Photonic Synapses for Ultrahigh‐Speed Neuromorphic Computing

Neuromorphic computing based on a non‐von Neumann architecture is a promising way for the efficient implementation of artificial intelligence. A neuromorphic computing system is mainly composed of artificial synapses and neurons. Various electronic neuromorphic devices have been developed by different technologies. Neuromorphic photonics combines the efficiency of neural networks and the speed of photonics to build computing systems. Compared with their electronic counterparts, photonic neurons and synapses have the potential advantages of ultrafast operation speed, large bandwidth, and no electrical interconnect power loss, inherent to the computing by optical means. Therefore, photonic neuromorphic devices are attracting more and more attention. This work reviews the recent advances in the development of photonic synapses. Both purely photonic synapses and photoelectric synapses are described. Their structures and working mechanisms are discussed in detail.