Nonlinear saturable absorption of vertically stood WS_2 nanoplates

We report the nonlinear optical (NLO) properties of vertically stood WS2 nanoplates excited by 532-nm picosecond laser light. The nanoplates were synthesized by a no-catalyst thermal evaporation process. Raman spectroscopy and x-ray diffraction pattern indicate that the nanoplates are of high crystal quality. The nanoplates exhibit large nonlinear saturable absorption but negligible nonlinear refraction. Mechanisms of the NLO response are proposed.