Bismuth Gallate Research Articles

Fluorescence and upconversion spectral studies of Ho 3+ in alkali bismuth gallate glasses

The absorption and emission spectra of Ho 3+ in alkali bismuth gallate glass matrices have been investigated in the visible and near-infrared. Strong fluorescence in the green ( λ∼549 nm), arising from the 5S 2→ 5I 8 transition of the ion, has been observed when Ho-doped potassium bismuth gallate glass is optically-excited in the red (∼646 nm). The measured quadratic dependence of the relative 549 nm intensity on pump power demonstrates that the upconversion mechanism is the sequential absorption of two photons. For a pump power of 285 mW at 646 nm, the upconversion efficiency is measured to be 5.5% which is among the highest values reported for glassy or crystalline matrices.

Femtosecond optical Kerr shutter using lead–bismuth–gallium oxide glass

Abstract A femtosecond Kerr shutter was demonstrated using a lead–bismuth–gallate oxide glass. The optical gating time was measured to be less than 350 fs and the peak Kerr transmittance was found to be 2.3 times larger than that of the standard Kerr CS 2 liquid medium, giving nonlinear Kerr coefficient n 2 =4.4×10 −11 esu.

Erbium-doped potassium bismuth gallate glasses

We demonstrate potassium bismuth gallate glasses as suitable hosts for rare-earth-ion erbium (Er3+) operating in the 1.55-µm-wavelength region. The absorption and luminescence spectra along with the luminescence decay time were measured. The emission peak of the 4I13/2→4I15/2 transition is at the 1.53-µm wavelength, and the spectral bandwidth is 85 nm, which is one of the broadest. The lifetime of the 4I13/2 level is ∼2.42 ms, and the quantum efficiency is ∼100%. The emission cross section is estimated to be ∼12.4×10-21 cm2, which is one of the highest among different oxide glasses. The gain coefficient is also calculated, and our results show that potassium bismuth gallate glasses are excellent host materials for broadband-amplifier and high-power-laser applications.

Upconversion luminescence of Er3+ in alkali bismuth gallate glasses

Frequency upconversion of Er3+ in alkali bismuth gallate glasses have been investigated. The upconversion mechanisms are discussed, and the dominant mechanisms are excited state absorption for the H11/22→I15/24 and S3/24→I15/24 transitions, and energy transfer upconversion for the F9/24→I15/24 transition. Intense green (around 525–550 nm) and red (around 660 nm) emission bands were observed under 800 nm excitation. At a pump intensity of 15.6 W/cm2, frequency upconversion efficiencies of 2.1×10−2 and 4.8×10−3 were obtained for the green and red emissions, respectively. The results are the highest among doped oxide glasses, and are comparable to those reported for Er3+/Yb3+ codoped fluoride glasses.

Praseodymium-doped alkali bismuth gallate glasses

We propose and demonstrate alkali bismuth gallate glasses as suitable hosts for the rare earth praseodymium (Pr3+) operating at 1.3-µm wavelength. The structure of the glasses was investigated by Raman spectroscopy. The optical absorption and the photoluminescence properties of Pr3+ in these glasses were characterized. The Raman spectrum shows two strong peaks, at 134 and 381 cm-1, and a weak peak at 660 cm-1. The results indicate that bismuth (Bi3+) and gallium (Ga3+) cations do take part in the formation of the glass network. The emission from the Pr3+: 1G4→3H5 transition is at 1.34-µm wavelength, and the spectral bandwidth is 120 nm, which is wider than those of fluoride and chalcogenide glasses. The lifetime of the 1G4 level is ∼78 µs, and the quantum efficiency is ∼17.4%, which is higher than that in fluoride glasses.

Compositional Dependence of Optical Properties of Nd<sup>3+</sup> in Gallate Glasses

The Judd-Ofelt parameters, spontaneous emission probabilities from the 4F3/2 level, quantum efficiency, and stimulated emission cross section of the 4F3/2→4I11/2 transition for Nd3+ are studied for potassium tantalum and lead bismuth gallate glasses. The results reveal that the tantalum gallate glasses have high Ω2 values being comparable to that of Ge-Ga-S glass. The lead bismuth gallate glasses have high stimulated emission cross sections over 4pm2 because of their high refractive indexes. The variations of the JO parameters with composition are discussed in terms of glass structure.

Effects of substances inhibiting or uncoupling respiratory-chain phosphorylation of Helicobacter pylori

The effects of electron transport inhibitors and uncoupling agents as well as of bismuth compounds on the respiratory activity and oxidative phosphorylation of Helicobacter pylori were investigated. Bismuth gallate and bismuth subsalicylate reduced the respiratory chain-dependent phosphorylation. Inhibition was of the same magnitude as that observed with other known inhibitors. It is concluded that bismuth displays an antibacterial effect by inhibiting the respiratory chain of H. pylori.

Bismuth absorption from 205Bi-labelled pharmaceutical bismuth compounds used in the treatment of peptic ulcer disease.

The absorption of bismuth from five 205Bi-labelled pharmaceutically used bismuth compounds was studied in man. From single oral doses of all compounds under investigation only less than 0.1% bismuth was absorbed and excreted with the urine. A significantly higher absorption was observed from the colloidal bismuth subcitrate (0.042% of the dose) and the basic bismuth gallate (0.038%) than from the basic bismuth salicylate, nitrate, and aluminate (0.005-0.002%). No retention of bismuth in the whole body was found from the single dose experiment. The biologic fast-term half-lives of absorbed bismuth were calculated to be 0.12 and 1.5 days.

Bioavailability of bismuth from205Bi-labelled pharmaceutical oral Bi-preparations in rats

The bioavailability of 205Bi from various 205Bi-labelled pharmaceutical oral bismuth preparations was studied in rats. The intestinal absorption, calculated from 205Bi whole body retention and accumulated 205Bi urinary excretion, was small in general, but significantly higher (0.26-0.33% of dose) from oral bismuth citrates (basic bismuth citrate, colloidal bismuth subcitrate) as compared to basic bismuth nitrate, salicylate, gallate, and bismuth aluminate (0.04-0.11% of dose). After oral administration, the retained bismuth was mainly accumulated in the kidney, followed by bone, red blood cells and the lung. The whole body retention, faecal and urinary excretions of 205Bi were described by a three-compartment model. Biological 205Bi half-lives of 10, 36 and 295 h were derived in rats.

The growth of single crystalline waveguiding thin films of piezoelectric sillenites

We report for the first time the epitaxial growth of single crystalline thin films of bismuth gallate 12 Bi 2O 3 : 1 Ga 2O 3 and bismuth titanate, 6 Bi 2O 3 : 1 TiO 2. The growth process takes advantage of the difference in the melting points between bismuth germanate, Bi 12GeO 20, the substrate, and that of several lower melting isostructural bismuth compounds as the film material. Liquid phase epitaxial growth via dipping can be made directly in melts of the desired film composition and requires no additional fluxes to effect solubility. The indices of refraction of the films can be made greater than that of the substrate, thus the waveguiding characteristics of the films can be combined with their acoustooptic, electrooptic and nonlinear optic properties. Waveguiding thin films of bismuth gallate and bismuth titanate have been deposited on bismuth germanate substrates in thicknesses ranging up to 100 μm and at growth rates in the order of 1–2 μm/min. These epitaxial layers appear to possess excellent waveguiding characteristics. Using a rutile prism-film coupler, waveguide modes have been observed at 0.6328, 0.5145 and 0.4880 μm laser wavelengths.