Color-Recognizing Si-Based Photonic Synapse for Artificial Visual System

Recently, photonic synapses that can directly respond to light signals have attracted much attention due to their huge application potential in neuromorphic chips and artificial vision systems. However, the implementation of an artificial visual system based on a synapse remains a considerable challenge due to the limitation that most current photonic synapses fail to recognize color. Here, a photonic synapse with color recognition capability is proposed and demonstrated. Through the light-induced adjustment of dangling bond defects inside the amorphous silicon (a-Si) film, the device exhibits switchable volatile and nonvolatile photoconductivity (PC) behaviors at the wavelengths of 635 and 450nm, respectively. Based on the dual PC, the photonic synapse enables dual synaptic plasticity depending on the stimulation light, allowing not only various synaptic functions, but also learning experiences, associative learning behaviors, and recognition of the red and blue colors. Moreover, the dual synaptic plasticity of the photonic synapse could be modulated via a voltage in the range below approximate to 1V to realize the stable detection and precise extraction of the grayscale and color signals. With its simple structure and compatibility with existing Si-complementary metal oxide semiconductor (CMOS) technology, this photonic synapse shows potential for application in neuromorphic computing and advanced robot vision systems.