Ultrafast All‐Optical Switching

Ultrafast all‐optical switching, possessing the unique function of light controlling light, is an essential component of on‐chip ultrafast optical connection networks as well as integrated logic computing chips. Ultrafast all‐optical switching has attracted enormous research interests, the latest great developments of which have also yield progress in nanophotonics, integrated optics, nonlinear optics, material science, and optical communications, and so on. This review summarizes the fundamental realization principles, novel configurations, fancy materials, improved performance indexes, and ameliorated trigger method (transitioning from a traditional impractical free‐space‐vertical trigger to a more practical on‐chip trigger) of ultrafast all‐optical switching. Not only a systematic discussion of the current state‐of‐the art is provided, but also a brief outlook on the remaining challenges in the pursuit of the application of a practical on‐chip ultrafast all‐optical switching is also afforded. Ultrafast all‐optical switching, a core unit in on‐chip optical interconnection and ultrahigh speed information photonic chips, can control the propagation state of signal light. In this review, a summary of the fundamental concepts and mechanisms, composed structures, materials and outstanding performance indexes in all‐optical switching is provided. Different configurations are compared and an overview of the current research status and remaining challenges is given.