Dynamic formation of arrays of interacting optical spatial solitons under light-sheet illumination.

Colloidal suspensions of micron- and submicron-sized particles act as effective nonlinear media that can self-arrange into intricate static or dynamic structures upon illumination with a laser beam. Optical spatial solitons (OSSs) represent a prominent example of such light-induced structures. We study the formation of two-dimensional arrays of interacting OSSs from colloidal particles of varying sizes illuminated by counter-propagating light-sheet beams. We monitor evolution of growing OSS arrays upon addition of individual constituent particles and show that a small change in the total number of particles in the structure can induce long-range reconfiguration of the overall OSS layout. In particular, the minimal distance between the neighboring OSSs in the array is observed to nearly linearly increase with increasing number of constituent particles. Our experimental observations are semi-quantitatively supported by theoretical modeling based on the rigorous multiple Mie scattering theory.