Optical Torque from Enhanced Scattering by Multipolar Plasmonic Resonance

TL;DR

This paper demonstrates that multipolar plasmon resonance can significantly enhance scattering-induced optical torque on nanoparticles, surpassing absorption effects and enabling advanced nanoscale optical manipulation.

Contribution

It reveals that resonant scattering, driven by multipolar plasmon modes, can dominate optical torque generation, a novel insight for plasmonics and nanomanipulation.

Findings

Scattering can contribute up to 80% of total optical torque.

Multipolar modes convert angular momentum in non-circular particles.

Scattering-dominant torque is highly mode-specific.

Abstract

We present a theoretical study of the optical angular momentum transfer from a circularly polarized plane wave to thin metal nanoparticles of different rotational symmetries. While absorption has been regarded as the predominant mechanism of torque generation on the nanoscale, we demonstrate numerically how the contribution from scattering can be enhanced by using multipolar plasmon resonance. The multipolar modes in non-circular particles can convert the angular momentum carried by the scattered field, thereby producing scattering-dominant optical torque, while a circularly symmetric particle cannot. Our results show that the optical torque induced by resonant scattering can contribute to 80% of the total optical torque in gold particles. This scattering-dominant torque generation is extremely mode-specific, and deserves to be distinguished from the absorption-dominant mechanism. Our findings might have applications in optical manipulation on the nanoscale as well as new designs in plasmonics and metamaterials.