Optical conveyor belt for delivery of submicron objects

We demonstrate an optical conveyor belt that provides trapping and subsequent precise delivery of several submicron particles over a distance of hundreds of micrometers. This tool is based on a standing wave (SW) created from two counter-propagating nondiffracting beams where the phase of one of the beams can be changed. Therefore, the whole structure of SW nodes and antinodes moves delivering confined micro-objects to specific regions in space. Based on the theoretical calculations, we confirm experimentally that certain sizes of polystyrene particles jump more easily between neighboring axial traps and the influence of the SW is much weaker for certain sizes of trapped object. Moreover, the measured ratios of longitudinal and lateral optical trap stiffnesses are generally an order of magnitude higher compared to the classical single beam optical trap. (c) 2005 American Institute of Physics.