Abstract
All-optical spiking neural networks would allow high speed parallelized processing of time-encoded information,
using the same energy efficient computational principles as our brain. As the neurons in these networks need to
be able to process pulse trains, they should be excitable. Using simulations, we demonstrate Class 1 excitability
in optically injected microdisk lasers, and propose a cascadable optical spiking neuron design. The neuron has
a clear threshold and an integrating behavior. In addition, we show that the optical phase of the input pulses
can be used to create inhibitory, as well as excitatory perturbations. Furthermore, we incorporate our optical
neuron design in a topology that allows a disk to react on excitations from other disks. Phase tuning of the
intermediate connections allows to control the disk response. Additionally, we investigate the sensitivity of
the disk circuit to deviations in driving current and locking signal wavelength detuning. Using state-of-the-art
fabrication techniques for microdisk laser, the standard deviation of the lasing wavelength is still about one
order of magnitude too large. Finally, as the dynamical behavior of the microdisks is identical to the behavior
in Semiconductor Ring Lasers (SRL), we compare the excitability mechanism due to optically injection with the
previously proposed excitability due to asymmetry in the intermodal coupling in SRLs, as the latter mechanism
can also be induced in disks due to, e.g., asymmetry in the external reflection. In both cases, the symmetry
between the two counter-propagating modes of the cavity needs to be broken to prevent switching to the other
mode, and allow the system to relax to its initial state after a perturbation. However, the asymmetry due to
optical injection results in an integrating spiking neuron, whereas the asymmetry in the intermodal coupling is
known to result in a resonating spiking neuron.
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