Mingzhou Chen, Michael Mazilu, Yoshihiko Arita, Ewan M. Wright and Kishan Dholakia.
Optical Review 22(1), 162-165 (2015)
We experimentally create a ‘perfect’ vortex beam, which has a uniform ring profile and fixed radius. In contrast with other vortex fields, the intensity profile is independent of its topological charge. We then correct this field in situ using a single trapped particle as a probe. This results in a constant angular velocity for the particle regardless of its position on the beam circumference.