Rebecca Y. SaaltinkLambert GinerRobert W. BoydEbrahim KarimiJeff S. Lundeen2019-03-272019-03-2720161094-4087https://doi.org/10.20381/ruor-23234http://hdl.handle.net/10393/38984We propose a method for directly producing radially and azimuthally polarized photon pairs through spontaneous parametric downconversion (SPDC). This method constitutes a novel geometry for SPDC, in which a radially polarized Bessel-Gauss pump beam is directed into a nonlinear crystal, with the central propagation direction parallel to the crystal axis. The phasematching conditions are controlled by changing the opening angle of the pump beam; as the crystal axis cannot be tuned, we refer to this process as super-critical phasematching. We model and plot the spatial and polarization output distributions for Type-I and Type-II super-critical phasematching.enQuantum PhysicsQuantum PhysicsPhysics - OpticsArticle10.1364/OE.24.024495