The recent progress of artificial intelligence (AI) has boosted the computational possibilities in
fields where standard computers are not able to perform. The AI paradigm is to emulate human
intelligence and therefore breaks the familiar architecture on which digital computers are based. In
particular, neuromorphic computing, artificial neural networks (ANN) and deep learning models
mimic how the brain computes. With this respect, photonics is a suitable platform to implement ANN hardware thanks to its speed, low power dissipation and multi-wavelength opportunities. One photonic device candidate to perform
as an optical neuron is the optical microring resonator. Indeed microring resonators show both a
nonlinear response and a capability of optical energy storage, which can be interpreted as a fading
memory. Here, we describe the physics of
silicon microring resonators and of arrays of microring resonators for application in neuromorphic
computing. We describe different types of ANNs from feed-forward networks to photonics extreme
learning machines and reservoir computing. In addition, we discuss also hybrid systems where silicon
microresonators are coupled to other active material
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