Divergence of single photons with different orbital angular momentum

The optical vortex beams have attracted a great deal of interest in recent times due to their wide range of applications in classical and quantum optics [1] . Due to the presence of the orbital angular momentum (OAM) per photon and the doughnut-shaped intensity distribution, the optical vortices have been used for a variety of studies with free space propagation [2] . While the propagation dynamics of the classical optical vortices have been studied in the literature, there is no such study for the single photons carrying OAM. Here we report on the experimental measurement of divergence of single-photon carrying OAM.