Nonlinear Optical Properties And Raman Study OfCo(Ⅱ)-porphyrin And Fe(Ⅲ)-porphyrin

Porphyrin and its metallocompound not only have great importance to study of life science, but also have comprehensive applications to the field of technique. Meanwhile, the extensive interest of spectroscopists and academic chemists have been arosed by high symmetry (close to D4h) and particular elctronic structure of porphyrin. So, in our thesis, the nonlinear optical properties and Raman spectra of Co(Ⅱ)-porphyrin and Fe(Ⅲ)-porphyrin have been investigated.Nonlinear optics have been widely applied and profusely researched, in our article, its main phenomena and effects have been simply summarized. The investigation of nonlinear optics not only include the found of nonlinear phenomena and effects ,the study of its produce mechanism and rules ,the development of nonlinear optical new technique and the found of new material, but also include application of nonlinear optical effect and technique in every related field. The thermal self-defocusing effect and reverse saturable absorption properties of Co(Ⅱ)-porphyrin and Fe(Ⅲ)- porphyrin, two kinds of important compounds, have been testified. Moreover, The thermal self-defocusing effect and reverse saturable absorption properties can lead to optical limiting, so optical limiting device can be made. The thermal self-defocusing effect of Co(Ⅱ)-porphyrin has been measured by z-scan technique, the result of experiment show that the sample has reverse saturated absorption property under three laser waves.It's well known that both thermal self-defocusing effect and reverse saturable absorption can lead to optical limiting. Co(Ⅱ)-porphyrin has the optical limiting effect under those waves were found, and that the critical value of optical limiting reduces with the decrease of laser wave. Further more, the effect of optical limiting is very goodand the critical value is very low, so it's new optical limiting material with great potential application value. For Fe(Ⅲ)-porphyrin, the effect of solution concentration on optical limiting has been investigated, the experimental results indicate that the critical value of optical limiting reduces with the increase of concentration. The optical limiting properties to CW laser of them have been studied, as well as nonlinear properties under pulse laser have been studied by z-scan technique. Three curves of peak followed by valley using the single beam z-scan technique were got. According to M.Sheik－bahae's theory the sample has a negative nonlinear refractive index under 1064nm laser. Meanwhile, the minimum value of normalized transmittance of z-scan curves without diaphragm are found at the focus, and indicate that Co(Ⅱ)-porphyrin and Fe(Ⅲ)-porphyrin all have nonlinear absorption properties. Re of them have been calculated.Raman spectrum is about to molecular vibration and rotation , because Raman spectrum is involved in molecular structure, the information of molecular structure can be got by the investigation of molecular Raman spectrum.The intensity of Surface Enhance Raman Scattering is enhanced 104～107 than Normal Raman Scattering, because of its high sensitivity, SERS not only can detect the single molecule layer and submolecule layer adsorbed on metal surface, but also can provide the structure information of surface molecule, so SERS has been regarded as a good study technique of surface. In our article, the effect,theory of Raman spectrum and SERS technique have been briefly introducted. The Raman spectra of Co(Ⅱ)-porphyrin and Fe(Ⅲ)-porphyrin excited by 632.8nm and 457.5nm and SERS spectra using silver mirror as substrate have been measured. The main Raman peaks of spectra have been assigned. then the adsorption mode of Co(Ⅱ)-porphyrin and Fe(Ⅲ)-porphyrin in silver mirror substrate have been analyzed according to our assignment...