Research on graphene has opened up a door to a novel two-dimensional (2D) nano-system. Layered transition metal sulfides (such as MoS₂, MoSe₂, MoTe₂, WS₂), one of the typical graphene analogues, have been paid great attention due to theirunique optical properties in comparison with their bulk form. However, their ultrafast nonlinear optical properties and the corresponding ultrafast photonic devices research have been rarely reported.

Recently, Prof. Jun Wang at Shanghai Institute of Optics and Fine Mechanicsand his collaborators, have for the first time reportedthe ultrafast saturable absorption performance in 2D layered MoS₂ nano-materials in the near infrared wavelength band.Related research has been published in "American Chemical Society - Nano"[ACS Nano, 7 (10), 9260-9267 (2013)].

The research team has successfully prepared 2D MoS₂ dispersions with high-quality layered nanosheets using liquid-phase exfoliation technology. Ultrafast nonlinear optical experiments showed that MoS₂ nanosheets have more excellent thangraphene saturable absorption performance for the femtosecond pulses innear-infrared laser pulses.

The exciting results have implied a huge potential of the layered MoS₂ represented 2D transition metal sulfides in the development of nanophotonic devices, such as mode-lockers, laser protection optical limiter and optical switches.