Bifocal Optical-Vortex Lens with Sorting of the Generated Nonseparable Spin-Orbital Angular-Momentum States

Abstract

In an optical vortex beam, each photon carries orbital angular momentum (OAM), a useful resource for applications in optical communication and quantum information processing. The authors demonstrate a diffractive bifocal vortex lens that generates and sorts light beams of different OAM, by means of polarization control. Placing the lens inside a cavity, a vortex-beam laser with a chosen OAM can be realized. Moreover, the lens's OAM sorting can be used in a multifocal optical-trapping system that facilitates the manipulation of nanoparticles, molecules, and biological samples.