title: Size selective trapping with optical "cogwheel" tweezers.
abstract: We experimentally investigate the size-selective trapping behavior of Laguerre-Gaussian beams ("doughnut-beams") and "cogwheel"-shaped beams which are collinear superpositions of two doughnut beams of equal opposite helical index. Experimentally they are created by diffraction of a Gaussian laser beam at a high resolution refractive spatial light modulator (SLM). In the focus of an optical microscope such a beam looks similar to a "cogwheel", i.e. the light intensity is periodically modulated around the circumference of a sphere with a precisely adjustable diameter. In an optical tweezers setup these modes can be used to trap particles or cells, provided their sizes exceed the ring diameter by a fixed amount. This promises a convenient method of constructing an optical tweezers system in microscopy which acts as a passive sorter for particles of differing sizes.
authors.forename: Alexander
authors.initials: A
authors.lastname: Jesacher
authors.forename: Severin
authors.initials: S
authors.lastname: Fürhapter
authors.forename: Stefan
authors.initials: S
authors.lastname: Bernet
authors.forename: Monika
authors.initials: M
authors.lastname: Ritsch-Marte