Particle delivery in generalized optical vortex conveyor belts with a uniform orbital flow

Perfect optical vortex (POV) beams offer a phase-gradient route to convey small particles along a tunable circular path or belt. The prevailing generalized POV method can be used to reshape the conveyor belt, but it usually deteriorates the orbital energy flow of field, leading to unstable conveying speed or even creating unwanted optical traps that prevent transportation. Here, we demonstrate optical conveyor belts with customized profiles and a uniform orbital flow over the whole transporting region by integrating isometric uniform sampling and random phases into the generalized POV generation algorithm. Smooth delivery of metallic particles, inaccessible to conventional generalized POV methods, is achieved at an almost even speed. We also demonstrate a dual-belt conveyor for delivering large metal microparticles, which experience repulsive intensity-gradient forces and thus are unable to be manipulated by a single belt. Our results present a unique addition to the toolbox of optical manipulation and would facilitate the development of small-scale drug delivery microsystems.