Dynamics of a microparticle levitated in vacuum by an optical vortex beam

Abstract

Levitated optomechanics is an emerging area of study enabled by optically trapped mesoscopic particles in vacuum. This opens the path to a range of new opportunities and insights at the classical-quantum interface. We review our recent work on the dynamics of an optically levitated microparticle in vacuum placed in an optical vortex beam. The dynamics are dictated by the orbital angular momentum of the field. The microparticle is confined within a Laguerre-Gaussian beam and orbits the annular beam profile with increasing angular velocity as the air drag force is reduced, as a result of reducing the background pressure. Furthermore, we extend this to explore the particle dynamics in a complex three- dimensional optical potential with orbital angular momentum in vacuum. The potential is formed by the generation of a“perfect vortex”beam, which upon propagation, evolves to a Bessel beam. We show that the optical gradient and scattering forces interplay with the inertial and gravitational forces acting on the trapped particle, which produces a rich variety of orbital motions with respect to the beam propagation axis.