Optical trapping and sizing of aerosol droplets using counter-propagating Bessel beams

Two counter-propagating Bessel beams are used to create an optical trap to confine polydisperse aerosol droplets. A single arm can be used to optically guide droplets over macroscopic distances. Two opposing beams create a trapping region to optically confine particles over distances of 4mm. Droplets are optically trapped in the surrounding rings and the central core and are characterised using light scattering techniques. The elastically scattered fringe spacing from the 532nm trapping beam and from a 633nm probe beam are used to independently size droplets using Mie theory, as well as assessing the size from glare spots.