MXene Nanoflakes Enabled All-Optical Nonlinear Activation Function for On-Chip Photonic Deep Neural Networks.

2D metal carbides and nitrides (MXene) are promising materials platform for on-chip neural networks owning to their nonlinear saturable absorption effect. The localized surface plasmon resonances in metallic MXene nanoflakes may play an important role in enhancing the electromagnetic absorption; however, their contribution has not been determined due to the lack of a precise understanding of its localized surface plasmon behavior. Here the saturable absorber made of MXene thin film and a silicon waveguide with MXene flakes overlayer are developed to perform neuromorphic tasks. The proposed configurations are reconfigurable and can therefore be adjusted for various applications without the need to modify the physical structure of the proposed MXene-based activator configurations via tuning the wavelength of operation. We confirm the capability and feasibility of the obtained results of machine-learning applications via handwritten digit classifications task, with near 99% accuracy. These findings can guide the design of advanced ultrathin saturable absorption materials on a chip for a broad range of applications. This article is protected by copyright. All rights reserved.