  Excitable optoelectronic devices represent one of the key building blocks for
implementation of artificial spiking neurons in neuromorphic (brain-inspired)
photonic systems. This work introduces and experimentally investigates an
opto-electro-optical (O/E/O) artificial neuron built with a resonant tunnelling
diode (RTD) coupled to a photodetector as a receiver and a vertical cavity
surface emitting laser as a the transmitter. We demonstrate a well defined
excitability threshold, above which this neuron produces 100 ns optical spiking
responses with characteristic neural-like refractory period. We utilise its
fan-in capability to perform in-device coincidence detection (logical AND) and
exclusive logical OR (XOR) tasks. These results provide first experimental
validation of deterministic triggering and tasks in an RTD-based spiking
optoelectronic neuron with both input and output optical (I/O) terminals.
Furthermore, we also investigate in theory the prospects of the proposed system
for its nanophotonic implementation with a monolithic design combining a
nanoscale RTD element and a nanolaser; therefore demonstrating the potential of
integrated RTD-based excitable nodes for low footprint, high-speed
optoelectronic spiking neurons in future neuromorphic photonic hardware.
