Spiraling light: from donut modes to a Magnus effect analogy

The insight that optical vortex beams carry orbital angular momentum (OAM), which emerged in Leiden about 30 years ago, has since led to an ever expanding range of applications and follow-up studies. This paper starts with a short personal account of how these concepts arose. This is followed by a description of some recent ideas where the coupling of transverse orbital and spin angular momentum (SAM) in tightly focused laser beams produces interesting new effects. The deflection of a focused light beam by an atom in the focus is reminiscent of the Magnus effect known from aerodynamics. Momentum conservation dictates an accompanying light force on the atom, transverse to the optical axis. As a consequence, an atom held in an optical tweezer will be trapped at a small distance of up to lambda/2 pi away from the optical axis, which depends on the spin state of the atom and the magnetic field direction. This opens up new avenues to control the state of motion of atoms in optical tweezers as well as potential applications in quantum gates and interferometry.

Automated summary

The insight that optical vortex beams carry orbital angular momentum has led to a wide range of applications and studies. Recent research explores the coupling of transverse orbital and spin angular momentum in laser beams, leading to new effects like the deflection of light beams by atoms and the trapping of atoms at a small distance away from the optical axis. This research opens up new possibilities for controlling the motion of atoms in optical tweezers and potential applications in quantum gates and interferometry.