  We report a multi-modal spiking neuron that allows optical and electronic
input and control, and wavelength-multiplexing operation, for use in novel
high-speed neuromorphic sensing and computing functionalities. The
photonic-electronic neuron is built with a micro-scale, nanostructure resonant
tunnelling diode (RTD) with photodetection (PD) capability. Leveraging the
advantageous intrinsic properties of this RTD-PD system, namely highly
nonlinear characteristics, photo-sensitivity, light-induced I-V curve shift,
and the ability to deliver excitable responses under electrical and optical
inputs, we successfully achieve flexible neuromorphic spike activation and
inhibition regimes through photonic-electrical control. We also demonstrate the
ability of this RTD-PD spiking sensing-processing neuron to operate under the
simultaneous arrival of multiple wavelength-multiplexed optical signals, due to
its large photodetection spectral window (covering the 1310 and 1550 nm telecom
wavelength bands). Our results highlight the potential of RTD
photonic-electronic neurons to reproduce multiple key excitatory and inhibitory
spiking regimes, at high speed (ns-rate spiking responses, with faster sub-ns
regimes theoretically predicted) and low energy (requiring only ~10 mV and ~150
microW, electrical and optical input amplitudes, respectively), similar in
nature to those commonly found in the biological neurons of the visual system
and the brain. This work offers a highly promising approach for the realisation
of high-speed, energy-efficient photonic-electronic spiking neurons and spiking
neural networks, enabling multi-modal and multi-wavelength operation for
sensing and information processing tasks. This work therefore paves the way for
innovative high-speed, photonic-electronic, and spike-based neuromorphic
sensing and computing systems and artificial intelligence hardware.
