title: Measurement of the spiral spectrum of entangled two-photon states.
abstract: We implement an interferometric method to measure the orbital angular momentum (OAM) spectrum of photon pairs generated by spontaneous parametric down-conversion. In contrast with previous experiments, which were all limited by the modal capacity of the detection system, our method operates on the entire down-conversion cone and reveals the complete distribution of the generated OAM. In this geometry, new features can be studied. We show that the phase-matching conditions can be used as a tool to enhance the azimuthal Schmidt number and to flatten the spectral profile, allowing the efficient production of high-quality multidimensional entangled states.
authors.affiliation: Leiden University, Huygens Laboratory, P.O. Box 9504, 2300 RA Leiden, The Netherlands. pires@molphys.leidenuniv.nl
authors.forename: H
authors.initials: H
authors.lastname: Di Lorenzo Pires
authors.forename: H C B
authors.initials: HC
authors.lastname: Florijn
authors.forename: M P
authors.initials: MP
authors.lastname: van Exter