All-Optical Diodes via Nonreciprocal Nonlinear Absorption and Interfacial Charge Transfer in Two-Dimensional van der Waals Heterostructures

Nonreciprocity is fundamental to photonic and optoelectronic devices, such as all-optical diodes, for ultrafast optical signal processing. However, previous studies on nonreciprocity have been mainly based on linear optical responses rather than on nonlinear optical responses in recently developed two-dimensional (2D) van der Waals heterostructures. Herein, an all-optical diode prototype based on nonreciprocal nonlinear absorption and interfacial charge transfer is proposed and designed using both simulations and experiments based on readily available van der Waals heterostructures. The giant saturable absorption from 2D MXenes (NbC) and reverse saturable absorption from 2D chalcogenides (GaS) play a synergistic role in the designed all-optical diodes, which are characterized by a femtosecond laser-based Z-scan system. The comprehensive physical mechanism of this all-optical diode based on a 2D van der Waals NbC/GaS heterostructure designed by simulations is consistent with experiments, considering both nonreciprocal nonlinear absorption and interfacial effects. This all-optical diode based on a 2D van der Waals heterostructure features simplicity, scalability, stability, integration, and compatibility with complementary planar fabrication technology, which can further extend and miniaturize nonlinear photonic and optoelectric devices.