Demonstration of Spatial Asymmetric Light Propagation Performance Using Violet Phosphorus Quantum Dots with Tunable Bandgap

Abstract The spatial self‐phase modulation (SSPM) of phosphorus‐based nanomaterials is widely studied and developed as passive nonlinear photonic devices for applications in all‐optical switches, logic gates, information converters, etc. In this work, violet phosphorus quantum dots (VP QDs) are prepared and characterized in three different solvents, their SSPM is investigated, and their spatial asymmetric light propagation performances are demonstrated. It is shown that VP QDs prepared in three different solvents exhibit different bandgaps, mainly due to the interaction between the dangling bonds of VP QDs and functional groups in different solvents. The SSPM experiment characterizes the nonlinear optical response of solvent‐dependent VP QDs. It is found that VP QDs exhibit strong nonlinear optical effect and their nonlinear refractive indexes are comparable to other phosphorus‐based 2D materials. Unlike the previously reported principle of spatial asymmetric light propagation (i.e., a cascaded sample based on SSPM composed of nanomaterials with excellent nonlinear refraction and SnS 2 with reverse saturation absorption), the spatial asymmetric light propagation performance based on SSPM is demonstrated using a cascaded sample of VP QDs with significantly different nonlinear optical response prepared in two different solvents.