Wide-Bandgap 2D SnS2-Based All-Optical Photonic Devices with Strong Nonlinear Optical Response due to Spatial Self-Phase Modulation

Tin(IV) sulfide (SnS2) is a widely used material for constructing photonic diodes due to its high bandgap (∼2.6 eV), strong dielectric response, and reverse saturable absorption (RSA). However, the nonlinear optical (NLO) responses of SnS2, including n2 and χ(3), have largely been largely unexplored. This study synthesizes two-dimensional (2D) nanoflakes (NFs) of SnS2 using a cost-effective hydrothermal method and investigates its NLO responses through spatial self-phase modulation (SSPM). Varying concentrations and optical path lengths were employed to elucidate the phenomena, and the Wind Chime model for SSPM was studied by using different solvents. Calculations reveal high NLO properties (n2: 2.53 × 10–5 cm2/W, χtotal(3): 7.24 × 10–3 esu), indicating SnS2's superior NLO characteristics compared to most other two-dimensional layered materials (2DLMs). All-optical diodes were constructed by using SnS2 and other 2DLMs (Bi2Se3, CuPC, and graphene) for potential applications in photonic devices. This work sheds light on SnS2's exceptional NLO properties and its potential in advanced photonic technologies.