All-Optical Spiking Neuron Based on Passive Microresonator

Abstract

Neuromorphic photonics that aims to process and store information simultaneously like human brains has emerged as a promising alternative for the next generation intelligent computing systems. The implementation of hardware emulating the basic functionality of neurons and synapses is the fundamental work in this field. However, previously proposed optical neurons implemented with SOA-MZIs, modulators, lasers or phase change materials are all dependent on active devices and quite difficult for integration. Meanwhile, although the nonlinearity in nanocavities has long been of interest, the previous theories are intended for specific situations, e.g., selfpulsation in microrings, and there is still a lack of systematic studies in the excitability behavior of the nanocavities including the silicon photonic crystal cavities. Here, we report for the first time a universal coupled mode theory model for all side-coupled passive microresonators. Attributed to the nonlinear excitability, the passive microresonator can function as a new type of all-optical spiking neuron. We demonstrate the microresonator-based neuron can exhibit the three most important characteristics of spiking neurons: excitability threshold, refractory period and cascadability behavior, paving the way to realize all-optical spiking neural networks.

Recent progress of integrated circuits and optoelectronic chips

“…In the past decade, tremendous impressive exploratory studies have been completed, ranging from physical mechanisms, devices, architecture, algorithms, and systems to advance the field of photonic neuromorphic computing, as shown in Figure 17. From the device perspective, it has been proved that various optical devices can emulate the neuron-like [179][180][181] and synapse-like functions [182,183]. There have been numerous attempts to implement photonics spiking neurons like graphene excitable lasers, distributed feedback lasers, vertical-cavity surface-emitting lasers, or micropillars [174,178].…”

Integrated Neuromorphic Photonics: Synapses, Neurons, and Neural Networks

“…The LIF neuron has multiple unique properties. [ 103 ] 1) Excitability threshold: The LIF neuron can only fire an output spike when its potential exceeds a certain threshold. Moreover, there usually exists a steep transition in the response when below and above the threshold.…”

“…There have been some exciting researches on exploiting the excitability of passive microcavities to emulate the spiking dynamics of biological neurons. [ 103,138 ] There are various nonlinear effects, e.g., free‐carrier absorption (FCA), FCD, thermo‐optic (TO) effect, interacting with each other in a microcavity. Among them, the FCD effect leads to a blue shift in the resonance wavelength, whereas the TO effect induces a red shift in the resonance.…”

“…The nonlinear dynamics of a passive side‐coupled microresonator can be characterized by a set of coupled‐mode theory (CMT) equations. [ 103 ] where is the complex amplitude of the forward and backward propagation mode, respectively, and stands for the corresponding mode energy in the microresonator. represents the complex amplitude of the pump light and the perturb...…”

“…[ 138 ] However, leaky integrating, inhibitory properties of nanobeams are further numerically simulated, as shown in Figure 14e–f. [ 103 ] The passive nanobeam neuron has the potential to be a competitive alternative in implementing large‐scale on‐chip neuromorphic processors with operation speed on the timescale of nanosecond and power consumption on the order of microwatt.…”