Nonlinear optical response of graphene/silicon nanocomposites

In this experimental investigation, silicon nanoparticles and graphene nanosheets suspensions were produced by the pulsed laser ablation in distilled water separately. Then graphene and silicon were mixed in different volumetric ratio and irradiated by UV radiation to produced graphene/silicon nanocomposites. In order to characterize the structural and optical properties of samples, UV–Vis–NIR spectroscopy, Raman spectrum, and transmission electron microscopy were carried out. According to Raman spectra the defects introduced into the graphene nanosheets are more than the defects in the graphene/silicon nanocomposites. The extinction coefficients and bandgap energies of graphene/Si nanocomposites were decreased with increasing the amount of graphene suspension. The z-scan method was employed to estimate the role of the volume ratio of graphene nanosheets to silicon nanoparticles in changing the nonlinear responses of the graphene/silicon nanocomposites. Results of z-scan show that the nonlinear optical properties of graphene/silicon nanocomposites enhanced by increasing the concentration of Si nanoparticles. Furthermore, the measured values of third order nonlinear optical susceptibility, \(\chi^{\left( 3 \right)}\) of the graphene/silicon nanocomposites were from the order of 10⁻¹⁵ SI. Results show that the origin of optical nonlinearity of suspensions is due to the saturable absorption process.