Sigmoid Type Neuromorphic Activation Function Based on Saturable Absorption Behavior of Graphene/PMMA Composite for Intensity Modulation of Surface Plasmon Polariton signals

Abstract

For an optical technology to be feasible as a substitution of electronics one, it is required the waveguides be capable of confining and directing light signals in much smaller dimensions than the operating wavelength of the light, i.e. subwavelength optical components must be realized. One approach to miniaturize the size of the photonic components is to benefit the hybrid nature of Surface Plasmon Polariton which addresses the problem with the diffraction limit of regular photonic components. Here, the authors present a two-dimensional numerical simulation of a passive photonic element based on a saturable absorber material as an analogy to the biological neurons activation function. They demonstrate that at telecom wavelengths a highly confined SPP mode can be modulated in a nonlinear fashion by considering the carrier dynamics of graphene/PMMA polymeric composite as a two-level system. The sigmoid type nonlinear activation function derived from this study, further characterized and the parameters which appeared to be effective on the performance of the structure, such as saturation intensity, modulation depth, and thickness of the synaptic part as a Fabry-Perot structure, has been studied.

Optical Soliton Neural Networks

“…In the same year, D. Kuzum reported new nanoscale electronic synapses based on PCM for optical data storage and non-volatile storage [69]. Continuous resistance transitions in PCM [70] and saturable absorber composite materials are used to simulate the properties of biological synapses so as to realize synaptic learning rules [71]. In 2017, Alexander N. Tait of Princeton University published a paper referred to neuromorphic silicon photonics, introducing the world's first integrated photonic neural network [72], It uses a neural compiler to program a silicon photonic neural network with 49 nodes, each node operates at a specific wavelength, light from each node is detected and summed before it is fed into the laser, then the output will be feedback to create a feedback loop with nonlinear characteristics.…”