Ultrafast third order nonlinear optical properties of self-assembled indium phthalocyanine multilayer films

Abstract An ultrathin composite films with alternated layers containing anionic lithium tetracarboxyl indium phthalocyanine chloride (ClInPc(COOLi)4) and cationic poly(diallydimethyl ammonium chloride) (PDDA) were prepared using layer-by-layer assembly technique. The resulting films were characterized by Ultraviolet-visible and Fourier transform infrared spectroscopy, showing regularly consecutive adsorption. The ultrafast third-order nonlinear optical properties of the films were investigated via a 4f coherent imaging system with phase object with 190 fs laser pulses at 532nm. The results demonstrate that the ultrathin films exhibited excellent self-focusing effect (n2 ∼ 8.86 × 10−17 m2/W) and reverse saturable absorption properties (β ∼ 5.19 × 10−10 m/W), while the nonlinear optical response of the same composite in aqueous solution were found to be negligible. Our results indicate that the ClInPc(COOLi)4/PDDA film is a promising candidate for future nonlinear optical devices.