Visible light nonlinear absorption and optical limiting of ultrathin ZrSe₃ nanoflakes

The nonlinear absorption and nonlinear refractive properties of ZrSe₃ nanoflakes were studied with a 6.5 ns pulse laser at 532 nm. Open-aperture Z-scan curves reveal that ZrSe₃ nanoflakes have a strong reverse saturable absorption property, and close-aperture Z-scan curves show that ZrSe₃ dispersions possess a positive nonlinear refractive index caused by self-focusing. The nonlinear absorption coefficient, the nonlinear refraction coefficient, and the figures of merit (FOM) of ZrSe₃ dispersed in water with linear transmittances of 0.86 at input energy of 18 μJ are 6.35 × 10^-10 m W^-1 15.73 × 10^-17 m² W^-1, and 10.09 × 10^-11 esu · cm respectively. In addition, nonlinear optical (NLO) performance of ZrSe₃ nanoflakes depends on organic solvent dispersions. ZrSe₃ nanoflakes in water dispersions have the largest FOM of 10.27 × 10^-11 esu · cm, while the FOM in ethanol dispersions is 5.41 × 10^-11 esu · cm at the same input energy of 26.5 μJ. The optical limiting threshold F_th of ZrSe₃ nanosheet is 2.2 J cm^-2 under picosecond laser pulse. The Results imply that ZrSe₃ nanoflakes are an extraordinarily promising material for novel nanophotonic devices like optical limiters.