For improving third-order optical nonlinear properties of metallophthalocyanine films

an thin composite film with alternating layers containing anionic tetra sulfonated phthalocyaninavanadium (VOTsPc) and cationic polyethylenimine (PEI) has been prepared by the electrostatic self-assembly technique.The alternating multilayer assemblies of VOTsPc/PEI were characterized by UV-Vis spectroscopy

showing the regularly consecutive adsorption process.Surface morphology of the fabricated VOTsPc/PEI thin film was studied by atomic force microscopy technique.The result showed that the film surface was smooth and homogeneous.The closely packed nanoparticles

with the average diameter of 75 nm and the mean interface roughness of 4.406 nm

can be easily seen on the film surface uniformly.By using a frequency-doubled Q switched Nd:YAG pulse laser system with ns/ps laser pulse

the third-order optical nonlinear properties of the film were studied by Z-scan measurements at wavelength of 532 nm with 4 ns pulses.By simulation and calculation of the experimental data

the nonlinear refractive index

n2 value and the nonlinear absorption coefficient

β value of a 30-bilayer VOTsPc/PEI film is 4.87×10-6 esu and 1.2×10-5 m/W

respectively.The third-order nonlinear susceptibility χ(3) value of the film is 1.57×10-6 esu by calculation.The VOTsPc/PEI film shows strong nonlinear reverse saturable absorption performance and has broad application prospects.