On‐Chip Optoelectronic Synapse Based on Embedded Amorphous Carbon in Lithium Niobate‐on‐Insulator

Abstract Lithium niobate on insulator (LNOI) wafers serve as a fundamental photonic platform for photonic integrated circuits. However, their application in photonic neural networks is limited due to a lack of optoelectronic properties, necessitating complex heterogeneous integration. This work proposes a novel integration scheme that embeds heterogeneous structures within LNOI using ion implantation to achieve broadband optoelectronic functionalities (photovoltaic and persistent photo‐conductivity) for mimcking synaptic functions for Pavlovian‐type associative learning. Implanted carbon ions form an AC layer embedded in a lithium niobate layer (AC – LNOI), characterized by conductivity and wide‐spectrum light absorption. Upon illumination, the AC generates photo carriers, endowing AC‐LNOI with the persistent photo‐conductivity, which is employed as an artificial synapse to mimic synaptic functionalities. This work demonstrates the embedded heterogeneous integration as an efficient avenue to reduce the complexity within artificial neural network learning systems based on photonic integrated circuits.