Vortex beam: generation and detection of orbital angular momentum [Invited]

Recent advances in the research of vortex beams,structured beams carrying orbital angular momentum(OAM),have revolutionized the applications of light beams,such as advanced optical manipulations,high-capacity optical communications,and super-resolution imaging.Undoubtedly,the methods for generation of a vortex beam and detection of its OAM are of vital importance for the applications of vortex beams.In this review,we first introduce the fundamental concepts of vortex beams briefly and then summarize approaches to generating and detecting the vortex beams separately,from bulky diffractive elements to planar elements.Finally,we make a concise conclusion and outline that is yet to be explored.

Measuring high orbital angular momentum of vortex beams with an improved multipoint interferometer

A multipoint interferometer(MI),uniformly distributed point-like pinholes in a circle,was proposed to measure the orbital angular momentum(OAM)of vortex beams[Phys.Rev.Lett.101,100801(2008)],which can be used for measuring OAM of light from astronomical sources.This is a simple and robust method;however,it is noted that this method is only available for low topological charge because the diffracted intensity patterns for vortex beams with higher OAM will repeat periodically.Here,we propose an improved multipoint interferometer(IMI)for measuring the OAM of an optical vortex with high topological charge.The structure of our IMI is almost the same as the MI,but the size of each pinhole is larger than a point in the MI.Such a small change enables each pinhole to get more phase information from the incident beams;accordingly,the IMI can distinguish any vortex beams with different OAM.We demonstrate its viability both theoretically and experimentally.