Nonlinear Nanophotonics in Thin-Film Lithium Niobate: How Many Octaves, How Few Photons?

Nonlinear frequency conversion in lithium niobate waveguides has long been exploited as a means for extending the operating wavelength range and pulse durations/spectral bandwidth of available laser sources. Other applications have included classical and quantum optical signal processing, and generation of nonclassical states of light. Over the past half decade, the emergence of thin-film lithium niobate (TFLN) as a platform for nonlinear nanophotonics has greatly expanded the design space for these devices: The tight optical confinement in TFLN is enabling in several regards: orders of magnitude reductions in the required pump powers, dispersion engineering for ultra-broadband (even multi-octave) operation, and compact devices along with tight bends for dense multi-function integration. The combination of these degrees of freedom has led to a resurgence of interest in guided-wave nonlinear interactions.