Near bandgap second-order nonlinear optical characteristics of MoS_2 monolayer transferred on transparent substrates

摘要

We have investigated the second-order nonlinear optical (NLO) properties of CVD-grown MoS_2 monolayer (ML) transferred onto transparent substrates such as fused silica and polyethylene ter-ephthalate. The physical properties of the transferred MLs were characterized by optical and NLO methods. We measured the second-order susceptibility χ~((2)) in the spectral range of λ = 1064-1600 nm in which the corresponding second harmonic radiation resonates with the exciton levels. It was found that χ~((2)) is strongly enhanced by up to a factor of 5 near the A- and B-exciton levels due to two-photon resonance. The absolute χ~((2)) values of our samples determined by both reflection and transmission geometry are on par with that of as-grown MLs. Our results imply that the cavity-confinement scheme can be employed for maximizing the nonlinear optical efficiency of atomically thin transition metal dichalcogenides for transparent/flexible optoelectronics applications, especially when oriented stacking of transferred MLs are controllable.