Pump depletion in optical parametric amplification

High-gain Spontaneous Parametric Down-conversion in Dispersive and Absorbing Nanostructured Systems

“…We emphasise that we are working in the undepleted pump approximation and thus assume the pump field to be an undepleted classical pulse, which is a crucial assumption for finding the input-output operator relations later in this work. Treating the extremely high-gain scenarios, in which the pump can also deplete substantially, results in a more complex dynamics for generation of non-Gaussian quantum states [57,58]. Advancing the GF formalism to go beyond the undepleted pump approximation could be an interesting direction for future works.…”