Optical spin–orbit interaction in spontaneous parametric downconversion

Abstract

Optical spin–orbit interaction (SOI), which can be used to simultaneously control the spin and orbital angular momentum of light, is important for both classical and quantum information applications. In linear and nonlinear optics, the SOI of light has been extensively explored in both artificial structures and conventional optical crystals. However, optical SOI in quantum nonlinear optical processes, such as spontaneous parametric downconversion (SPDC), has not been studied before. Here, we experimentally demonstrate that optical SOI in the SPDC process can be realized through a nonlinear crystal with threefold rotational symmetry. Two-photon quantum states with controlled angular momentum can be generated through the symmetry selection rules in nonlinear optics and the SOI of the pump wave. The proposed methodology may facilitate the generation and control of spin and orbital angular momentum of entangled photons.

Nonlinear chiral metaphotonics: a perspective

“…19 Another very recent study demonstrated optical spin-orbit interaction in the SPDC process realized through a nonlinear crystal with threefold rotational symmetry. 100 Following these studies, we foresee a variety of theoretical and experimental studies of chirality in quantum light interaction with metastructures empowered by optical resonances.…”