Alternative modes for optical trapping and manipulation using counter-propagating shapedbeams

Abstract

Counter-propagating beams have enabled the first stable three-dimensional optical trappingof microparticles and this procedure has been enhanced and developed over the years toachieve independent and interactive manipulation of multiple particles. In this work, weanalyse counter-propagating shaped-beam traps that depart from the conventionalgeometry based on symmetric, coaxial counter-propagating beams. We show thatprojecting shaped beams with separation distances previously considered axially unstablecan, in fact, enhance the axial and transverse trapping stiffnesses. We also show thatdeviating from using perfectly counter-propagating beams to use oblique beams canimprove the axial stability of the traps and improve the axial trapping stiffness. Thesealternative geometries can be particularly useful for handling larger particles. These resultshint at a rich potential for light shaping for optical trapping and manipulation usingpatterned counter-propagating beams, which still remains to be fully tapped.