditions are satisfied simultaneously, leading to tunable forward and backward scattering in near-infrared wavelength. Our results are useful for designing reconfigurable optical nanoantennas that may find applications in compact photonic circuits and all-optical wireless communications.