Nonlinearity-induced nanoparticle circumgyration at sub-diffraction scale

Lei-Ming Zhou,Shali Shi,Yaqiang Qin,Yunfeng Jin,Yuanjie Yang,Lu Huang,Liantuan Xiao,Cheng-Wei Qiu,Hao Shi,Yuqiang Jiang,Honglian Guo

doi:10.1038/s41467-021-24100-0

Abstract

The ability of light beams to rotate nano-objects has important applications in optical micromachines and biotechnology. However, due to the diffraction limit, it is challenging to rotate nanoparticles at subwavelength scale. Here, we propose a method to obtain controlled fast orbital rotation (i.e., circumgyration) at deep subwavelength scale, based on the nonlinear optical effect rather than sub-diffraction focusing. We experimentally demonstrate rotation of metallic nanoparticles with orbital radius of 71 nm, to our knowledge, the smallest orbital radius obtained by optical trapping thus far. The circumgyration frequency of particles in water can be more than 1 kHz. In addition, we use a femtosecond pulsed Gaussian beam rather than vortex beams in the experiment. Our study provides paradigms for nanoparticle manipulation beyond the diffraction limit, which will not only push toward possible applications in optically driven nanomachines, but also spur more fascinating research in nano-rheology, micro-fluid mechanics and biological applications at the nanoscale.

Highlights

The ability of light beams to rotate nano-objects has important applications in optical micromachines and biotechnology
The gold nanoparticles (GNPs) were trapped in distilled water and illuminated by a continuous laser beam with green light, and could be observed by the scattered light or photoluminescence
The rotations with such high frequency and subwavelength dimensional orbital radius achieved in our experiments are very suggestive of micromachines or applications in nano-rheology

Summary

Introduction

The ability of light beams to rotate nano-objects has important applications in optical micromachines and biotechnology. Unlike previous light-driven orbital rotations, such as those based on high-order Laguerre-Gaussian beams, we create this highspeed orbital rotation at subwavelength scale by merely utilizing a circularly polarized femtosecond Gaussian laser beam with a nonlinear particle. Detailed investigation of this system revealed that the nonlinearity of the particle material results in the rotation orbital, and increases the conversion efficiency of photonic SAM to particle’s OAM, mediated by the surface plasmon resonance excited in the moving metallic particle

Methods

Results

Conclusion