Laser Writing of Parabolic Micromirrors with a High Numerical Aperture for Optical Trapping and Rotation

TL;DR

This paper introduces a rapid, scalable laser ablation method to produce high-NA parabolic micromirrors for optical trapping and rotation, enabling cost-effective, customizable on-chip optical manipulation systems.

Contribution

A novel laser ablation technique for fabricating high-NA parabolic micromirrors with arbitrary sizes, suitable for scalable optical trapping and rotation applications.

Findings

Achieved a maximum trap stiffness of 52 pN/μm/W.

Fabricated over 350 micromirrors with controlled dimensions.

Demonstrated particle rotation using reflected circularly polarized light.

Abstract

On-chip optical trapping systems allow for high scalability and lower the barrier to access. Systems capable of trapping multiple particles typically come with high cost and complexity. Here we present a technique for making parabolic mirrors with micron-size dimensions and high numerical apertures (NA>1). Over 350 mirrors are made by simple CO2 laser ablation of glass followed by gold deposition. We fabricate mirrors of arbitrary diameter and depth at a high throughput rate by carefully controlling the ablation parameters. We use the micromirrors for 3-dimensional optical trapping of microbeads in solution, achieving a maximum optical trap stiffness of 52 pN/{\mu}m/W. We then further demonstrate the viability of the mirrors as in-situ optical elements through the rotation of a vaterite particle using reflected circularly polarized light. The method used allows for rapid and highly customizable fabrication of dense optical arrays.