An artificial synapse that operates entirely with light—using optical signals for both receiving information and updating its internal state—has been developed by researchers, marking a significant step toward neuromorphic computing.
The device is built from a rare-earth-doped crystal that emits a persistent afterglow after illumination, storing optical information via trapped charge carriers.
It exhibits paired-pulse facilitation under ultraviolet light and paired-pulse depression under near-infrared light, mimicking short-term synaptic plasticity without electrical control.
A model was developed to explain the behavior, which matched experimental measurements.
The material was combined with a silicon imaging sensor to create a neuromorphic camera prototype that performs in-sensor processing, enhancing contrast and reducing noise.
In a neural network simulation using the device's measured behavior, image recognition accuracy on handwritten digits improved to 95.99% after denoising, compared to about 78% without.
The study was published in Advanced Photonics (doi: 10.1117/1.AP.8.4.046001).