Controllable Optical Resonances and Unidirectional Scattering by Core-shell Nanoparticles

TL;DR

This paper explores how core-shell nanoparticles can be engineered to support tunable electric and magnetic resonances, enabling controlled optical scattering directions for advanced nanophotonic applications.

Contribution

It systematically analyzes mode evolution in core-shell nanoparticles and demonstrates tunable unidirectional scattering through geometric engineering.

Findings

Mode transition occurs at a core-shell ratio of 0.5.

Electric and magnetic resonances can be engineered for desired scattering.

Unidirectional scattering is tunable via geometric parameters.

Abstract

Nanoparticles supporting a distinct series of Mie resonances have enabled a new class of nanoantennas and provide efficient ways to manipulate light at the nanoscale. The ability to flexibly tune the optical resonances and scattering directionality are particularly essential for various applications ranging from biosensing to nanolasers. In this paper, we investigate the core-shell nanoparticles that support both electric and magnetic Mie resonances and for the first time systematically reveal the mode evolution from a pure high-index dielectric nanosphere to a pure plasmonic one, where it has a sudden transition when core-shell ratio increases from 0.4 to 0.5. Furthermore, by engineering the electric and magnetic resonances, we demonstrate the unidirectional forward and backward scattering in such a system and reveal its tunability via geometric tuning.