Electrodynamic mechanism and array stability in optical binding

Addressing optically induced interactions between nanoparticles, new results from quantum electrodynamical studies are employed to produce surfaces representing the variation of potential energy with the various geometric degrees of freedom – the positions and orientations of each particle relative to each other, and to the throughput radiation. The results take the form of energy landscapes exhibiting highly detailed topographic features. The analysis of these features facilitates the determination of possible stability points associated with optical binding, and the identification of other, anisotropic features revealing the operation of local forces and torques. Extending previous theory, the present study gives results for both polarized and non-polarized light, also providing a critical analysis of the significance of multipole interactions. It is shown that the pair potential provides a prototypical template for the optical assembly of larger numbers of particles, and a discussion is given of the possibilities to optically fabricate structures using polarized or non-polarized laser beams. The results are applicable to optically trapped molecules, nanoparticles, microparticles, colloids, etc.