Graphitic carbon nitride, a saturable absorber material for the visible waveband

For the first time to our knowledge, graphitic carbon nitride(g-CN) nanosheets are found to be an excellent saturable absorber material in the visible waveband. g-CNexhibits much stronger saturable absorption in this region than in the near-infrared region, unlike other two-dimensional materials such as graphene and black phosphorus. By the Z-scan method, the nonlinear absorption coefficient β of the material is first measured at three visible wavelengths, and for g-CNit is -2.05,-0.34, and -0.11 cm · GWat 355, 532, and 650 nm,respectively. These are much larger than -0.06 cm · GWat 1064 nm.