5,860 research outputs found
High-Q bismuth silicate nonlinear glass microsphere resonators
No full textThe fabrication and characterization of a bismuth-silicate glass microsphere resonator has been demonstrated. At wavelengths near 1550 nm, high-modes can be efficiently excited in a 179 µm diameter bismuth-silicate glass microsphere via evanescent coupling using a tapered silica fiber with a waist diameter of circa 2 µm. Resonances with Q-factors as high as were observed. The dependence of the spectral response on variations in the input power level was studied in detail to gain an insight into power-dependent thermal resonance shifts. Because of their high nonlinearity and high- factors, bismuth-silicate glass microspheres offer the potential for robustly assembled fully integrated all-optical switching devices
Towards improvement of bismuth and tellurium as a thermoelectric material for energy harvesting through nanostructuring
No full textIt has been demonstrated that lyotropic liquid crystal templates (LLCT) with mesoporous structures can be used during electrodeposition of thin films to produce films with a mesoporous structure transferred from the LLCT. Here we report the electrodeposition of mesoporous bismuth telluride (Bi2Te3) films from hexagonal structured LLCTs formed from mixtures of Brij®C10 and electrolyte solution in ratios of (55:45, 50:50, 45:55). The introduction of a mesoporous nanostructure to the bismuth telluride films should improve the thermoelectric properties of the material. Optimisation of the electrolyte solutions has been carried out, studying the effects of using the metals bismuth (Bi) and tellurium (Te) and the metal salts bismuth citrate (C6H5BiO7), bismuth nitrate pentahydrate (Bi(NO3)3·5H2O and tellurium dioxide (TeO2) dissolved in nitric acid (HNO3) or citric acid (C6H8O7) in different ratios and concentrations. The addition of a buffer solution made of citric acid and sodium citrate (C6H5Na3O7) has also been investigated. The lyotropic liquid crystal phases present for mixtures containing different concentrations of Brij®C10 and these electrolyte solutions has been looked at, including the production of phase diagrams. The liquid crystal template mixtures have been characterised using a polarised optical microscope (POM) and wide and small angle X-ray Diffraction (XRD) and Cyclic Voltammetry (CV). The deposited thin films have been characterised using wide and small angle XRD, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX), confirming that hexagonally nanostructured thin films in the (110) orientation with a composition close to Bi2Te3 have been produced
Extruded small-core bismuth oxide glass holey fibres
No full textWe report our progress on the fabrication and characterisation of highly nonlinear bismuth oxide glass holey fibres. The measured losses for these fibres were ~3 dB/m at 1.55 µm, and the effective nonlinearity of the smallest core fibre was as high as 1100 W at the same wavelength
Development of bismuth doped silica fibres for high power sources & long wavelength generation from ytterbium doped fibre lasers
No full textA detailed study of fabrication and characterisation of bismuth (Bi) doped silica optical fibre has been investigated. Three different fibre fabrication techniques were applied to study the possible influence on Bi-luminescence: modified chemical vapour deposition (MCVD) and the solution doping technique, MCVD chemical-in-crucible deposition technique and the powder-in-tube (PIT) technique. Spectroscopic absorption and Bi luminescence and fluorescence decay properties under different pumping wavelengths and with different host glass compositions are presented and provide important information for device applications. The influence of unsaturable loss on laser performance is investigated. The feasibility of direct laser diode pumping of Bi-doped fibre lasers at the wavelengths of 915 and 975 nm was examined by measuring excited state absorption in Bi-doped silicate fibres for the wavelength range of 900 -1300 nm. Enhancement in spectroscopic properties of Bi-doped fibre, by H2-loading, has been examined.Bi-doped fibre laser operating in the wavelength region of 1160-1179 nm has been demonstrated. The fibre laser performance at 1179 nm was investigated incorporating different cooling arrangements. The operation of Bi-doped fibre amplifier at 1179 nm, in both low and high input signal regime, was also examined. An all-fibre, narrow-linewidth, high power Yb-doped silica fibre laser at 1179 nm has been demonstrated. Furthermore, theoretical work confirms that the proposed laser architecture can be easily scaled to higher power
Homogenous Bismuth LMCT Photocatalysis
No full textLigand-to-metal charge transfer (LMCT) photocatalysis allows the activation and synthetic utilization of halides and other heteroatoms in metal complexes. The coordination makes photoinduced intramolecular electron transfer processes even at very short excited state lifetimes possible. A screening assay identifying LMCT activity enabled us to expand this catalysis concept to main group elements, such as bismuth. Bismuth (III) complexes generate the elusive bismuth (II) species and electrophilic carboxyl and chlorine radicals upon irradiation. The latter was utilized in C(sp3)–H bond activation and redox neutral trapping in a Giese-type coupling protocol. Combined cyclovoltammetry and UV-vis studies gave insight in the radical behavior of the highly reactive bismuth (II) catalyst fragment
Optical and electronic properties of bismuth-implanted glasses
No full textPhotoluminescence (PL) and excitation spectra of Bi melt doped oxide and chalcogenide glasses are very similar, indicating the same Bi center is present. When implanted with Bi, chalcogenide, phosphate and silica glass, and BaF2 crystal all display characteristically different PL spectra to when Bi is incorporated by melt-doping. This indicates that ion implantation is able to generate Bi centers which are not present in samples whose dopants are introduced during melting. Bi-related PL bands have been observed in glasses with very similar compositions to those in which carrier-type reversal has been observed, indicating that these phenomena are related to the same Bi centers, which we suggest are interstitial Bi2+ and Bi clusters
[Hepatic cystadenoma: a case report].
No full textHepatic cystadenoma is a rare tumor arising from the biliary system. Although ultrasound and CT scan show peculiar features, diagnosis is not easy preoperatively. Because of the unreliable natural history of cystadenoma, total excision of the neoplasm by hepatic resection seems to be the treatment of choice. A case of benign cystadenoma treated by minor liver resection is reported
Approccio palliativo alle ostruzioni della convergenza biliare principale secondarie a neoplasia epatica.
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