Navigating the classical-to-quantum transition in ultrafast nonlinear nanophotonics (Invited Paper)

Recent advances in nonlinear nanophotonics have enabled optical frequency conversion at energy scales remarkably close to the few-photon regime of quantum optics. A key technique in these efforts is dispersion engineering, allowing dynamical confinement of light into ultrashort pulses with high peak intensities. In this talk, we explore quantum effects expected to emerge in next-generation devices, with a focus on understanding how these phenomena interplay with the multimode physics of femtosecond pulses. Drawing inspiration from recent experiments in thin-film lithium-niobate nanophotonics, we present several numerical studies of broadband frequency conversion in chi(2)-nonlinear waveguides. Our analysis provides a detailed understanding of the dynamics and modal structure of quantum noise and entanglement, e.g., in parametric and supercontinuum generation. This talk also surveys some recent results we obtained for harnessing exotic quantum non-Gaussian states of light in ultrafast nonlinear nanophotonics. Proper engineering of these quantum effects may generate entirely new functionalities for nonlinear optics at and beyond the classical-quantum transition.