Fano resonance-assisted all-dielectric array for enhanced near-field optical trapping of nanoparticles

TL;DR

This paper demonstrates how Fano resonance in an all-dielectric nanostructure significantly enhances near-field optical trapping of nanoparticles, achieving high trap stiffness and enabling multi-particle trapping.

Contribution

It introduces a novel all-dielectric quadrupole nanostructure exploiting Fano resonance to greatly improve trap stiffness and enable multi-particle trapping, surpassing previous dielectric approaches.

Findings

Twenty-fold enhancement of trap stiffness at resonance.

High trap stiffness of 1.19 fN/nm for 100 nm particles.

Simultaneous trapping of two particles at different locations.

Abstract

Near-field optics can overcome the diffraction limit by creating strong optical gradients to enable the trapping of nanoparticles. However, it remains challenging to achieve efficient stable trapping without heating and thermal effects. Dielectric structures have been used to address this issue, but they usually offer weak trap stiffness. In this work, we exploit the Fano resonance effect in an all-dielectric quadrupole nanostructure to realize a twenty-fold enhancement of trap stiffness, compared to the off-resonance case. This enables a high effective trap stiffness of $1.19$ fN/nm for 100 nm diameter polystyrene nanoparticles with 3.5 mW/$\mu$m$^{2}$ illumination. Furthermore, we demonstrate the capability of the structure to simultaneously trap two particles at distinct locations within the nanostructure array.