Dual focused coherent beams for three-dimensional optical trapping and continuous rotation of metallic nanostructures.

Xiaohao Xu,Chang Cheng,Yao Zhang,Hongxiang Lei,Baojun Li

doi:10.1038/srep29449

Abstract

Metallic nanoparticles and nanowires are extremely important for nanoscience and nanotechnology. Techniques to optically trap and rotate metallic nanostructures can enable their potential applications. However, because of the destabilizing effects of optical radiation pressure, the optical trapping of large metallic particles in three dimensions is challenging. Additionally, the photothermal issues associated with optical rotation of metallic nanowires have far prevented their practical applications. Here, we utilize dual focused coherent beams to realize three-dimensional (3D) optical trapping of large silver particles. Continuous rotation of silver nanowires with frequencies measured in several hertz is also demonstrated based on interference-induced optical vortices with very low local light intensity. The experiments are interpreted by numerical simulations and calculations.

Highlights

Of vapor bubbles[3,27]
In this work, we utilize dual focused coherent beams as optical tweezers to trap and manipulate metallic nanostructures in water. 3D optical trapping of large metallic particles is realized using a silver nanoparticle with a diameter as large as 800 nm, which noticeably expands size of metallic particles trapped previously by conventional optical tweezers
(d) Interference pattern generated using the two coherent beams output from FP1 and FP2. (e) Energy spectrum and scanning electron microscope (SEM) image of the synthesized silver nanostructures. (f) SEM images of the silver nanostructures used in the experiment

Summary

Introduction

Of vapor bubbles[3,27]. the continuous optical rotation of metallic nanowires with low light intensity remains challenging. When the two beams are tuned to be coherent, axial trapping stability can be considerably enhanced due to the sharp gradient field generated by interference, as theoretically predicted by previous works[29,30]. Inspired by these findings, in this work, we utilize dual focused coherent beams as optical tweezers to trap and manipulate metallic nanostructures in water. A y-polarized laser beam (wavelength λ = 1550 nm) is split using a 1 × 2 fiber optical coupler (1:1 splitting ratio) and launched into fiber probes FP1 and FP2 (see Supplementary Fig. S1 for microscopic images).

Results

Discussion

Conclusion