Nonlinear optical characteristics of monolayer MoSe2

In this study, we utilized picosecond pulses from an Nd:YAG laser to investigate the nonlinear optical characteristics of monolayer MoSe2. Two-step growth involving the selenization of pulsed-laser-deposited MoO3 film was employed to yield the MoSe2 monolayer on a SiO2/Si substrate. Raman scattering, photoluminescence (PL) spectroscopy, and atomic force microscopy verified the high optical quality of the monolayer. The second-order susceptibility.(2) was calculated to be similar to 50 pm V-1 at the second harmonic wavelength lambda(SHG)similar to 810 nm, which is near the optical gap of the monolayer. Interestingly, our wavelength-dependent second harmonic scan can identify the bound excitonic states including negatively charged excitons much more efficiently, compared with the PL method at room temperature. Additionally, the MoSe2 monolayer exhibits a strong laser-induced damage threshold similar to 16 GW cm(-2) under picosecond-pulse excitation. Our findings suggest that monolayer MoSe2 can be considered as a promising candidate for high-power, thin-film-based nonlinear optical devices and applications.