Excited State Absorption Dynamics In Metal Cluster Polymer [Cu₃IWS₄(4-bpy)₃]n Solution

Materials that possess nonlinear optical (NLO) properties have been investigated extensively for their potential applications in optical switches, optical limiting devices, and so on. Recently, metal clusters polymer have received much attention and been demonstrated to be a new kind of excellent NLO molecule. Such metal clusters polymer can have various kinds of architectures, which may change or enhance the optical nonlinearities and thus can be optimized for each photonic application. As a new kind of photoelectronical material, metal clusters polymer has attracted much attention of a great number of researchers. The research on the optical nonlinearity and optical limiting properties of clusters metal clusters polymer flourishes all over the world.In this dissertation, nonlinear absorptive property of a novel metal cluster [Cu3IWS4(4-bpy)3]n in DMF solution is studied by using an open-aperture Z-scan technique with picosecond and nanosecond laser pulses at the wavelength of 532nm.The experimental results show that the cluster has strong nonlinear absorption under the 8ns pulse excitation, and relatively weak nonlinear absorptive property under the picosecond pulse excitation. To gain an insight into the nonlinear origin of the cluster, a picosecond time resolved pump-probe experiments have been performed at 532nm on the metal cluster [Cu3IWS4(4-bpy) 3]n. The picosecond pump-probe response of the metal cluster is similar to that of C60 solution, which implies that the nonlinear mechanisms are the same of the two materials.The nonlinear mechanisms of metal cluster can be explained by using the five-level energy model. The experimental data are theoretically simulated; several optical-physics parameters of the cluster, especially the lifetime of higher excited singlet state of the cluster are obtained. The nanosecond nonlinear absorption can be attributed mostly to triplet-triplet state absorption, while the picosecond absorption data is almost completely attributable to the excited singlet state absorption. The ratio of the absorption cross-section of the excited-states to that of the ground state for the picosecond pulse is smaller than the ratio for the nanosecond pulse. So the cluster has strong nonlinear absorption under the nanosecond pulse excitation. Under the picosecond pulse excitation, the cluster exhibits a relatively weak nonlinear absorptive property.