Integrated van der Waals waveguides for all-optical nonlinear photonic circuits.

All-optical deep neural networks offer significant improvements in processing speed and energy efficiency compared with traditional electronic systems. However, achieving broadband all-optical signal transmission with ultrafast processing speed in conventional photonic waveguides remains challenging. In this work, we present an integrated photonic circuit incorporating vertically grown molybdenum disulfide (MoS2), which is also compatible with wafer-scale manufacturing. By leveraging the saturable absorption properties of MoS2, this platform enables all-optical nonlinear activation over both the telecommunication O-band and C-band, with response speeds as fast as ~ 10 ps. This broadband operability enables flexible deployment as an optical activation function for neural network inference. Using a standardized evaluation framework, we benchmarked task-level performance against mainstream digital activation functions across diverse network architectures and quantization settings. These findings highlight the potential of van der Waals materials like MoS₂ for enabling in-situ nonlinearity in all-optical neural network hardware, advancing the development of scalable photonic computing systems.