Effects of Size and Oxidation on the Nonlinear Optical Response and Optical Limiting of Graphene Oxide Sheets

In the present work we report on the effect of the size and the degree of oxidation on the third-order nonlinear optical response and the optical limiting action of water dispersed graphene oxide (GO) sheets, under 4 ns and 532 and 1064 nm laser excitation. The results show clearly that both the nonlinear optical (NLO) third-order susceptibility chi((3)) and the optical limiting (OL) threshold depend importantly on the size of the GOs, scaling linearly with the lateral size. In addition, it was found that the similar size but highly oxidized GO samples exhibited lower NLO response than the less oxidized ones, while their OL efficiency was found to be slightly affected by the degree of oxidation, increasing with the increase of the size of the GO sheets. The OL thresholds of the graphene oxide samples were found to be very low, comparable to some of the benchmark optical limiting materials. The observed size dependent NLO response of the GOs seems to be closely connected to the size of the conjugated areas of the graphenic sheets. The findings suggest a straightforward and efficient way for preparing graphene oxide sheets exhibiting custom-made nonlinear optical properties for specific applications in optoelectronics and photonics.