Bidirectional optical learnable neural networks for OEIC

A novel configuration of an optical bidirectional learnable neural network is proposed, in which the recall and learning processes can be done by transmitting lights of synaptic weight and error signal, respectively, in the opposite direction between two facing OEICs (optoelectronic integrated circuits). Thus, both vector-matrix operation for recall and outer-product for modifying synaptic weights are optically performed bidirectionally. This compact configuration is especially suitable for neurochips. The feasibility of a three-dimensional neurochip is experimentally investigated based on a learning experiment using a 2×2 optical neuro-breadboard