| The traditional dyes have been growing rapidly as "functional dyes" because of their special properties of optics,electronics and magnetism in the field of high-tech.In the known "functional dyes",phthalocyanines have attracted a great deal of attentions due to their unique physical and chemical properties.Among them,the metal-phthalocyanine,as a very promising organic nonlinear optical material,has particularly aroused strong research interest.In this dissertation,experimental and theoretical studies on the nonlinear absorption properties and optical limiting properties of metal-phthalocyanine are performed mainly by the sensitive single-beam z-scan technique using the femtosecond laser.The main contents,research conclusions and innovations are summarized as following:(1) The z-scan technique used for the measurement of nonlinear optical properties is presented.The principle and theoretical calculation process of z-scan technique are analyzed in detail,and the influence factors in the z-scan measurement are disscused, which provide a theoretical basis and instruction for the experimental researches in the dissertation.(2) The electronic structures and electronic spectra of two metal-phthalocyanines are studied by quantum chemical caculation.Using the Hyperchem software,the geometrical molecular structures of cobalt phthalocyanine and copper phthalocyanine are firstly optimized by the semi-empirical PM3 method and the electronic spectra are then calculated by the ZINDO/S method,and the relationship between the visible absorption maximum(λmax) and the molecular structure of phthalocyanines with odd total electron numbers is concluded qualitatively.The results show that the calculated electronic spectra based on the optimized geometrical molecular structures are well consistent with the experimental values.OWFπ-π(π-πoverlap weighting factor,which is considered as a measurement of the extent ofπ-electron delocalization) andλmax is in well linear relationship.The study of seeking the relationship between the molecular structures and their optical properties provides a theoretical instruction for synthesizing new nonlinear optical materials.(3) The experimental and theoretical studies on the nonlinear absorption(NLA) properties and optical limiting properties of metal-phthalocyanine solutions are performed. Using the femtosecond seed laser,the NLA properties of copper phthalocyanine solutions are studied by the sensitive single-beam z-scan technique.The relationship between the input laser power and NLA properties,and the relationship between the solution concentration and NLA properties are discussed in detail.The results show that the copper phthalocyanine solutions exhibit reverse saturable absorption(RSA) effect,which mainly originates from three-photon absorption(3PA);and the RSA effect becomes stronger with the input laser power increasing when the sample solution concentration is low,while for the high concentration sample solution,with the input laser power increasing,the RSA effect first becomes stronger,then becomes saturable,and finally becomes weaker due to the "optical fading" phenomenon.In addition,the optical limiting performances for 1064 nm continual-wave laser of copper phthalocyanine and polychloro copper phthalocyanine solutions have been investigated.The results of the steady-state rate equation analysis show that the good optical limiting performances are mainly attributed to RSA induced by the absorption of triplet excited state.(4) The experimental and theoretical studies on the NLA properties and optical limiting properties of metal-phthalocyanine thin film are performed.Using femtosecond regenerative amplifier laser,the NLA properties and optical limiting properties of copper phthalocyanine thin film are investigated by the sensitive single-beam z-scan technique.In the open-aperture(OA) z-scan measurements of the film,a transition from saturable absorption(SA) to RSA is observed as the excitation intensity is increased.An efficient four-energy-level model for the organic materials excited by femtosecond pulse laser is developed,and based on which the dynamic rate equation analysis is performed and the intensity dependence of level populations is obtained,which reveals the source of NLA. The results show that the transition from SA to RSA is ascribed to the fifth-order effect of excited-state absorption(ESA) induced by two-photon absorption(TPA) process when the input laser intensity reaches a critical value.Furthermore,it is found that the copper phthalocyanine thin film possesses a large fifth-order absorption coefficientβ5 (0.24×10-21cm3/W2).It indicates that the copper phthalocyanine thin film could be a very promising candidate for optical limiting material.
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