title: Laser trapping of small colloidal particles in a nematic liquid crystal: clouds and ghosts.
abstract: We show that, contrary to intuition, small (< or =1 microm) transparent particles can be trapped and manipulated in a nematic liquid crystal using an intense laser beam, although their index of refraction is lower than both refractive indices of the surrounding birefringent fluid. Two mechanisms are identified that are responsible for this anomalous trapping: (i) surface-induced distortion of the birefringent media around the particle, creating a high-index "cloud" around the colloid, and (ii) laser-induced distortion or (partial) melting of a nematic, creating a ghost colloid.
authors.affiliation: J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia and Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia. igor.musevic@ijs.si
authors.forename: I
authors.initials: I
authors.lastname: Musevic
authors.forename: M
authors.initials: M
authors.lastname: Skarabot
authors.forename: D
authors.initials: D
authors.lastname: Babic
authors.forename: N
authors.initials: N
authors.lastname: Osterman
authors.forename: I
authors.initials: I
authors.lastname: Poberaj
authors.forename: V
authors.initials: V
authors.lastname: Nazarenko
authors.forename: A
authors.initials: A
authors.lastname: Nych