Controlling the topological charge of twisted light beams with propagation

We report on advanced manipulation of a class of light beams---known as frozen waves---that carry orbital angular momentum and whose intensity and topological charge (sign and magnitude) can be controlled along the propagation direction, at will. Accordingly, we demonstrate rotating light structures that change their sense of rotation and order of phase twist with propagation. This degree of longitudinal control can address many challenges in dense data communications, optical trapping and micromanipulation, and remote sensing and imaging, to name a few.