▎ 摘　　要

Herein, a simple, low-cost, and scalable process is developed to prepare the reduced graphene oxide (rGO) thin films (TFs) with strong optical nonlinearity. To do so, a chemical reduction method (using inorganic agent hydroiodic acid) and drop-casting technique are used. Optical nonlinearity of the prepared thin rGO film is measured by the Z-scan technique at low light intensity (continuous-wave wavelength of 632 nm). The result of optical nonlinearity responses is illustrated by a remarkable nonlinear refraction index (n(2) approximate to 10(-4) cm(2) W-1) as well as a considerable nonlinear absorption coefficient (beta = 1.43 x 10(-8) cm(2) W-1) compared with similar reported results. Moreover, experimental results show that the prepared film enjoys a positive nonlinear refractive index with strong optical nonlinearity. Results also confirm that the changes made in optical absorption of rGO TFs are due to state filling effects and the optical nonlinearity proportional to the carriers' density is in fact due to thermal effects of SiO2 substrate.