Ultrafast and short-pulse excitation of nonlinear optical absorption in Graphene oxide and reduced Graphene oxide

Abstract

We investigate the effect of excitation laser pulsewidth (50 ns, 300 ps and 100 fs pulses) on the nonlinear absorption properties of graphene oxide (GO) and reduced graphene oxide (rGO) in the linear absorption band edge, using the excitation wavelength of 800 nm. GO is synthesized by the modified Hummers method, and rGO is obtained by hydrothermal reduction. Reverse Saturable Absorption (RSA) prevails for all excitation pulsewidths in GO, whereas in rGO RSA is prominent in the ns and fs regimes while Saturable Absorption (SA) dominates the ps regime. Due to its increased crystallinity and extended π conjugation, rGO exhibits excellent optical limiting for ns and fs excitations in comparison to GO.