title: Interference from multiple trapped colloids in an optical vortex beam.
abstract: Laguerre-Gaussian (LG) beams are important in optical micromanipulation. We show that optically trapped microparticles within a monochromatic LG beam may lead to the formation of unique intensity patterns in the far field due to multiple interference of the forward scattered light from each particle. Trapped colloids create far field interference that exhibits distinct spiral wave patterns that are directly correlated to the helicity of the LG beam. Using two trapped particles, we demonstrate the first microscopic version of a Young's slits type experiment and detect the azimuthal phase variation around the LG beam circumference. This novel technique may be implemented to study the relative phase and spatial coherence of two points in trapping light fields with arbitrary wavefronts.
authors.affiliation: SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, United Kingdom. wml6@st-andrews.ac.uk
authors.forename: W M
authors.initials: WM
authors.lastname: Lee
authors.forename: V
authors.initials: V
authors.lastname: Garcés-Chávez
authors.forename: K
authors.initials: K
authors.lastname: Dholakia
mesh_terms: D000465:Algorithms; D003102:Colloids / Q000737:chemistry*; D004867:Equipment Design; D006696:Holography / Q000379:methods; D007834:Lasers; D008846:Micromanipulation / Q000295:instrumentation*; D008962:Models, Theoretical; D052898:Optical Tweezers; D055095:Optics and Photonics
chemical_list: D003102:Colloids