Optically evolved assembling of polystyrene microparticles at dye solution surface: application toward an optically reconfigurable random laser

In the present work, we study optical trapping of two kinds of trapping targets together, 20 μm and 1 μm PS MPs, at the solution surface. The resulting assembly has a unique structure, that 1 μm PS MPs form a belt surrounding to a single 20 μm PS MP as the body, and 3-dimensionally grows more than 50 μm in diameter even though the trapping laser focus size is only 1 μm. We further demonstrate that the optically prepared light scattering assembly can serve as a unique reconfigurable random lasing medium. As the assembly is prepared exclusively where and when trapping laser is irradiated, our study will offer a new tool for studying optically reconfigurable and tunable disordered photonics.