Spin-orbit optomechanics of optically levitated chiral Bragg microspheres

摘要

We explore the spin-orbit nature of the optical torque exerted on chiral liquid-crystal microspheres exhibiting circular Bragg reflection. Experimental investigation relies on the direct optomechanical observation of spinning liquid-crystal droplets immersed in water and held in a circularly polarized laser levitator. More generally, we anticipate that the total angular momentum transfer per photon may depart from the commonly assumed spin-only ±2 h contribution, when the topological features of the illuminated microsphere are taken into account.