Third-order nonlinearities and optical limiting properties of complex Co2L3

With nanosecond pulses at a wavelength of 532 nm, we investigated the third-order optical nonlinearities of a dinuclear Co(II) triple-helical complex Co2L3 {L = bis[4-(2-pyridyl-methyleneamino) phenyl] methane} by a Z-scan technique. The optical limiting properties are measured by a transmission technique. The experimental data are theoretically fitted; the mechanism for the optical nonlinearities and the optical limiting properties is discussed. The absorption cross-sections of the ground state and the excited states are evaluated by a rate equation model.