Orbital angular momentum, optical spanners, and rotational frequency shift

Abstract

Light possesses both spin and orbital angular momentum. Whereas the spin component arises from the spin of individual photons and is associated with circular polarization, the orbital component arises from the azimuthal component of the Poynting vector and is associated with helical wavefronts. The paper considers the generation of beams with orbital angular momentum, their interaction with matter, behavior in nonlinear media and frequency shifts arising from their rotation. In each case the properties of beams containing orbital and/or spin angular momentum is compared and explained.