Amorphous MetalSulphide Microfibers Enable Photonic Synapses for BrainLike Computing

635 wileyonlinelibrary.com C O M M U N IC A IO N of particular interest as their physical properties can be temporarily or permanently altered with light, thus giving the opportunity to provide similar conditions to propagating optical signals that exists for biochemical and electrical signal transduction in the brain. [ 18–21 ] The “photonic axon and synapse” proposed here is based on the gallium lanthanum oxysulphide (GLSO) fi ber. Here, photodarkening manifests itself as a volatile (transient) and nonvolatile (metastable) broadband reduction of transmissivity of the fi ber resulting from a fl ash of illumination at a subbandgap optical frequency. While the transient changes rapidly decay upon switching off the illumination, metastable photodarkening is permanent, but is reversible by annealing. [ 22–26 ]