Spatially Asymmetric Optical Propagation and All-Optical Switching Based on Spatial Self-Phase Modulation of Semimetal MoP Microparticles

Abstract

Molybdenum phosphide (MoP) has excellent catalytic activity in hydrogen evolution reactions, but research on its nonlinear optical properties is just beginning. In this work, the spatial self-phase modulation (SSPM) phenomena of semimetal MoP spherical microparticles are investigated, their applications in spatially asymmetric optical propagation and all-optical switching are developed. The effective nonlinear refractive index n₂ of MoP microparticles and the ring formation time τ_F of SSPM are measured to be about 10⁻⁵ cm² W⁻¹ and 0.4 s, respectively. The SSPM experimental results after the sample placed for over two months indicate that MoP microparticles have long-term stability and resistance to photodegradation. The physical origin of the interaction between light and MoP microparticles to form SSPM is dominated by laser-induced hole coherence and a small amount of thermal effect. By utilizing the superior optical nonlinearity of MoP microparticles, the spatially asymmetric optical propagation of MoP/violet phosphorus (VP) cascaded samples and the all-optical switching performance of MoP microparticles are demonstrated, respectively. These results deepen the understanding of the optical nonlinear mechanism of hole micromaterials and are beneficial for the development of SSPM based on topological semimetal micro/nano-materials in passive nonlinear photonic devices, such as all-optical diodes, optical isolators, optical logic gates, etc.