Enhanced optical trapping via structured scattering

TL;DR

This paper demonstrates that structured incident light fields can significantly enhance optical trapping forces on particles, achieving higher stiffness and measurement precision compared to traditional Gaussian traps.

Contribution

It introduces a novel method of structured light scattering to create stronger optical traps with phase-only modulation, surpassing conventional Gaussian traps in stiffness.

Findings

Achieved up to 27.5 times higher trap stiffness.

Demonstrated trapping of silica spheres 3.5 to 10 micrometers in size.

Enhanced measurement signal-to-noise ratio by two orders of magnitude.

Abstract

Interferometry can completely redirect light, providing the potential for strong and controllable optical forces. However, small particles do not naturally act like interferometric beamsplitters, and the optical scattering from them is not generally thought to allow efficient interference. Instead, optical trapping is typically achieved via deflection of the incident field. Here we show that a suitably structured incident field can achieve beamsplitter-like interactions with scattering particles. The resulting trap offers order-of-magnitude higher stiffness than the usual Gaussian trap in one axis, even when constrained to phase-only structuring. We demonstrate trapping of 3.5 to 10.0~$\mu$m silica spheres, achieving stiffness up to 27.5$\pm$4.1 times higher than is possible using Gaussian traps, and two orders of magnitude higher measurement signal-to-noise ratio. These results are highly relevant to many applications, including cellular manipulation, fluid dynamics, micro-robotics, and tests of fundamental physics.