E. V. Kolobkova

Characterization of Er-doped sodium-niobium phosphate glasses

Er-doped sodium-niobium phosphate glasses have been produced by the melting technique. Their optical properties have been fully characterized and show a broad fluorescence band around 1.5 micrometers . The fluorescence lifetime of the 4I13/2 metastable state is long enough to make these glasses suitable to be used in optical ampl9ification devices. Waveguides have been produced by diluted Ag+/Na+ ion exchange and their properties are described here.

Fluorophosphate glasses containing PbSe quantum dots

The specific features in the formation of IV–VI (PbSe) quantum dots in a vitreous fluorophosphate matrix are investigated by X-ray microanalysis, high-resolution scanning transmission electron microscopy (STEM), high-resolution X-ray diffraction, and optical absorption spectroscopy. A complete characterization of the quantum dots grown (their sizes, morphology, and distributions over the matrix bulk and sizes) in the glass is performed on the basis of the results obtained. The inference is made that spherical PbSe nanocrystals with a cubic lattice of the NaCl type are formed in fluorophosphate glasses. The nanocrystals are uniformly distributed over the matrix bulk and are characterized by a narrow size distribution (ΔR/R ≈ 7%) in the studied size range R ≈ 1.8–10 nm, which corresponds to strong quantum confinement. It is noted that the mechanism of the quantum-dot growth in the glasses under consideration differs from the mechanisms studied earlier in glasses of silicate systems.

Spectral Luminescence Properties of Transparent Lead Fluoride Nanoglassceramics Doped with Erbium Ions

Transparent nanoglassceramics has been synthesized based on lead fluoride silicate glass doped with erbium ions. It is shown that heat treatment of lead fluoride silicate glass leads to the formation of nanoscale (16–40 nm) crystalline phase of lead fluoride. X-ray diffraction analysis and measurement of spectral luminescence properties have revealed that the erbium ions enter the crystalline phase of lead fluoride.

Formation and Growth of Semiconductor Nanocrystals in Phosphate Glass Matrix

Abstract Phase decomposition of the oversaturated solid solution of semiconductors in glass and the evolution of the ensembles of nanocrystals formed in the media are studied with optical absorption spectroscopy and modeled theoretically. Observed in the experiments difference of temporal behavior of the mean size of the nanocrystals for different levels of the oversaturation coincides with the results of numerical calculations within the frames of the model developed.

Fluorophosphate glasses doped with PbSe quantum dots and their nonlinear optical characteristics

A new fluorophosphate glass matrix containing PbSe quantum dots characterized by a narrow size distribution (ΔR/R ∼ 5–7%, where R is the size of a quantum dot) is prepared under heat treatment. It is demonstrated that fluorophosphate glasses can be doped by introducing (ZnSe + PbO) or PbSe into the composition of the glass. The optical absorption spectra of the quantum dots corresponding to the strong quantum confinement regime are studied over a wide range of quantum-dot sizes (4–18 nm). The nonlinear optical absorption is investigated at a wavelength of 1.54 μm. It is revealed that the introduction of (ZnSe + PbO) rather than of PbSe into the composition of the glass improves the bleaching contrast owing to a more uniform distribution of the quantum dots over the volume of the glass sample.

Optical glass-ceramics based on fluorine-containing silicate glasses doped with rare-earth ions

Oxyfluoride silicate glasses in the SiO2-Al2O3(AlF3)-CdF2-PbF2-ZnF2-Eu2O3 system are studied. Glass-ceramic materials with special properties promising for use of these glass-ceramics as active optical media are synthesized from the oxyfluoride glasses under investigation. The physicochemical and spectral-luminescence properties of the glass-ceramic materials synthesized are investigated. It is shown that the composition of glasses and, consequently, their thermal and physical properties depend on the synthesis conditions. Heat treatment of glasses doped with Eu3+ ions at temperatures somewhat higher than the glass transition point Tg leads to the formation of β-PbF2 nanocrystals such that the major part of the dopant enters into the nanocrystal composition.

Fluorophosphate glasses with quantum dots based on lead sulfide

The specific features in the formation of IV–VI (PbS) quantum dots in a vitreous fluorophosphate matrix are investigated by X-ray microanalysis, high-resolution scanning transmission electron microscopy (STEM), high-resolution X-ray diffraction, and optical absorption spectroscopy. A complete characterization of the nanocrystals grown (their sizes and morphology) in the glass is performed on the basis of the results obtained. It is demonstrated that spherical PbS nanocrystals with a cubic lattice of the NaCl type are formed in fluorophosphate glasses synthesized. The nanocrystals are uniformly distributed over the matrix bulk and are characterized by a narrow size distribution (ΔR/R ≈ 7%) in the studied size range R ≈ 2.0–15 nm, which corresponds to strong quantum confinement.

Formation of II—VI nanocrystals in a novel phosphate glass

A novel glass system was designed for doping with increased concentration of II—VI nanocrystals. CdS, CdSe, CdS x Se 1~x , CdTe and ZnSe crystallites were successfully grown within the glass matrix. High concentration and narrow size distribution of the nanocrystals provide observation of complicated structure of optical transitions. Positions of optical absorption peaks observed for pure semiconductors are compared with results of numerical calculations performed in accordance with existing models of energy levels in the quantum dots. The necessity to take account of the spin—orbit splitting of valence subbands for identification of the observed optical transitions is shown. ( 1998 Elsevier Science B.V. All rights reserved.

Spectral luminescence and information characteristics of transparent lead fluoride nano-glass-ceramics doped with erbium ions

Spectral luminescence properties of synthesized transparent nano-glass-ceramics doped with erbium ions are studied. It is shown that, as a result of the secondary heat treatment of nano-glass-ceramics, the width of the luminescence spectrum at half maximum increases more than by 15 nm. Luminescence life-time dependences of erbium ions in studied samples are measured, their absorption cross-sections are determined, and their emission cross-sections are calculated by the McCumber method. Spectral and ultimate information characteristics of erbium-doped fiber amplifiers based on synthesized nano-glass-ceramics are numerically simulated. It is shown that, in the unsaturated gain regime, a substantial ripple of the absorption and emission cross-section spectra and shorter lifetime of the metastable level of the erbium ion reduce the pumping radiation power that is required for obtaining the given peak gain, narrow the gain spectra, and lower the transmission capacity of devices based on nano-glass-ceramics compared to the initial glass. Conversely, fiber amplifiers based on calcium fluoride glass-ceramics, for which the lifetime of the metastable level increases with increasing annealing temperature, have an advantage in the transmission capacity over devices based on the primary glass.

Specific Features of the Growth of CdSe Nanocrystals in Fluorophosphate Glasses

The choice of the composition of the fluorophosphate vitreous matrix used for optimizing the growth of CdSe nanocrystals with a narrow size distribution is justified. Investigation of the X-ray diffraction parameters has revealed that nanocrystals with sizes varying over a wide range have a hexagonal structure. The evolution of the absorption spectra of fluorophosphate glasses containing CdSe semiconductor nanocrystals is studied. It is shown that the growth mechanism of CdSe nanocrystals differs radically from the nucleation mechanism. The time dependences of the nanocrystal size exhibit an intricate three-stage behavior. The first stage is accompanied by a shift in the absorption spectrum toward the long-wavelength range. After the first stage, the time dependences are characterized by “fast” and “slow” portions. In the fast portion, the exponent of the time dependence of the nanocrystal size increases from 0.4 to 1.0 with an increase in the annealing temperature. The assumption is made that the spinodal decomposition of phases under hyperbolic diffusion occurs in the system under investigation.