Abstract: Strongly-driven nonlinear optical processes such as spontaneous parametric down-conversion and spontaneous four-wave mixing can produce multiphoton nonclassical beams of light which have applications in quantum information processing and sensing. In contrast to the low-gain regime, new physical effects arise in a high-gain regime due to the interactions between the nonclassical light and the strong pump driving the nonlinear process. Here, we describe and experimentally observe a gain-dependent group delay between the multiphoton pulses generated in a high-gain type-II spontaneous parametric down-conversion source. Since the group delay introduces distinguishability between the generated photons, it will be important to compensate for it when designing quantum interference devices in which strong optical nonlinearities are required. Joint work with Guillaume Thekkadath, Martin Houde, Duncan England and Ben Sussman. Co-sponsored by: INRS Optica-SPIE Student Chapter Speaker(s): Nicolás Quesada Room: Salle Tudor Johnston, Bldg: INRS-EMT, 1650 Boulevard Lionel-Boulet, Varennes, Quebec, Canada, J3X 1P7, Virtual: https://events.vtools.ieee.org/m/418357