Doped Lead Germanate Glasses Research Articles

Effect of Al2O3 on structural and luminescent properties of neodymium (Nd3+) doped lead germanate glasses

The conventional rapid melt quenching method was used to prepare neodymium doped alumina lead germanate glasses. Different physical parameters of these glass materials such as density, molar volume, electronegativity, optical basicity and refractive index were calculated. Structural, optical, electrical and dielectric properties of neodymium doped GeO2-PbO-PbF2 glasses with increasing concentration of Al2O3 were studied and reported. X-ray diffraction studies confirmed that the prepared samples were non-crystalline in nature. Surface morphology revealed that the glass materials prepared have similar surface topography. The optical absorption edge observed at 610.5 nm for neodymium glass materials shifted to higher wavelength region with increasing concentration of Al2O3 up to 1.0 mol%, beyond the concentration shift towards shorter wavelength region. The intensity of the luminescence peak was observed around 1090 nm corresponding to 4F3/2 - 4I11/2 transition. The observed functional values of analyzed CIE chromaticity from the luminescence spectra were suggested that the prepared samples were used as white photoemission sources.

Structural and spectroscopic studies on lead germanate glasses doped with V2O5

Vanadium doped lead germanate glasses were synthesized by melt quenching technique. The samples were characterised by XRD and DSC patterns. Optical absorption and ESR studies of the samples indicated that a considerable proportion of vanadyl ions exist in V4+ and V5+states due to substitution of germanate ions with vanadium. The IR spectra of samples have proved the existence of various conventional germanium and vanadium structural units. The variations observed as a function of mol% of dopant in all these studies were analysed keeping in view of different oxidation states and environment of vanadium ions in the glass network.

Photoluminescence Studies of Pr3+ Doped Lead Germanate Glass

The Pr(3+)doped PbO-GeO(2) glass samples have been synthesized by melting and quenching process. The nephelauxetic ratio, covalency and bonding parameter which provides the information about the type of bonding between the rare earth ion and neighbor oxygen atoms calculated. The optical parameters such as radiative transition probabilities, radiative lifetime, branching ratios etc. of Pr(3+) ions have been determined by Judd-Ofelt analysis. An upconversion emission using the excitation at ~594 nm supported by energy transfer process due to dipole-dipole interaction in the (1)D(2) metastable state has been found.

Optical Spectroscopy and Frequency Upconversion Properties of Er3+ Doped Lead Germanate Glass

Optical Spectroscopy and Frequency Upconversion Properties of Er3+ Doped Lead Germanate Glass

Optical transitions in Er 3+ doped lead germanate glasses

Er3+- and Er3+/Yb3+-doped lead germanate glasses that are suitable for use in fibre lasers and optical amplifiers as well as optical waveguide devices have been fabricated and characterized. The absorption spectra from near-infrared to visible were obtained and the Judd–Ofelt parameters were determined from the absorption band. Intense and broad 1.53μm infrared fluorescence and visible upconversion luminescence were observed under 976 nm diode laser excitation. For 1.53μm emission band, the full widths at half-maximum are 36, 37, 51 nm for GPE, GPYE and GPFE samples, respectively. For frequency upconversion emission, the intense bands centred at around 524, 545, 657nm are due to the 4S3/2+2H11/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ ions. The quadratic dependence of the green and red emissions on excitation power indicates that the two-photon absorption process occurs under the 976nm excitation.

Site-selective spectroscopy of Eu 3+ doped lead germanate glasses

A series of lead germanate glasses of molar compositions ( x−1)PbO–(100− x)GeO 2–1Eu 2O 3 with x=30, 40 and 50 were prepared and studied by laser-induced fluorescence line narrowing (FLN) techniques. The energies of the Stark levels of the 7 F 1 and 7 F 2 multiplets were obtained from experimental FLN spectra and a crystal field (CF) analysis was carried out for each excitation energy. The dependence of the CF B kq parameters on the excitation energy is qualitatively similar to the behaviour observed for Eu 3+ in other oxide glasses. The CF calculated ratios B 22/ B 20 and B 44/ B 40 agree reasonably well with the trend predicted by the Brecher and Riseberg geometric model. The CF strength parameter S decreases with increasing lead content in the glass host. This behaviour is explained on the basis of the tendency of lead to form strongly directional Pb–O bonds. On the basis of the present CF analysis, we find no evidence of changes of the local structure at the Eu 3+ sites on increasing the amount of lead and also of 6-fold co-ordinated germanium.

Energy transfer and upconversion processes in Nd^3+-doped GeO_2–PbO–Nb_2O_5 glass

The optical properties of Nd3+-doped lead germanate glass of composition (in mol. %) 60GeO2–25PbO–15Nb2O5 have been investigated for several Nd3+ concentrations at various temperatures by steady-state and time-resolved laser spectroscopy. Judd–Ofelt parameters were derived from the absorption spectrum and used to calculate the 4F3/2→4I11/2 stimulated-emission cross section and the 4F3/2 radiative lifetime. The spectral features of the time-resolved fluorescence line narrowing 4F3/2→4I9/2 emission spectra obtained under resonant excitation reveal the existence of spectral migration of excitation among the Nd3+ ions. Analysis of the time evolution of the 4F3/2→4I9/2 narrowed emission showed that the electronic mechanism responsible for the ion–ion interaction can be identified as a dipole–dipole energy-transfer process. Green, orange, and red emissions were observed in this glass under continuous-wave infrared laser excitation and are attributed to transitions from the 4G7/2 level.

Spectroscopic properties of Pr3+ ions in lead germanate glass

The visible luminescence of Pr3+-doped lead germanate glass of composition (in mol%) 60PbO-40GeO2 has been investigated for two Pr3+ concentrations at different temperatures by using steady-state and time-resolved laser spectroscopy. Concentration quenching of the 1D2 emission is observed for Pr3+ concentrations higher than x = 0.05 mol% even at 4.2 K and attributed to a cross relaxation process. Anti-Stokes emission from the 3P0 level following excitation of the 1D2 state has been observed for the sample doped with 0.5 mol% of Pr3+. The temporal behaviour of the anti-Stokes emission from the 3P0 level following excitation of the 1D2 state suggests that energy transfer is responsible for the upconversion process.

New class of fibre laser based on lead-germanate glass

The first fibre laser based on rare-earth doped lead-germanate glass is reported. The thulium-doped fibre had a background loss of 2 dB/m and a maximum phonon energy of ~920 /cm. Lasing was achieved on the Tm3+ 3H4 - 3H6 transition at 1.905µm with a 3.6mW threshold, when diode-pumped at 790nm. A quantum efficiency of 30% was obtained.