Nonlinear Optical Properties of Vertically-Aligned MoS₂ Nanosheets

This paper deals with the nonlinear optical (NLO) response of vertically-aligned MoS₂ (VA-MoS₂) nanosheets on a quartz substrate prepared by chemical vapor deposition (CVD). Scanning electron microscopy confirmed that VA-MoS₂ nanosheets were grown in specific experimental conditions. X-ray diffraction, Raman, and UV-Vis spectroscopies indicated the high-quality crystalline nature of the 2H-MoS₂ prototype with excitonic features. The NLO characterization of the VA-MoS₂ sample was performed by a Z-scan optical setup in the visible region (λ = 532 nm). Our VA-MoS₂ sample exhibited a highly unpredictable nonlinear refractive index (~ 10⁻⁵ cm² W⁻¹) and nonlinear absorption coefficient (~ 1 cm W⁻¹), suggesting its potential applications in nonlinear optical devices. It was shown that free-carrier nonlinearity may have contributed to the observed enhanced nonlinear optical properties.