Enabling self-induced back-action trapping of gold nanoparticles in metamaterial plasmonic tweezers

TL;DR

This paper demonstrates the use of metamaterial plasmonic tweezers leveraging the self-induced back-action effect to achieve stable trapping of 20 nm gold nanoparticles with low laser power, enhanced by Fano resonance.

Contribution

It introduces the application of SIBA effect in metamaterial tweezers and explores its synergy with Fano resonance for improved nanoparticle trapping.

Findings

Stable trapping of 20 nm gold particles achieved.

Trap stiffness up to 4.18 fN/(nm*mW/$de$^2$) at low power.

Existence of tunable hotspots for particle sorting.

Abstract

The pursuit for efficient nanoparticle trapping with low powers has led to optical tweezers technology moving from the conventional free-space configuration to advanced plasmonic tweezers systems. However, trapping nanoparticles smaller than 10 nm still remains a challenge even for plasmonic tweezers. Proper nanocavity design and excitation has given rise to the self-induced back-action (SIBA) effect offering enhanced trapping stiffness with decreased laser power. In this work, we investigate the SIBA effect in metamaterial tweezers and its synergy with the exhibited Fano resonance. We demonstrate stable trapping of 20 nm gold particles for on-resonant and off-resonant conditions with experimental trap stiffnesses as high as 4.18 fN/(nm*mW/$\mu$m$^2$ and very low excitation intensity of about 1 mW/$\mu$m$^2$. Simulations reveal the existence of two different groups of hotspots per unit cell of the metamaterial array. The two hotspots exhibit tunable trap stiffnesses and this is a unique feature of these systems. It can allow for sorting of particles and biological molecules based on their size, shape, and refractive index.