Optical Trapping, Optical Binding, and Rotational Dynamics of Silicon Nanowires in Counter-Propagating Beams

Silicon
nanowires are held and manipulated in controlled optical
traps based on counter-propagating beams focused by low numerical
aperture lenses. The double-beam configuration compensates light scattering
forces enabling an in-depth investigation of the rich dynamics of
trapped nanowires that are prone to both optical and hydrodynamic
interactions. Several polarization configurations are used, allowing
the observation of optical binding with different stable structure
as well as the transfer of spin and orbital momentum of light to the
trapped silicon nanowires. Accurate modeling based on Brownian dynamics
simulations with appropriate optical and hydrodynamic coupling confirms
that this rich scenario is crucially dependent on the non-spherical
shape of the nanowires. Such an increased level of optical control
of multiparticle structure and dynamics open perspectives for nanofluidics
and multi-component light-driven nanomachines.