Two properties of twisted-light absorption

We discuss two features of twisted-light absorption both by hydrogen-like atoms and by microparticles. First, we extend the treatment of atomic photoexcitation by twisted photons to include atomic recoil, derive generalized quantum selection rules, and consider phenomena of forbidden atomic transitions. In particular, we demonstrate that whatever part of the twisted photon's total helicity does not go into exciting the atomic state goes into making the atom as a whole revolve about the photon's symmetry axis. Second, using the same electromagnetic potential for the twisted light beams, we analyze the radiation pressure from these beams on micro-sized particles and verify that while the Poynting vector can in some circumstances point back toward the source, a complete analysis nonetheless gives a repulsive radiation pressure. (C) 2014 Optical Society of America