Nonlinear optical properties of spherical MoS2/TiO2 composite at visible wavelengths

Abstract Optical nonlinear absorption and refraction of spherical MoS 2 /TiO 2 nanocomposites were measured using Z-scan and spatial self-phase modulation (SSPM) at different wavelengths. The linear absorption spectra showed that MoS 2 /TiO 2 nanocomposite had obvious absorption at 500–700 nm, which was mainly attributed to the shape of MoS 2 and demonstrated by the finite-difference time-domain method. For nonlinear absorption, MoS 2 /TiO 2 composite showed enhanced two-photon absorption with high photon energy excitation (400 nm), and a tunable saturated single-photon absorption with low photon energy excitation (700 nm). For nonlinear refraction, it had no SSPM signal with short wavelength, but enhanced SSPM signal with long wavelength in visible band. These unconventional phenomena can be explained by the change of main absorber and the reversal of carriers transfer direction together.