Tunable Enhanced Spatial Self‐Phase Modulation Effect in Silver‐Modified Black Phosphorus

Abstract Layered black phosphorus (BP) holds significant promise for nonlinear optics due to its in‐plane anisotropy and ultrafast carrier dynamic response. Despite its impressive third‐order nonlinear optical properties (χ⁽³⁾ ≈ 10⁻⁸ e.s.u.), BP's practical application in optical communications faces challenges due to its flexibility limitations. In this study, Ag‐modified BP nanocomposites (BP‐Ag) are synthesized, and investigated their spatial self‐phase modulation (SSPM) properties in the visible range. The findings demonstrate that the SSPM effect of BP shows a significant enhancement with Ag modification, and the effect can be tuned by the Ag doping contents. Under 671 nm laser excitation, the third‐order nonlinear susceptibility χ⁽³⁾ of BP‐Ag increased to 2.62 × 10⁻⁸ e.s.u., a 67% improvement over pure BP (χ⁽³⁾ ≈ 1.57 × 10⁻⁸ e.s.u.). Additionally, the SSPM response time is reduced from 0.32 s (for BP) to 0.17 s (for BP‐Ag). This enhancement is attributed to the surface plasmon resonance effect in the BP‐Ag composite, as well as to the strengthened light‐matter interaction resulting from Ag hybrid energy levels. This work paves an avenue for the application of BP in tunable nonlinear optical devices.