Rotating particles in Laguerre–Gaussian beams. Particles (polystyrene, 1 μm radius) trapped in two concentric Laguerre–Gaussian beams with opposite helicity: the particles in the outer ring are pushed clockwise by a Laguerre–Gaussian beam with helicity +40, while the ones in the inner ring are pushed anticlockwise (at a faster angular speed) by a Laguerre–Gaussian beam with helicity −10. The particles are confined in a quasi-two- dimensional space by the scattering force that pushes them against the upper coverslip of the sample chamber.
Fig. 11.1 — Rotating particles in Laguerre-Gaussian beams