Synthesis Of Metal Silver/Copper Nanowires And Investigation Of Their Optical Nonlinear Properties

One dimensional metal nano-materials combine the properties of one-dimensional nano-structural materials and metals, and have important potential application prospect in such fields as optics, electronics, magnetics and so on. Successful preparation of one-dimensional metal nano-materials has great significance in realizing practical function-devices in nano-scale. Investigation on their optical nonlinearity and optical limiting effect can not only give us a deeper understanding of the interaction between laser and materials, as well as the origin of optical nonlinearity in metal nanowires, but also help us to find the factors which are associated with optical limiting capability, and then instruct us to design, optimize and synthesize ideal optical limiting materials.On the basis of fabrication of metal Ag and Cu nanowires separately with a novel solid-state ionic method, this paper lays emphasis on researches about the characteristics of optical limiting in Ag nanowires and optical nonlinearities in Ag and Cu nanowires. The main contents are as follows:Ag and Cu nanowires were fabricated by use of a solid-state ionic method. Morphologies, crystal structures and chemical components of the nanowires were analyzed and characterized by means of SEM, TEM, XRD and absorption spectrum.Based on effective permittivity theory and local field theory, the theory of permittivity effective media of the ellipsoida nano-particle dispersive system were derived and then applied to investigating the effective dielectric function correlated with the dispersive system of metal nanopartical and nanowires, and to calculating their third-order nonlinearity and nonlinear absorption coefficient. Also, the solvent effect of the metal nanoparticles and metal nanowires were discussed.The nonlinear refractive index (γ) of silver nanowires suspended in ethanol was measured by using Z-scan technique and laser radiation of various (nano-, pico-, and femto-second) pulse durations. Experimental results indicate silver nanowires have obvious positive refractive nonlinearities behaviors, pulse-width-dependent effect, and the nonlinear refractive index (γ) increases as the pulse duration increases from 110fs to 8ns. The pulse-width-dependent effect of silver nanowires and its origin were analyzed.Nonlinear absorbsion and refraction of silver nanowires suspended in de-ionized water and ethanol, respectively, were measured using Z-scan technique at 532nm wavelength. Experimental results indicate that the capability of nonlinear absorption and refraction of silver nanowires suspended in ethanol is better than that suspended in de-ionized water, which is due to the solvent dependence of the nonlinear behavior of the silver nanowires. The origin and the nonlinear solvent effect of the samples were analyzed by using theoretics derived. Optical nonlinearities of Cu nanowires suspended in de-ionized water induced by 8ns laser pulses from a frequency-doubled, Nd: YAG laser at 532 nm, were investigated using the Z-scan technique. And the origin of optical nonlinearities of Cu nanowires was discussed.The optical limiting of Ag nanowires suspended in de-ionized water was studied by using 30 picosecond laser pulses at 532nm with 2Hz repetition rate. The comparison for optical limiting of Ag nanowires induced by nanosecond pulse and by picosecond pulse was performed. It is found that the optical limiting of Ag nanowires induced by picosecond laser pulse is better than that induced by nanosecond one, which is arosed by the second scattering caused by the scattering center under different density of energy fluid.