From Event: SPIE OPTO, 2023
A final frontier of optical micromanipulation of mesoscopic particles in high-numerical aperture microscopes is the combination of displacement and rotation of single particles. In addition to the interesting challenge this presents, it is useful for the investigation of microscopic systems. Vaterite is a spheroidal birefringent particle used in optical micromanipulation for its ability to cause microscopic flow fields and measure the microenvironment surrounding it. It spins by changing the polarization of beam used to trap it. Typically, spinning vaterites can create a flow field with rotation axis in the direction of the beam axis. We show how light can be structured to allow optical trapping and rotation of vaterite—and other birefringent particles—around arbitrary axes, including those orthogonal to the average beam transmission axis! To achieve this effect, we use vector beam shaping produced using an interferometric technique resistant to changes in air currents and mechanical vibrations.
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Alexander B. Stilgoe, Naran Gillies, and Halina Rubinsztein-Dunlop, "Vector beam shaping for transverse angular momentum transfer," Proc. SPIE 12436, Complex Light and Optical Forces XVII, 1243602 (Presented at SPIE OPTO: January 30, 2023; Published: 15 March 2023); https://doi.org/10.1117/12.2657224.