Research On The Fabrication Of Nanoparticles Embedded Bismuthate Glass And Third-order Optical Nonlinear Characteristics

Bismuthate glasses as a novel species of heavy metal oxide glass possess extraordinary optical properties. Ascompared to conventional silicate and borate glasses, bismuthate glasses have higher density, linear and nonlinearrefractive index and wider infrared transmission region, which considered to be one of the best candidate materialsfor all-optical switches. On the other hand, metal nanoparticles as important materials, exhibit surface plasmonicresonance (SPR) in certain spectral region, which can greatly enhance their linear and nonlinear optical properties.In this paper, we introduced metal nanoparitlces to the bismuthate glasses. The material preparation takesadvantage of the thermal reduction effect of bismuthate glass in order to obtain high quality bulk metalnanoparticles glass composites. And the micro-structure and optical properties of these materials have beensystematically studied. We designed and optimized the preparation method from such basic study. The ultimategoal of this paper is yielding the novel nano-metal glass composites that exhibit communication band coveredSPR. The main content of this thesis are as following:(1) Vitreous network formation and optical characteristics of glasses within Bi2O3-B2O3binary system. Inthis part, a series of Bi2O3-B2O3bismuthate glasses with different Bi/B ratio were prepared by melt-quenchmethod, and their density, refractive index, optical absorption and Raman spectra were measured. Accordingly,formation mechanism of the vitreous network of Bi2O3-B2O3binary glasses was investigated, and the oxygencompetition mechanism between B2O3and Bi2O3with different Bi/B ratio was demonstrated. Dependence ofglass composition upon their structural and optical properties was discussed, which gives a theoretical support andfeasible path to the realization of bismuthate glasses with ultrahigh optical performances.(2) Study on spectroscopy and third-order optical nonlinear characteristics of Ag-nanoparticles embeddedbismuthate glass. In this paat, Ag nanoparticles embedded bismuthate glass composite was prepared by using athermo-chemical reduction method. Surface plasmon resonance (SPR) absorption of the Ag nanoparticles wasobserved by utilizing UV-visible absorption spectra. The Raman spectra evidenced the evolution of the structuralunits of the glass after introduction of Ag nanoparticles. Z-scan and optical Kerr shutter technique withfemtosecond laser as excitation source was applied to investigate third-order optical nonlinearities of the nanocomposite in near-infrared region. The results show that the silver-bismuthate nanocomposite possesses Kerrresponse in scale of sub-picosecond, and its nonlinear refraction γ of was dramatically increased up to29timesunder the influences of hot electron effect and local field effect, while nonlinear absorption was suppressed due tothe bleaching effect of SPR at high incident laser intensity.(3) Improvement of third-order optical nonlinearity performance of bismuthateglasses by introducing silver nanoparticles. Silver nanoparticles (Ag-NPs) were prepared by incorporating silverions (Ag+) into bismuthate glasses through a consecutive melting–quenching–annealing process. The surfaceplasmon resonance behavior of the Ag-NPs showed a nonlinear dependence on the doping quantity of Ag+ions,and the optimum precipitation condition of the Ag-NPs was thus determined. Z-scan technique with femtosecondlaser as excitation source was applied to investigate third-order optical nonlinearities of the nanocomposite innear-infrared region. The nonlinear refraction γ of samples with optimum Ag-NP precipitation reached2.7×10-16m2/W, and two-photon absorption did not occur. Optical Kerr shutter technique revealed fast nonlinear responsetime (<1ps) of the nanocomposites.