2D layered nanomaterials, e.g., graphene and transition metal dichalcogenides (TMDCs), have been demonstrated to be potential candidates for photonic applications benefiting from their multifarious nonlinear optical (NLO) properties. All-optical modulation based on this NLO effect has been demonstrated in graphene integrated devices, which shows ultrashort response time and high modulation rate.

Therefore, it is quite significant to fully understand the NLO mechanism and investigate the optical modulation properties in these dispersions, which is the foundation to exploit optical modulators based on this kind of materials. However, few research has been reported on this aspect.

Recently, a collaborative study led by Dr. Jun Wang at Key Laboratory of Materials for High-Power Laser, ,Shanghai Institute of Optics and Fines Mechanics (SIOM) Chinese Academy of Sciences report the optically induced transparency and extinction in MoS₂, MoSe₂, and grapheme nanosheets in N-methyl-2-pyrrolidone (NMP). The 632.8 nm continuous-wave(cw) can be effectively modulated by 532 nm pulsed laser into signal light with peaks or valleys by tuning the excitation intensity using the pump–probe system. The Z-scan results reveal the coexisting and competition between SA and NLS effects in MoS₂ and MoSe₂ nanosheets dispersions, which are the main reasons for the optically induced transparency and extinction.

The finding was published in Adv. Optical Mater. 2017, 5, 1700543

They have demonstrated that the 632.8 nm cw probe light can be modulated to transparency and extinction induced by the combined interaction of SA and NLS responses in the MoS₂, MoSe₂, and graphene nanosheets dispersions under the 532 nm ns pump laser pulses. The large modulation depths under strong pump energies make these 2D nanomaterials potential candidates for optical modulators.

Figure . a) Schematic representation of the all-optical modulation process. b) Illustration of the SA and NLS mechanism in the nanosheet dispersion.