All-optical nonlinear activation functions based on germanium silicon hybrid integration

Abstract

Optical neural networks (ONNs), a kind of neural network implemented by optical hardware, have attracted more and more attention due to their excellent performance. As a part of ONNs, nonlinear activation functions the key for ONN to achieve more various functions. The realization of nonlinear activation functions by optical hardware has become a research hotspot. Here, we propose and demonstrate an all-optical implementation of a nonlinear activation function, which utilizes the intrinsic absorption and the plasma dispersion effect of germanium at 1550nm. The one has a loss about 4db and a threshold power of 5.1mW, while the another has a loss around 11db and a threshold power of 56.2mW. This proves that our scheme has great potential for nonlinear activation functions.