Strong nonlinear optical refractive effect of self-assembled multilayer films containing tetrasulfonated iron phthalocyanine

Multilayer films containing anionic iron phthalocyanine tetrasulfonate (FePcTsNa4) and cationic poly(diallydimethyl ammonium chloride) were prepared using electrostatic self-assembled layer-by-layer technique. The growth of the film was monitored by ultraviolet–visible absorption spectroscopy, and the morphology of the film was characterized by atomic force microscopy. Polarized visible spectra showed that macrocycles of FePcTsNa4 in the film presented a flat orientation relative to the plane of the solid substrates. The third-order nonlinear optical properties of the film were studied by using Z-scan technique with laser duration of 21 ps at the wavelength of 532 nm. The FePcTsNa4/PDDA film exhibited strong self-focusing effect with n2 value of 4.13 × 10−15 m2/W, which is 4 orders larger than that of FePcTsNa4 aqueous solution.