Dark-hollow optical beams with a controllable shape for optical trapping in air.

A technique for generating dark-hollow optical beams (DHOBs) with a controllable cross-sectional intensity distribution is proposed and studied both theoretically and experimentally. Superimposed Bessel beams were used to generate such DHOBs. Variation of individual beam parameters enables the generation of Bessel-like non-diffracting beams. This technique allows the design of transmission functions for elements that shape both non-rotating and rotating DHOBs. We demonstrate photophoresis-based optical trapping and manipulation of absorbing air-borne nanoclusters with such beams.