Optically induced nanoparticle assemblies

Optical binding is a phenomenon that is exhibited by micro-and nano-particles systems, suitably irradiated with off-resonance laser light. When several particles are present, the effect commonly results in the formation of particle assemblies. In the optically induced potential energy surfaces responsible for such assembly formation, the location and intensity of local energy maxima and minima depend on the particle configurations with respect to the input beam polarization and Poynting vector. This paper reports the results of recent quantum electrodynamical studies on the energy landscapes for systems of three and more particles; the analysis of local minima allows determination of the energetically most favorable positions, and it shows how the addition of further particles subtly modifies each energy landscape. The analysis includes the identification and characterization of potential points of stability, as well as the forces and torques that the particles experience as a consequence of the throughput electromagnetic radiation. As such, the development of theory represents a rigorous and general formulation paving the way towards a fuller comprehension of nanoparticle assembly based on optical binding.