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

The effective fifth-order susceptibility, chi((5))(eff), of two-dimensional (2D) semiconducting layered transition metal dichalcogenide (LTMD) molybdenum disulfide (MoS 2 ) is reported here for the first time, to the best of our knowledge. Using the Z-scan technique with a laser operating at 800 mn, 1 kHz, 100 fs, we investigated the nonlinear behavior of MoS2 suspended in acetonitrile (concentration, 70 mu g/ml). The effective nonlinear refractive index n(4,) e(ff) = -(7.6 +/- 0.5) x 10(-26) cm(4)/W-2, proportional to Re chi((5))(eff), was measured for monolayer MoS2 nanoflakes, prepared by a modified redox exfoliation method. We also determined the value of the nonlinear refractive index n(2) = +(4.8 +/- 0.5) x 10(-16) cm(2)/W, which is related to the material's effective third-order optical susceptibility real part, Re chi((3))(eff). For comparison, we also investigated the nonlinear response of tungsten disulfide (WS2) monolayers, prepared by the same method and suspended in acetonitrile (concentration, 40 mu g/ml), which only exhibited the third-order nonlinear effect in the same intensity range, up to 120 GW/cm(2). Nonlinear absorption was not observed in either MoS2 or WS2. (C) 2021 Optical Society of America