Fifth-order optical nonlinear response of semiconducting 2D LTMD MoS2

The effective fifth-order susceptibility, , of two-dimensional (2D) semiconducting layered transition metal dichalcogenide (LTMD) molybdenum disulfide ( ) is reported here for the first time, to the best of our knowledge. Using the -scan technique with a laser operating at 800 nm, 1 kHz, 100 fs, we investigated the nonlinear behavior of suspended in acetonitrile (concentration, 70 µg/ml). The effective nonlinear refractive index , proportional to , was measured for monolayer nanoflakes, prepared by a modified redox exfoliation method. We also determined the value of the nonlinear refractive index , which is related to the material’s effective third-order optical susceptibility real part, . For comparison, we also investigated the nonlinear response of tungsten disulfide ( ) monolayers, prepared by the same method and suspended in acetonitrile (concentration, 40 µg/ml), which only exhibited the third-order nonlinear effect in the same intensity range, up to . Nonlinear absorption was not observed in either or .