Third-order Optical Nonlinearities Of PPV Derivatives And Metalloorganic Compounds

On the basis of the summarization and review on the researches and developments of the third-order optical nonlinear materials, the third-order optical nonlinearities of poly(l,4-phenylene vinylene) (PPV) derivatives and metalloorganic compounds as well as the optical switching effects of poly(l,4-phenylene vinylene) (PPV) derivatives are investigated.In the first part, the requirements for the third-order nonlinear optical materials in the field of optical signal processing are discussed, the quantum-chemical evaluation of molecular polarizabilities are reviewed. The major experimental techniques used to probe the third-order nonlinearities, the researches and developments of the third-order nonlinear optical materials as well as the nonlinear waveguide photonic devices are systematically summarized.In the second part, a series of new polymer thin films, including poly(l,4-phenylene vinylene) (PPV), poly(2-bromo-l,4-phenylene vinylene) (BrPPV), poly(2-chloro-1,4-phenylene vinylene) (C1PPV), poly(2,5-dibromo-l,4-phenylene vinylene) (Br2PPV) and poly(2,5-dichloro-l,4-phenylene vinylene) (C12PPV), with high environmental and thermal stability, high optical damage threshold, and good film quality, are successfully prepared by the "precursor-route" method. Their third-order optical nonlinearities and time responses are measured by picosecond forward three-dimensional degenerate four-wave mixing technique. In the near resonance region (532nm), the measured third-order nonlinear optical coefficients are approximately 10" ~ W檈su, and their time response are estimated to be less than picosecond. The Kerr effect, which arise from the distortion of the large quasi-one-dimensional 7t-conjugated electronic charge distribution at the backbone in PPV derivatives, is main reason for generating third-order optical nonlinearities, and their optical nonlinearities are near-resonantly enhanced to a certain extent. The experimental results of UV-visibleabsorption spectra, fluorescence spectra and diffuse reflectance furrier transform infrared spectra reflect that there is a significant contribution to rc-electron density from the subsitutents at the phenylene ring in PPV derivatives, and thus their x(3) values decrease with a decrease in rc-electron density at the backbone. Moreover, the optical switching effects are investigated by pump-probe method, and the optical switching responses of PPV, BrPPV, CIPPV, Br2PPV and C12PPV thin films are measured to be approximately 24ps.In the third part, the third-order optical nonlinearities for lanthanum(III) complexes with 1,10-phenanthroline components, such as 1,10-phenanthroline, [bis( 1,10-phenanthroline)lanthanum(III)] nitrate and [nitrato-fluoracil-bis( 1,10-phenanthroline)lanthanum(III)] nitrate, are firstly measured by Z-Scan technique. The third-order nonlinear optical susceptibilities increase in turn from 1,10-phenanthroline to [bis(l,10-phenanthroline)lanthanum(III)] nitrate to [nitrato-fluoracil-bis(l,10-phenanthroline)lanthanum(III)] nitrate. As rare earth metal ion La3+ coordinated with 1,10-phenanthroline, one-photon and two-photon excited UV fluorescence spectrum peaks are slightly moved to longer wavelength region, which reflects that two 1,10-phenanthrolines may be coupled each other by Lanthanum(III), and thus the x(3) values increase. Besides, the optical nonlinear refractive index n? and its time response spectrum of copper phthalocyanine thin film deposited on a glass or quartz substrate by the vacuum deposition method are firstly investigated by time-resolved Z-scan technique. The measured x(3) a"d response time are -1.3 x 10"8esu and ~ lOOps, respectively. Its optical nonlinearities, which mainly arise from the distortion of the two-dimensional ji-conjugated electronic system of phthalocyanine ring, can be enhanced due to incorporation of copper(II).In the last part, the main results in this dissertation are summarized, and the possible future developments are discussed.