Optical Nonlinearity Of Metal (Mo/W) Nest Phase Clusters And Zn Porphyrin Cluster

Nonlinear optical limiter can be used to protect photosensitive devices and eyes from damage of laser. Research on nonlinear optical materials and optical limiting effect is one of hot fields of photoelectric information functional materials. Recently, inorganic transition metal cluster compounds are very attractive for their strong optical nonlinearity, good optical limiting properties, variability of molecular structure and skeletal atom. In this thesis, properties of optical nonlinearity and optical limiting effect in the inorganic metal cluster with a nest structure are investigated. The main works include as follows.Nonlinear refraction of the inorganic metal clusters [MOS₃Cu₃(4-pic)₆]·ClO₄ (M=W, Mo) with a nest structure and different skeletal metal atoms are studied under different intensity of laser utilizing the Z scan technique. The experimental results and the theoretical analysis prove that these inorganic metal clusters have a fifth-order optical nonlinearity. As we known, this is the first time to report the fifth-order optical nonlinearity in the inorganic metal cluster.Optical limiting properties in the inorganic metal cluster [WOS₃Cu₃I(4-pic)₆] with nest structure are measured at the wavelength of 532 nm and 630 nm with tunable laser pulses, and the experimental result is compared with the optical limiting standard material C60 dissolved in toluene. At 532 nm, the optical limiting performance in this metal cluster is better than that in the C60, but at 630 nm, the property of the optical limiting in the C60 is better than that in the metal cluster. Besides, the optical limiting performance in the metal cluster at 532 nm is better than that at 630 nm.The mechanism of the optical limiting in the solvent samples of the metal cluster [WOS₃Cu₃I(4-pic)₆] is explored with a pump-probe technique in red- wavelength and green-wavelength. As compared, the pump-probe experiments of C60 and carbon black suspensions are also performed. It is found that the main mechanism of the optical limiting in the sample studied is excited-state absorption at 532 nm and 630 nm, which is consistent with C60. The experimental results are analyzed theoretically with the excited-state absorption. Results prove that the mechanism of optical limiting of the metal cluster is the excited-state absorption of the single state under ps laser, and the mechanism of optical limiting of the metal cluster is the excited-state absorption of the triple state under ns laser.It has been reported that a similar properties of the optical limiting for the transition metal clusters in different solvent. However, it is found with our experiments that the optical limiting properties are relevant to the solvents, such as acetonitrile anhydrous, chloroform and methylene chloride, for the inorganic metal compounds [MOS₃Cu₃I(4-pic)₆](M=W,Mo) with a nest structure, which result for the change of the local electrical field and electronic configuration by solvent.The optical nonlinearity of the inorganic metal cluster [MoOS₃Cu₃I(4-pic)₆] with a nest structure relevant to solvent is studied experimentally. The coefficients of nonlinear refraction and nonlinear absorption in the metal cluster dissolved in different solvents are measured. It is found that the nonlinear absorption coefficients of the metal cluster dissolved are different when the solvent is different; the sign of the nonlinear refraction for the cluster dissolved in DMF is negative, but positive in acetonitrile and methylene dichloride. So the optical nonlinearity of the metal cluster is relevant to the solvent.The excited-state absorption induced transient thermal refraction is studied theoretically, the influence of the excited-state absorption induced transient thermal refaction to the optical nonlinearity is measured experimentally. In different condition, the competition between the excited-state absorption induced transient thermal refaction and the excited refraction cause large change of nonlinear refraction.