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

Abstract

Using 800 nm infrared, 150 femtosecond (fs), 80 MHz high repetition rate laser pulse excitation, intensity-dependent (I o = 245-735 MW/cm 2) 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 (I o = 245 MW/cm 2). 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 CuFe 2 O 4-(40 wt%) rGO at 735 MW/cm 2 excitation, which is attributed to the combined contribution of rGO and CuFe 2 O 4 that is four times higher than pure rGO and CuFe 2 O 4. The presence of layer like CuFe 2 O 4 nanoplatelets upon the layer-structured rGO offers an added advantage in enhancing the nonlinear absorption coefficient. Near-resonant ESA-based optical limiters comprising CuFe 2 O 4-rGO can possibly be used as a versatile optical limiting material for eye safety against intense, high repetition rate fs laser pulses.