S. Hanna (17 decembre 2019)

Optical binding was first observed between spherical particles around thirty years ago. Optical binding forces can result in various geometric arrangements of colloidal matter into regular, crystalline arrays and can induce complex, non-conservative and quasi-periodic motions. Although most studies of optical binding have focussed on dielectric spheres, recent departures from this trend have included silver bipyramids, nanowires and chiral particles. With reduction of particle symmetry comes extra complexity: torques can be applied to non-spherical objects by the applied beam, as well as by the scattered field from neighbouring particles. Another way to lower the symmetry of the system is if the optical binding itself results in the formation of a lower symmetry cluster. The resulting cluster may then interact with the angular momentum of the beam, generating non-conservative, quasi-cyclic motion. When large numbers of particles are present in the optical trap, the precise natures of the motions become hard to predict. In this talk, I will present the results of computer simulations used to explore the dynamical behavior of optically bound clusters of spherical and non-spherical nanoparticles. Predictions will include both rotatory and translational motions, which might eventually find application in optically driven micro-machines or optically driven swimmers.