Neuronal emulation can be either investigated employing digital simulations or neuromorphic modules which express the dynamics of the neuronal systems directly on an analogous physical substrate. Digital simulations suffer the disadvantage that they are cast on abstract binary electronic circuits whose operation is entirely divorced from the physical processes being simulated. Therefore, the ability to produce pulses that mimic in a physical substrate the biological spikes of neuronal systems has been recently extensively investigated in both electronics and laser systems with promising applications in photonics such as clock recovery and pulse reshaping, and artificial neural networks using spiking processing.
Spiking processing employing bursting, or spiking signals, where information is encoded as events in time is an outstanding phenomenon attracting continued attention over the years driven by excitable systems as diverse as, for example, the cells responsible for vital neurological rhythmicity, mixed-mode oscillations of chemical systems, and all sorts of intensity spiking observed in laser systems. Excitable systems provide an all-or-none response to external stimuli: the system responds linearly and with small amplitude to stimuli that do not overcome a threshold, but otherwise it yields a large pulse (whose shape is independent of the stimulus) followed by a lapse, called the refractory time, during which the system does not respond to new stimuli.
In this work, we report the generation of ultrafast spiking and bursting signals characteristic of biological neuronal bursting phenomena employing a compact hybrid integrated optoelectronic oscillator (OEO) circuit. The OEO system operatesin the framework of the excitability concept, and can be sensitively controlled in both the electrical and the optical domains. It is formed by a double barrier quantum well (DBQW) resonant tunneling diode (RTD) photo-detector driving a commercial communications laser diode. The resonant tunneling diode provides a non-monotonic current-voltage characteristic with a region of negative differential resistance that confers the resonant tunneling diode excitable properties. At the same time, its nanoscale DBQW structure allows for extreme compactness and high-speed operation.
Our system possesses the inherent capabilities for being used in the framework of bio-inspired data processing in electro-optical systems: a high potential for fully monolithic integration, an intrinsic high-speed response and quadruple electronic and optical inputs/outputs. Potential uses of our excitable system include ultra-fast neuronal-inspired data processing, similar to reservoir computing, switching in optical networks, and also neuronal emulation applications such as associative memory or cellular neural network-based computing architectures to perform complex parallel information processing.
Opt Express. 2013 ;21(18):20931-40.
Romeira B, Javaloyes J, Ironside CN, Figueiredo JM, Balle S, Piro O.
We demonstrate, experimentally and theoretically, excitable nanosecond optical pulses in optoelectronic integrated circuits operating at telecommunication wavelengths (1550 nm) comprising a nanoscale double barrier quantum well resonant tunneling diode (RTD) photo-detector driving a laser diode (LD). When perturbed either electrically or optically by an input signal above a certain threshold, the optoelectronic circuit generates short electrical and optical excitable pulses mimicking the spiking behavior of biological neurons. Interestingly, the asymmetric nonlinear characteristic of the resonant tunneling diode -laser diode allows for two different regimes where one obtain either single pulses or a burst of multiple pulses. The high-speed excitable response capabilities are promising for neurally inspired information applications in photonics.