title: Circular motion of particles suspended in a Gaussian beam with circular polarization validates the spin part of the internal energy flow.
abstract: Non-spherical dielectric microparticles were suspended in a water-filled cell and exposed to a coherent Gaussian light beam with controlled state of polarization. When the beam polarization is linear, the particles were trapped at certain off-axial position within the beam cross section. After switching to the right (left) circular polarization, the particles performed spinning motion in agreement with the angular momentum imparted by the field, but they were involved in an orbital rotation around the beam axis as well, which in previous works [Y. Zhao et al, Phys. Rev. Lett. 99, 073901 (2007)] was treated as evidence for the spin-to orbital angular momentum conversion. Since in our realization the moderate focusing of the beam excluded the possibility for such a conversion, we consider the observed particle behavior as a demonstration of the macroscopic "spin energy flow" predicted by the theory of inhomogeneously polarized paraxial beams [A. Bekshaev et al, J. Opt. 13, 053001 (2011)].
authors.affiliation: Correlation Optics Department, Chernivtsi National University, Chernivtsi, Ukraine. angelsky@itf.cv.ua
authors.forename: O V
authors.initials: OV
authors.lastname: Angelsky
authors.forename: A Ya
authors.initials: AY
authors.lastname: Bekshaev
authors.forename: P P
authors.initials: PP
authors.lastname: Maksimyak
authors.forename: A P
authors.initials: AP
authors.lastname: Maksimyak
authors.forename: I I
authors.initials: II
authors.lastname: Mokhun
authors.forename: S G
authors.initials: SG
authors.lastname: Hanson
authors.forename: C Yu
authors.initials: CY
authors.lastname: Zenkova
authors.forename: A V
authors.initials: AV
authors.lastname: Tyurin
mesh_terms: D004867:Equipment Design; D007834:Lasers; D008027:Light; D008853:Microscopy / Q000379:methods; D015233:Models, Statistical; D008962:Models, Theoretical; D009038:Motion; D016011:Normal Distribution; D055095:Optics and Photonics; D010316:Particle Size; D010783:Photometry / Q000379:methods; D012542:Scattering, Radiation; D012666:Semiconductors