Manipulation and filtration of low index particles with holographic Laguerre-Gaussian optical trap arrays

Multiple low index particles (micrometer-sized ultrasound contrast agent), have been optically trapped using a 4 x 4 Laguerre-Gaussian trap array. The trapping efficiency of the Laguerre-Gaussian arrangement was measured using a Stokes' flow approach whereby the critical relative fluid velocity required to remove particles from the optical trap was measured. The dependence of trapping efficiency on beam power was also explored and the optimum beam parameters were identified. Finally, the utility of the array as a selective filter was demonstrated by tweezing multiple low-index particles from a population exhibiting an inherent distribution in size. This procedure represents a unique remote non-contact process that may have significant applicability throughout the fields of biophysics and biotechnology. (C) 2004 Optical Society of America.