title: Reverse orbiting of microparticles in optical vortices.
abstract: We report the observation of particles trapped at an air-water surface orbiting in a reverse direction with respect to the orbital angular momentum of the light field. The effect is explained by a combination of asymmetric particle shape and confinement of the particle on the 2D air-water interface. The experiment highlights the strong influence of the particle shape on the momentum transfer, an effect that is often not considered in optical trapping experiments.
authors.affiliation: Division for Biomedical Physics, Innsbruck Medical University, Innsbruck, Austria. Alexander.Jesacher@i-med.ac.at
authors.forename: A
authors.initials: A
authors.lastname: Jesacher
authors.forename: S
authors.initials: S
authors.lastname: Fürhapter
authors.forename: C
authors.initials: C
authors.lastname: Maurer
authors.forename: S
authors.initials: S
authors.lastname: Bernet
authors.forename: M
authors.initials: M
authors.lastname: Ritsch-Marte