Z-scan study of third-order nonlinear optical properties of three dmit complexes

Three dmit2− complexes, [(C4H9)4N]2[Mn(dmit)2], [(C4H9)4N]2[Cu(dmit)2] and [(C3H7)4N] [Ni(dmit)2], abbreviated as BuMn, BuCu and PrNi, were synthesized. Their third-order nonlinear optical properties in acetonitrile were investigated using the laser Z-scan technique with 20 ps pulses at 1064 nm. The Z-scan spectra revealed that BuMn exhibited self-focusing effect and negligible nonlinear absorption, BuCu exhibited self-defocusing effect and two-photon absorption, PrNi exhibited self-focusing effect and a stronger saturable absorption. The reason for the difference was analyzed. The nonlinear refractive index n2, the third-order nonlinear susceptibility □(3), the molecular second-order hyperpolarizability □ of these complexes were with the magnitude of 10−18 m2/W, 10−13 esu and 10−31 esu, respectively. All these results suggest that these materials are candidates for application in the different nonlinear optical fields at infrared band.