Nonlinear optical response of the SnS2 nanosheet-based multilayer film.

It is an effective strategy for enhancing the nonlinear optical response of materials to construct multilayer film structures. A periodic SnS₂/TiO₂ optical multilayer structure based on SnS₂ nanosheets and its nonlinear optical properties are measured by using an 800 nm femtosecond laser Z-scan technique. Experimental results indicate that the multilayer film exhibited saturable absorption and self-defocusing behavior. The equivalent nonlinear absorption coefficient (β_eff) and nonlinear refractive index (n₂) are enhanced toward -354.9 cm GW^-1 and -7.8 × 10^-3 cm² GW^-1, respectively, corresponding to 3.2 and 2 fold those of SiO₂:SnS₂ monolayer films with equivalent thickness. The enhancement is attributed to the synergistic effects of localized electric field increasement within the periodic SnS₂ layers and the band-edge shifting induced by refractive index modulation. The results demonstrate that the multilayer structure significantly enhances nonlinear optical performance of two-dimensional SnS₂, highlighting its potential for advanced photonic applications such as lasers.