Circular Huygens Dipoles: Unidirectional Spin-Angular Momentum from Achiral Nanoparticles

TL;DR

This paper introduces the Circular Huygens Dipole concept, demonstrating how a single silicon nanocuboid can control light's directionality and spin at the nanoscale, enabling reconfigurable spin-optics and sensing applications.

Contribution

The paper presents the first realization of Circular Huygens Dipoles in a single silicon nanostructure, enabling deterministic control of light's polarization and directionality.

Findings

Achieved unidirectional spin-angular momentum control in silicon nanocuboids.

Demonstrated polarization switching between right- and left-circular states.

Enabled a passive, reconfigurable spin-to-linear polarization conversion.

Abstract

Simultaneous control over the directionality and spin of light at the nanoscale is a central goal in nanophotonics with applications ranging from quantum information to advanced biosensing. We introduce the concept of the Circular Huygens Dipole and numerically demonstrate its realization in a single Si nanocuboid. We show that the polarization of an incident linear wave controls the interference between co-located circular electric and magnetic dipoles excited in phase quadrature. This enables deterministic switching of the forward-scattered radiation between purely right- and left-circularly polarized states. The system also functions as a directional spin-to-linear polarization converter. Our findings establish a robust, passive method for reconfigurable spin-directional control in a simple, monolithic silicon nanostructure, opening avenues for chip-scale spin-optics, chiral quantum interfaces, and novel sensing platforms.