We elucidate the paraxial orbital angular momentum of entangled photon pairs generated by spontaneous parametric downconversion in different noncollinear geometries in which the entangled photons counterpropagate. We find, in particular, the orbital angular momentum of entangled pairs generated in transverse-emitting configurations, in which none of the known rules for selecting orbital angular momentum holds.
© 2004 Optical Society of America
Juan P. Torres, Clara I. Osorio, and Lluis Torner, "Orbital angular momentum of entangled counterpropagating photons," Opt. Lett. 29, 1939-1941 (2004)