Femtosecond nonlinear absorption and optical limiting action in nanoplatelet CuFe2O4-decorated rGO nanocomposites

Using 800 nm infrared, 150 femtosecond (fs), 80 MHz high repetition rate laser pulse excitation, intensity-dependent (Io = 245–735 MW/cm2) measurements on the nonlinear absorption of copper ferrite hetero-architecture functionalized with three rGO contents (15, 25 and 40 wt%) were performed. Copper ferrite–rGO nanocomposite demonstrated a peculiar W-pattern [a peak (saturable absorption) with two valleys [reverse saturable absorption (RSA)] at extreme] in the open aperture Z-scan data for the decorated (15 wt%) rGO systems recorded at a low peak intensity (Io = 245 MW/cm2). The Z-scan traces were dominated by RSA characteristics due to two-photon absorption process at high peak intensities. The variation in intensity-dependent nonlinear absorption coefficient and ground-state absorption at laser excitation wavelength revealed the presence of excited-state absorption (ESA). The maximum two-photon absorption coefficient was recorded for CuFe2O4–(40 wt%) rGO at 735 MW/cm2 excitation, which is attributed to the combined contribution of rGO and CuFe2O4 that is four times higher than pure rGO and CuFe2O4. The presence of layer like CuFe2O4 nanoplatelets upon the layer-structured rGO offers an added advantage in enhancing the nonlinear absorption coefficient. Near-resonant ESA-based optical limiters comprising CuFe2O4–rGO can possibly be used as a versatile optical limiting material for eye safety against intense, high repetition rate fs laser pulses.