Quasi-phase-matching engineering for spatial control of entangled two-photon states

We show that transverse engineering of quasi-phase-matched geometries can be used to tailor the spatial mode function that describes the quantum state of photon pairs generated in spontaneous parametric down-conversion. We study several geometries and reveal how properly engineered gratings affect, in particular, the spatial correlations embedded in two-photon entangled states. (C) 2004 Optical Society of America.