Experimental Study Of First Hyperpolarizability For N-confused Porphyrins Based On Hyper Rayleigh Scattering

The discovery of second harmonic，which is an important sign of the nonlinearoptics appearance in1960s. Since then, a series of valuable nonlinear opticalphenomena have been studied systematically and thoroughly, especially thesecond-order nonlinear optical phenomena of materials. Therefore, it is of greatsignificance to search for simple and effective methods to research the second-ordernonlinear optical properties of materials same as to measure the first hyperpolarizabilityof materials. Compared with the traditional Electric Field-Induced Second Harmonic(EFISH) method, the Hyper-Rayleigh scattering is a more excellent approach tocharacterize the second-order nonlinear optical properties of materials due to several ofmerits such as simpler to set up experimental system, widely measurement range andmore accuracy, etc. On the basis of the theory of the first hyperpolarizabilities, the mainpurpose of this thesis is to construct a Hyper-Rayleigh scattering experimental system,as well as research the second-order nonlinear optical properties of a series ofN-confused porphyrin(NCTPP) by the proposed system. The primary contents are asfollows:Based on the first hyperpolarizability theory, the dependences of the real part andimaginary part of linear polarizability on wavelengths are simulated numerically.Furthermore, the first hyperpolarizability as a function of the wavelengths of thefundamental light is explored. On the one hand, the effect of the damping in theresonance region on the convergence properties of the first hyperpolarizability isanalyzed deeply. On the other hand, we compare two kinds of numerical simulations tothe reported experimental results in terms of the first hyperpolarizability at thenon-resonant region. The results of the theoretical and experimental consistency showthat the theoretical model can be considered as an effective method to calculate orpredict the first hyperpolarizability of materials.According to the proposed theoretical model, the Hyper-Rayleigh scatteringexperiment system is set up successfully and its reasonableness and accuracy isvalidated correspondingly. The authenticity of the Hyper-Rayleigh scattering signal isproved from three aspects. The scattering intensity is measured and compared by theinterference filters with different central wavelengths. The pulses widths of thefundamental beam and scattering signal are measured, as well as both of pulse widthsare compared. As well as, the scattering intensity and the fundamental intensity areinvestigated. As an illustration, the proposed experimental system is used to measure thefirst hyperpolarizability of paranitroanilinum. Here, the measured value is in reasonable agreement with the reported one in the literature. As a result, this stable and reliableexperimental system can be viewed as an effective avenue to characterize thesecond-order nonlinear optical properties of other samples.Finally, the first hyperpolarizabilities of a series of N-Confused Porphyrins arestudied by the Hyper Rayleigh Scattering experimental system. The molecularstructures of the samples are analyzed by linear absorption spectrum. Also, In order toexclude the interference of fluorescence signal, the single-fluorescence spectrum andthe scattering spectrum of the samples are measured. In addition, the firsthyperpolarizabilities of samples are measured by the internal reference method, and theobtained experimental values are compared with the calculated theoretical ones by theab initio of quantum chemistry. Based on the experimental values and the scatteringspectra of samples, the first hyperpolarizabilities of samples in the case of differentwavelengths fundamental beam are estimated by the corrected dephasing and vibronicmodel.