Hierarchical Optical Waveguides Based on Serpentine-Like Organic Pseudo-Plastic Crystals that Mimic Neural Networks

Optical components and circuits for signal generation and processing are essential for artificial neural networks (ANNs). We present an interconnected, four-layered organic crystal optical waveguide architecture that mimics an ANN. This structure is constructed from pseudo-plastic organic crystals of (E)-1-(((5-methylpyridin-2-yl)imino)methyl)naphthalene-2-ol (MPyIN) using an atomic force microscopy (AFM) cantilever tip-based micromanipulation technique. By strategically selecting four MPyIN crystal waveguides of varying lengths, bending them into serpentine-like forms, and integrating them hierarchically, we create interconnected, neuron-like optical waveguides with six optical synapses. These synapses enable parallel transmission of passive optical signals through evanescent coupling across multiple paths within the waveguides. The feedforward mechanism allows the synapses to split the input optical signal into four diverging signals with different magnitudes. Certain outputs deliver mixed passive and active signals due to diverging and converging optical paths. This hierarchical, ANN-like architecture offers a foundation for developing smart optical neural networks using multiple emissive and phase-changing organic crystals.