Programmable low-power consumption all-optical nonlinear activation functions using a micro-ring resonator with phase-change materials

Abstract

A programmable hardware implementation of all-optical nonlinear activation functions for different scenarios and applications in all-optical neural networks is essential. We demonstrate a programmable, low-loss all-optical activation function device based on a silicon micro-ring resonator loaded with phase change materials. Four different nonlinear activation functions of Relu, ELU, Softplus and radial basis functions are implemented for incident signal light of the same wavelength. The maximum power consumption required to switch between the four different nonlinear activation functions in calculation is only 1.748 nJ. The simulation of classification of hand-written digit images also shows that they can perform well as alternative nonlinear activation functions. The device we design can serve as nonlinear units in photonic neural networks, while its nonlinear transfer function can be flexibly programmed to optimize the performance of different neuromorphic tasks.

Simulation of waveguide integrated Ge2Sb2Te5-based tunable photodetector

“…[35][36][37] GST is selected as it exhibits high thermal stability, short tuning time (<30 ns), 38,39 and fast response time. As reported earlier, GST is employed in non-volatile 1 × 2 optical switching and multi-level memory, reversible all-optical switching, 40 tunable sensors, 41 tunable multichannel midinfrared optical filters, 42 biosensors to identify biomaterials including urine and hemoglobin, 43 programmable low-loss all-optical activation function devices, 44 and on-chip microphotonic wire switches. 45 In addition to this, GST-based photodetectors have been demonstrated to exhibit high responsivity, low dark current, and fast response time, [46][47][48] making them attractive to use in a variety of applications, including telecommunications, sensing, and imaging.…”

“…GST can be used in complex multilayer structures as it can be deposited at low temperature on any substrate or film and encourage to design tunable photonic devices for optical communication 55 – 58 It has been reported that by modifying the refractive index and extinction coefficient parameters of GST material, 59 its characteristics can be altered without changing the device structure and encourage its application in ring resonators, optical filters, 38 optical sensors, optical switches, silicon (Si) PICs, 39 and optical data storage systems 60 , 61 . Hence, much room is left for research in photodetection using materials like GST.…”