Optical bistability of photonic spin Hall effect in SPR-enhanced plasmonic structures

We propose a multilayer structure composed of a Ge₂₀Ga₅Sb₁₀S₆₅ (2S2G) chalcogenide prism, a gold layer, and a nonlinear material layer. Surface plasmon resonance (SPR) at the Au-nonlinear interface is excited by p-polarized light through the prism, inducing local field enhancement and nonlinear effects. Numerical simulations are performed to analyze the reflection and transmission coefficients, as well as the transverse shift, revealing a bistable response (i.e., the system exhibits two distinct output states under the same input condition) in the system. The effects of incidence angle and metal layer thickness on bistability are systematically investigated. Results indicate that the incidence angle significantly affects the bistable threshold, whereas the metal layer thickness has minimal impact on the threshold but influences the displacement amplitude. The proposed structure provides a tunable bistable system with potential applications in all-optical switching, high-sensitivity biosensing, and photonic integrated circuits.