Optical binding in non-diffracting beams

Abstract

Optical binding forces are present always when two and more colloidal particles are confined by external optical forces in a limited volume. They are caused by rescattering of the original incident field and they manifest themselves by a specific stationary displacements between confined micro-objects. Under certain circumstances the objects can self-organize into spatial arrangements creating so called optically bound matter. Detailed understanding of these forces might enable one to control this behavior. In this paper we present a theoretical study of the object self-organization in the field of two counter-propagating spatially incoherent non-diffracting beams. The field is uniform along the axis of propagation and so the studied phenomenon does not depend on the axial position of micro-objects. Therefore in this system the binding forces can be simply separated from the external forces of trapping field. We also compare this situation with setup of two counter-propagating Gaussian beams which are routinely used for studies of optical binding effects.