Experimental Comparison of Nonlinear Optical Properties Between Graphene Oxide and Reduced Graphene Oxide

We delineate a comparative investigation between dispersed graphene oxide (GO) and reduced graphene oxide (RGO) by experimentally measuring their principal/nonlinear optical parameters. We show that the nonlinear refractive index of RGO is larger than that of GO while the nonlinear absorption coefficient of RGO is almost negligible. We particularly organize an experimental plan using GO and RGO inks included in a Mach-Zehnder interferometer and illuminated by a light beam with the wavelength 650 nm. We obtain that the lower threshold input power and more pronounced hysteresis loops are obtained for RGO in comparison to GO. We infer that the contribution of nonlinearity is majorly refractive in RGO rather than absorptive. In return, GO shows a larger absorptive nonlinearity compared to RGO in consequence of the larger nonlinear absorption coefficient. Although GO seems to be appropriate for the saturable absorption-based applications, we deduce that partially reduced GO is more preferred since it can appear as an active electrode providing then an ultrathin electric double layer required for ultrashort pulse generation. Our results indicate that RGO is also suitable for the electro-optical applications like the modulation through which the Fermi energy is to be tuned with a low bias voltage. As well, we propose RGO for all-optical applications like the optical switching for which the highly nonlinear response is required.