Laser writing of parabolic micromirrors with a high numerical aperture for optical trapping and rotation

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 micrometer-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 three-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. (C) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).