Tunable phase-gradient-based optical tweezers

TL;DR

This paper introduces a novel type of optical tweezers that utilize phase gradient manipulation to create tunable potential wells, enabling flexible and easy control of nanoparticle trapping and manipulation.

Contribution

It presents a new method for designing holograms to generate phase-gradient-based optical tweezers with tunable trapping potentials.

Findings

Able to trap nanoparticles in custom-shaped optical spots

Demonstrated shifting and positioning of nanoparticles using optical gears

Offers flexible design and straightforward control of optical traps

Abstract

Conventional optical tweezers are generated by the intensity gradient of highly focused laser beams, but the requirement of strong intensity gradient limits the tunability of optical traps. Here we show a new type of optical tweezers with tunable potential wells by manipulating the phase gradient of light. Using a new method to calculate holograms, we can design desirable phase profiles and intensity distributions of optical patterns. Optical force arising from the phase gradient creates tunable potential wells for versatile optical manipulation, such as trapping nanoparticles in peanut-shaped optical spots, and positioning and shifting nanoparticles in optical gears as demonstrated in our experiments. The phase-gradient-based optical tweezers have several merits including flexible design and easy control, which open a new way for optical trapping and manipulation.