Strong Nonlinear Response and All-Optical Applications in Hybrid Bismuth Halide with Spatial Self-Phase Modulation

Perovskite materials, known for their exceptional photoelectronic and photonic properties, have attracted considerable interest in the field of nonlinear optics (NLO). Herein, 0D organic–inorganic hybrid bismuth perovskite (PPA)₃BiI₆ (PPA = 3-phenyl-2-propen-1-ammonium) is successfully synthesized using the cooling-induced crystallization method. The nonlinear optical responses of this hybrid bismuth halide are investigated within the visible spectrum range of 405–532 nm by the spatial self-phase modulation (SSPM) method. It is found that (PPA)₃BiI₆ exhibits excellent third-order nonlinear susceptibilities (${\chi }_{\mathrm{monolayer}}^{(3)}$), up to 10⁻⁸ e.s.u. at 405 nm, which is larger than those of reported lead-free perovskites in previous research. The all-optical switching experiment is conducted, effectively realizing phase modulation of light through light interaction. Moreover, a novel unidirectional NLO excitation diode with a (PPA)₃BiI₆/SnS₂ hybrid structure is demonstrated for spatially nonreciprocal propagation. The research discovered a lead-free perovskite with superior nonlinear optical properties and systematically investigated its potential applications in photonic device technology.