Beyond photon pairs-nonlinear quantum photonics in the high-gain regime: a tutorial

Integrated optical devices will play a central role in the future development of nonlinear quantum photonics. Here we consider the generation of nonclassical states of light within them with a focus on Gaussian states beyond the low-gain, single photon pair regime accurately described by perturbation theory. Starting from the solid foundation provided by Maxwell's equations, we then move to applications by presenting a unified formulation that allows for a comparison of stimulated and spontaneous experiments in ring resonators and nanophotonic waveguides and leads directly to the calculation of the quantum states of light generated in high-gain nonlinear quantum photonic experiments.(c) 2022 Optica Publishing Group