Manipulation of low-refractive-index particles using customized dark traps

Low-refractive-index particles play significant roles in physics, drug delivery, biomedical science, and other fields. However, they have not attained sufficient utilization in active manipulation due to the repulsive effect of light. In this work, the establishment of customized dark traps is demonstrated to fulfill the demands of versatile manipulation of low-refractive-index particles. The customized dark traps are generated by assembling generalized perfect optical vortices based on the free lens modulation method, by which the beams’ shape, intensity, and position can be elaborately designed with size independent of topological charge. Using the customized dark traps with high quality and high efficiency, rotation along arbitrary trajectories with controllable speed, parallel manipulation, and sorting of low-refractive-index particles by size can be realized. With unprecedented flexibility and quality, the customized dark traps provide tremendous potential in optical trapping, lithography, and biomedicine.