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 Fth 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.