Measurement of optical nonlinear refractive index response of graphene nanoparticles dispersed in an aqueous solution by Z scan technique

In this paper, colloidal suspension of graphene oxide nanoparticles (GONPs) were synthesized using the novel microwave assisted hydrothermal method. Different concentrations in distiller water is reported. Nonlinear optical properties of the samples were measured by the z-scan technique. For the experimental, a diode laser was used as an excitation source, the excitation beam was focused to a small spot by using a lens. Then, the sample was moved across the focal region along the z-axis. It was shown that the concentration of GONPs can greatly improve the nonlinear optical properties of the sample. The morphology and structure of GONPs, were evaluated by transmission electron microscopy (TEM), UV–Vis spectroscopy and Fourier Transform infrared spectroscopy (FTIR), respectively. From the experimental results, the optical nonlinear refractive indices of GONPs were obtained, ranging from −2.53 × 10⁻⁹ cm²/W to −2.57 × 10⁻⁹ cm²/W. This suggests that GONPs aqueous solution, could be a very promising nonlinear medium, establishing the bases of nonlinear photonics.