Nonlinear optical absorption of SnX2 (X = S, Se) semiconductor nanosheets

Tin-based dichalcogenides such as SnS2 and SnSe2 have attracted wide attention due to their significant potential for the next-generation optoelectronic and photonic devices in nanotechnology. We investigate the nonlinear absorption of SnS2 and SnSe2 nanosheets using the Z-scan technique with nanosecond pulse and picosecond pulse at 532 nm for the first time. Z-scan measurement reveals that SnS2 nanosheets dispersions exhibit reverse saturable absorption (RSA) behavior under different pulses, which is in contrast to the saturable absorption (SA) observed in the SnSe2 nanosheets dispersions resulted from different band gaps. The nonlinear absorption coefficient (b) and the figures of merit (FOM) of SnS2 dispersed in ethanol with linear transmittances of 0.75 at input energy of 6.16 mu J in the nanosecond regime are 12.78 x 10(-10) m/W and 8.71 x 10(-11) esu.cm, respectively. As for SnSe2 nanosheet dispersions, b and FOM are -12.58 x 10(-10) m/W and 11.98 x 10(-11) esu.cm at the same input energy, respectively. The RSA behavior coupled to the smaller optical limiting threshold F-th (0.23 J/cm(2)) proves SnS2 a promising 2D material for protecting sensitive optical components or eyes from laser-induced damage. The SA performance indicates SnSe2 nanosheets prospective candidates for high-performance nanoscale nanophotonic devices like optical switches. (C) 2017 Elsevier B.V. All rights reserved.