# Dual-mode optical fiber-based tweezers for robust trapping and manipulation of absorbing particles in air

## TL;DR

This paper introduces a dual-mode optical fiber tweezers system that effectively traps and manipulates absorbing particles in air using photophoretic forces, with enhanced performance over traditional single-mode setups.

## Contribution

The study presents a novel fiber-based optical tweezers design employing superposition of Hermite-Gaussian modes for improved particle trapping and manipulation in air.

## Key findings

- Achieved stable 3D trapping of absorbing particles for hours.
- Demonstrated manipulation velocities of ~5 mm/s axially and ~0.75 mm/s radially.
- Superposition mode improves trapping efficiency by around 80%.

## Abstract

We develop an optical tweezers system using a single dual-mode optical fiber where mesoscopic absorbing particles can be trapped in three dimensions and manipulated employing photophoretic forces. We generate a superposition of fundamental and first order Hermite-Gaussian beam modes by the simple innovation of coupling a laser into a commercial optical fiber designed to be single mode for a wavelength higher than that of the laser. We achieve robust trapping of the absorbing particles for hours using both the pure fundamental and superposition mode beams and attain large manipulation velocities of ~5 mm/s in the axial direction and ~0.75 mm/s in the radial direction. We then demonstrate that the superposition mode is more effective in trapping and manipulation compared to the fundamental mode by around 80%, which may be increased several times by the use of a pure first order Hermite-Gaussian mode. The work has promising implications for trapping and spectroscopy of aerosols in air using simple optical fiber-based traps.