SPDC photon pairs using a spatially anti-symmetric pump beam in a ppLN ridge waveguide

In this paper, we study the possible parametric down-conversion processes in a type II phase-matched, Lithium Niobate ridge waveguide, designed to generate photon pairs in the telecommunication range. A quantum analysis of spontaneous parametric down-conversion (SPDC), first, with a pulsed Gaussian pump beam and second, with a pulsed, spatially anti-symmetric Hermite-Gaussian HG (1,0) pump beam predict the possible down conversion processes in each case. In case of the former, degenerate photon pairs are emitted at 1550 nm with the highest efficiency in the fundamental waveguide mode. While, in case of the latter, non-degenerate photon pairs in different higher-order spatial modes are generated. The joint spectral amplitude (JSA) analysis of these processes, prove that the generated photons pairs having orthogonal polarizations are negatively correlated. With multiple degrees of freedom, like polarization and spatial modes, such photons can be further harnessed towards modal-entangled and hyper-entangled photons for quantum information applications. This study involving the JSA is one of the first kinds, especially, to show the possibility of photon pairs generated in different spatial modes and polarization, after being incident with a spatially anti-symmetric pump beam in a ridge waveguide scenario.