Diffraction-limited axial double foci and optical traps generated by optimization-free planar lens

Long Ma,Peng Jin,Chen Chen,Jian Guan,Jianlong Zhang,Jiubin Tan,Yiqun Wang,Jie Lin

doi:10.1515/nanoph-2019-0482

Abstract

Abstract Axial diffraction-limited multiple foci are a kind of investigated focal field for trapping multiple nano-particles. We first experimentally generated diffraction-limited axial double foci by optimization-free binary planar lens and theoretically demonstrated it, which can be applied in multi-particle trapping. The proposed binary planar lens was analytically designed. The BPL has a numerical aperture of 0.9 and a focal length of 150 μm. The focal field of the binary planar lens, which is composed of diffraction-limited axial double foci, was first experimentally validated. The measured maximum lateral full widths at half maximum of the two generated focal spots were diffraction-limited and consistent with the theoretical. The axial double foci formed two stable optical traps that can trap two Rayleigh dielectric particles simultaneously. The radial, azimuthal and axial optical forces of the double optical traps are in good uniformity, which are 0.98, 0.99 and 0.96, respectively.

Highlights

Optical tweezers can manipulate nano-particles without physical contact, providing a significant tool in many scientific fields, such as biology [1, 2], biophysics [3, 4], photonics [5, 6], chemistry [7,8,9,10] and measurement [11,12,13]
We first experimentally generated diffraction-limited axial double foci by optimization-free binary planar lens and theoretically demonstrated it, which can be applied in multi-particle trapping
The intensity distributions of the x, y and z polarization components are respectively same around the two foci. These results demonstrate the feasibility of the designed binary planar lens (BPL) to achieve axial double foci

Summary

Introduction

Optical tweezers can manipulate nano-particles without physical contact, providing a significant tool in many scientific fields, such as biology [1, 2], biophysics [3, 4], photonics [5, 6], chemistry [7,8,9,10] and measurement [11,12,13]. Multiple nano-particles trapping was more and more desired in the optical tweezer field [14,15,16,17]. To achieve three-dimensional d iffraction-limited multiple foci, iterative phase-retrieval algorithms have been proposed to create the modulation phase patterns [22, 24]. Amplitude or phase pupil filters were proposed to achieve axial diffraction-limited multiple foci [19, 21]. There was non-iterative pupil filter to be proposed to achieve axial diffraction-limited multiple foci [25]. To our best knowledge, there is still no experimental research on achieving axial diffraction-limited multiple foci by a single optimizationfree planar lens.

Methods

Results

Conclusion