Experimental observation of low threshold optical bistability in exfoliated graphene with low oxidation degree

•Exfoliated graphene flakes with low oxidation degree are prepared.•Nonlinearity enhancement for N-layer graphene dispersed inside a dielectric medium is shown.•Low threshold Optical Bistability is experimentally verified in exfoliated graphene.•The main contribution in Optical Bistability is discerned as the nonlinear dispersion.•It is shown that the enhanced nonlinearity can lead to instability, a route to chaos.

We have experimentally investigated low threshold Optical Bistability (OB) and multi-stability in exfoliated graphene ink with low oxidation degree. Theoretical predictions of N-layer problem and the resonator feedback problem show good agreement with the experimental observation. In contrary to the other graphene oxide samples, we have indicated that the absorbance does not restrict OB process. We have concluded from the experimental results and Nonlinear Schrödinger Equation (NLSE) that the nonlinear dispersion – rather than absorption – is the main nonlinear mechanism of OB. In addition to the enhanced nonlinearity, exfoliated graphene with low oxidation degree possesses semiconductors group III–V equivalent band gap energy, high charge carrier mobility and thus, ultra-fast optical response which makes it a unique optical material for application in all optical switching, especially in THz frequency range.