Abstract

Some light beams rotate as they propagate. If it is not the polarization vector, but the phase structure that rotates, the beam is said to carry orbital angular momentum (OAM). Such beams exhibit a helical phase front, where the phase rotates around a symmetry center. Because the phase in the center is undefined (and the intensity there is therefore zero), it is often termed a phase singularity or optical vortex by analogy to superfluidic vortices. Vortex beams [1,2] and more specifically ultrashort (few cycle) vortex pulses [3] have recently attracted strong interest.

© 2015 IEEE