Advanced Progress on chi((3)) Nonlinearity in Chip-Scale Photonic Platforms

chi((3)) nonlinearity enables ultrafast femtosecond scale light-to-light coupling and manipulation of intensity, phase, and frequency. chi((3)) nonlinear functionality in micro- and nanoscale photonic waveguides can potentially replace bulky fiber platforms for many applications. In this Review, we summarize and comment on the progress on chi((3)) nonlinearity in chip-scale photonic platforms, including several focused hot topics such as broadband and coherent sources in the new bands, nonlinear pulse shaping, and all-optical signal processing. An outlook of challenges and prospects on this hot research field is given at the end.