Controlled Rotation of Optically Trapped Microscopic Particles

TLDR

The study demonstrates controlled rotation of optically trapped objects using a spiral interference pattern. The rotation is achieved by generating a spiral interference pattern from an annular laser beam and a reference beam, trapping objects in its arms, and rotating the pattern by altering the optical path length. Silica microspheres, glass rods, and chromosomes rotate at rates exceeding 5 Hz, and the method works independently of particle properties, enabling versatile optical and biological micromachines.

Abstract

We demonstrate controlled rotation of optically trapped objects in a spiral interference pattern. This pattern is generated by interfering an annular shaped laser beam with a reference beam. Objects are trapped in the spiral arms of the pattern. Changing the optical path length causes this pattern, and thus the trapped objects, to rotate. Structures of silica microspheres, microscopic glass rods, and chromosomes are set into rotation at rates in excess of 5 hertz. This technique does not depend on intrinsic properties of the trapped particle and thus offers important applications in optical and biological micromachines.