Tunable Optical Nonlinearities in Layered Materials

Nonlinear optical processes lie at the heart of frequency tunable coherent light sources, including entangled photon sources and squeezed states of light, and they have become ubiquitous in fields ranging from ultrafast spectroscopy to quantum information processing. van der Waals materials have recently emerged as dynamically tunable and highly nonlinear optical platforms with ultracompact footprints. In particular, semiconducting materials like transition metal dichalcogenides possess large optical nonlinearity, orders of magnitude higher than standard nonlinear bulk crystals, and promise interesting opportunities toward the miniaturization of nonlinear optical devices down to the nanoscale. In this Perspective, we outline ongoing and future research directions in the field of nonlinear optics with layered semiconductors, with special focus on the control and tunability of their optical nonlinearities.