Optical transport of semiconductor nanowires on silicon nitride waveguides

We investigate the behavior of silicon and ZnO nanowires in the evanescent field on the surface of a silicon nitride waveguide. The nanowires in aqueous solution are attracted to the waveguide by the gradient force and then propelled along the waveguide by the radiation pressure. Observed experimental velocities are higher for silicon nanowires than for ZnO nanowires, with relatively large variations for both kinds of nanowires. Simulations with the finite element method show that the forces on the nanowires are very dependent on their geometrical parameters and refractive index, which explains the observed variations.