Polarization-resolved and polarization- multiplexed spike encoding properties in photonic neuron based on VCSEL-SA

Abstract

The spike encoding properties of two polarization-resolved modes in vertical-cavity surface-emitting laser with an embedded saturable absorber (VCSEL-SA) are investigated numerically, based on the spin-flip model combined with the Yamada model. The results show that the external input optical pulse (EIOP) can be encoded into spikes in X-polarization (XP) mode, Y-polarization (YP) mode, or both XP and YP modes. Furthermore, the numerical bifurcation diagrams show that a lower (higher) strength of EIOP is beneficial for generating tonic (phasic) spikes; a small amplitude anisotropy contributes to wide (narrow) tonic spiking range in XP (YP) mode; a large current leads to low thresholds of EIOP strength for both XP and YP modes. However, the spike encoding properties are hardly affected by the phase anisotropy. The encoding rate is shown to be improved by increasing EIOP strength. Moreover, dual-channel polarization-multiplexed spike encoding can also be achieved in a single VCSEL-SA. To the best of our knowledge, such single channel polarization-resolved and dual-channel polarization-multiplexed spike encoding schemes have not yet been reported. Hence, this work is valuable for ultrafast photonic neuromorphic systems and brain-inspired information processing.

Electrically Controlled Neuron-Like Spiking Regimes in Vertical-Cavity Surface-Emitting Lasers at Ultrafast Rates

“…In particular, VCSELs have attracted great research interest for use in neuromorphic photonics, given their inherent advantages, such as ultra-small footprint, low manufacturing cost, high-speed, potential for large scale integration and operation at telecommunication wavelengths, to name but a few [37,38]. The proposed use of VCSELs as artificial photonic neurons has seen the application of techniques such as polarization switching (PS) [39,40] and optical injection (OI) [26][27][28][29] [41][42][43][44][45][46] for the all-optical conversion of binary signals to spiking patterns. Perturbed OI has been used experimentally to demonstrate the controllable activation [41], and inhibition [42], of sub-ns excitable spike patterns in telecom-wavelength VCSELs with promising neuronal features.…”

“…Furthermore, recent numerical simulations, based on the spin-flip model [47], suggest that artificial VCSEL neurons subject to dual polarized injection may have potentially improved signal quality by avoiding undesirable relaxation oscillations [45]. Dual polarized optical injection has also demonstrated numerically the successful encoding of noise-robust spike signals in two polarization separated channels simultaneously [46].…”

Integrated Neuromorphic Photonics: Synapses, Neurons, and Neural Networks

“…[ 128,129 ] In addition, there have been multiple interesting numerical investigations on different interconnectivity architectures, learning algorithms, and network frameworks based on the PS operation of VCSEL neurons. [ 47,130–136 ]…”

Toward Neuromorphic Photonic Networks of Ultrafast Spiking Laser Neurons

“…Wavelength Experimental/ Numerical Spike activation via polarization switching [28,35] 1550 nm Experimental Spike activation via electrical bias stimulation [38] 1310 nm Experimental Spike activation via phase-modulated optical injection [29][30][31] 980 nm Experimental/ Numerical Spike activation via amplitudemodulated optical injection [37,[43][44] 1310 nm Experimental/ Numerical Spike inhibition via amplitudemodulated optical injection [39,43] 1310 nm Experimental/ Numerical Spike activation/inhibition via saturable absorber region [27,[47][48] 850 nm Numerical Networked/coupled spiking VCSELs [40][41][42]44] 1310 nm Experimental/ Numerical Nevertheless, to date the majority of works on SL-based photonic spiking neurons have focused on single devices. Yet, it is widely acknowledged that the implementation of interconnected architectures is needed to develop neuromorphic photonic systems for use in practical computing and Artificial Intelligence applications.…”

“…Also, an interesting work has very recently outlined the use of coupled VCSEL-arrays (at short-wavelengths) for use in neuromorphic applications [42]. Additionally, other works have numerically investigated different interconnectivity architectures between coupled VCSEL-Neurons (at telecom wavelengths) using PS for operation [43][44][45]. Further, theoretical works have also recently described the potentials of photonic neuronal models based on VCSELs with a saturable absorbing region in their structure and VCSELs in combination with vertical cavity semiconductor optical amplifiers, for different spiking processing tasks, including spiking memory, spike encoding, spike timing dependent plasticity and pattern recognition [27,[46][47][48][49].…”