Infrared and visible fluorescence in Er3+-doped gallium tellurite glasses

The Effect of Fluorides (BaF2, MgF2, AlF3) on Structural and Luminescent Properties of Er3+-Doped Gallo-Germanate Glass

The effect of BaF2, MgF2, and AlF3 on the structural and luminescent properties of gallo-germanate glass (BGG) doped with erbium ions was investigated. A detailed analysis of infrared and Raman spectra shows that the local environment of erbium ions in the glass was influenced mainly by [GeO]4 and [GeO]6 units. Moreover, the highest number of non-bridging oxygens was found in the network of the BGG glass modified by MgF2. The 27Al MAS NMR spectrum of BGG glass with AlF3 suggests the presence of aluminum in tetra-, penta-, and octahedral coordination geometry. Therefore, the probability of the 4I13/2→4I15/2 transition of Er3+ ions increases in the BGG + MgF2 glass system. On the other hand, the luminescence spectra showed that the fluoride modifiers lead to an enhancement in the emission of each analyzed transition when different excitation sources are employed (808 nm and 980 nm). The analysis of energy transfer mechanisms shows that the fluoride compounds promote the emission intensity in different channels. These results represent a strong base for designing glasses with unique luminescent properties.

Effect of Yb3+ on the Structural and Visible to Near-Infrared Wavelength Photoluminescence Properties in Sm3+-Yb3+-Codoped Barium Fluorotellurite Glasses

We report on the Sm³⁺ and Sm³⁺:Yb³⁺-doped barium fluorotellurite glasses prepared using the conventional melting and quenching method. The spectroscopic characterisations were investigated with Raman and FTIR to evaluate the glasses’ structural and hydroxyl (-OH) content. The Raman analysis revealed a structural modification in the glass network upon adding and increasing the Yb³⁺ concentration from a TeO₃ trigonal pyramid to a TeO₄ trigonal bi-pyramid polyhedral. At the same time, the FTIR measurements showed the existence of -OH groups in the glass. Thus, under the current experimental conditions and nominal composition, the -OH group contents are too large to enable an effective removal. The near-infrared region of the absorption spectra is employed to determine the nephelauxetic ratio and bonding parameters. The average nephelauxetic ratio decreases, and the bonding parameter increases with the increasing Yb³⁺ content in the glasses. A room temperature visible and near-infrared photoluminescence ranging from 500 to 1500 nm in wavelength and decay properties were investigated for glasses doped with Sm³⁺ and Sm³⁺-Yb³⁺ by exciting them with 450 and 980 nm laser sources. Exciting the Sm³⁺- and Sm³⁺-Yb³⁺-doped glasses by 450 nm excitation reveals a new series of photoluminescence emissions at 1200, 1293, and 1418 nm, corresponding to the ⁶F_11/2 state to the ⁶H_J (J = 7/2, 9/2, 11/2) transitions. Under the 976 nm laser excitation, a broad photoluminescence emission from 980 to 1200 nm was detected. A decay lifetime decreased from ~244 to ~43 μs by increasing the Yb³⁺ content, ascribing to concentration quenching and the OH content.

Enhanced Photoluminescence and Photocatalytic Efficiency of La-Doped Bismuth Molybdate: Its Preparation and Characterization

Herein, a systematic study of the enhanced physicochemical properties of lanthanide doped (La-doped) bismuth molybdate (Bi₂MoO₆) is performed. For this purpose, Bi₂MoO₆ and La-doped Bi₂MoO₆ were prepared by the sol-gel method. BiCl₃, Na₂MoO₄^·2H₂O, and LaCl₃·7H₂O were taken as the main precursors while sodium dodecyl sulfate was used as a surfactant. Both Bi₂MoO₆ and La-doped Bi₂MoO₆ were calcined at 650 °C for 2 h. These prepared materials were characterized by spectroscopic techniques such as UV–VIS, FT-IR, XRD, photoluminescence, XPS, along with other techniques such as SEM, TEM, TGA, etc. The investigation of luminescence behavior revealed that the La-doped Bi₂MoO₆ nanocomposite exhibited much greater luminescence compared to the undoped Bi₂MoO₆. The photocatalytic behavior of the prepared materials was explored by studying the degradation of methylene blue (MB) at room temperature. The degradation of MB with Bi₂MoO₆ and La-doped bismuth molybdate were observed to be 68% and 75% @ 45 s, respectively, indicating an enhancement of catalytic performance due to the La doping.

Investigations on spectroscopic properties of Er(3+)-doped Li-Zn fluoroborate glass

Er(3+)-doped Li-Zn fluoroborate glass was synthesized via melt quenching technique. Optical properties of the glass were investigated by UV-Vis-NIR absorption and emission spectra. To evaluate the nature of Er(3+)-ligand bond in the glass network, nephelauxetic ratios and bonding parameter were calculated. Judd-Ofelt analysis and hence the radiative properties of the present glass system were evaluated for ascertaining the suitability of the glass for laser applications and compared those with the emission spectra. Absorption cross-sections have been calculated from the absorption spectrum and stimulated emission cross-sections were estimated using McCumber theory for (4)I13/2↔(4)I15/2 transitions. The results of the present glass were compared with those obtained for some other Er(3+)-doped glass systems.

Intense near-infrared emission of 1.23 μm in erbium-doped low-phonon-energy fluorotellurite glass

Intense near-infrared emission located at 1.23 μm wavelength originating from the erbium (Er(3+)):(4)S3/2→(4)I11/2 transition is observed in Er(3+)-doped fluorotellurite glasses. This emission is mainly contributed by the relatively low phonon energy of the fluorotellurite glass host (~776 cm(-1)). Judd-Ofelt analysis indicates a strong asymmetry and covalent environment between Er(3+) ions and ligands in the host matrix. The emission cross-section was calculated to be 2.85×10(-21) cm(2) by the Füchtbauer-Ladenburg equation, and the population inversion is realized according to a simplified evaluation. The results suggest that the fluorotellurite glass system could be a promising candidate for the development of optical amplifiers and lasers operating at the relatively unexplored 1.2 μm wavelength region.

Investigation of spectroscopic properties, structure and luminescence spectra of Sm3+ doped zinc bismuth silicate glasses

The glasses with compositions 20ZnO·(79.5-x)Bi2O3·xSiO2·0.5Sm2O3 (10≤x≤50, mol%) have been synthesized using normal melt-quench technique. Optical absorption and fluorescence spectra of the glasses were recorded at ambient temperature. Judd-Ofelt (J-O) theory has been successfully applied to characterize the absorption and luminescence spectra of these glasses. From the measured intensities of absorption bands of these glasses, the Judd-Ofelt parameters, Ωλ (λ=2, 4, 6) have been evaluated. The variation of Ω2 with Bi2O3 content has been attributed to changes in the asymmetry of the ligand field at the rare earth (RE) ion site (due to structural change) and to changes in RE-O covalency, whereas the variation of Ω6 is found to be strongly dependent on nephlauxetic effect. The shift of the hypersensitive band shows that the covalency of the RE-O decreases with decrease in Bi2O3 content in the host glass. Also, using J-O theory various radiative properties like spontaneous emission probability (Arad), radiative life time (τr), fluorescence branching ratio (βr) and stimulated emission cross-section (σ) for various emission bands of these glasses in the visible spectral region have been determined. A close correlation is observed between the Bi2O3 content and the spectroscopic, radiative and structural properties of the prepared glasses. The values of radiative properties indicated that 4G5/2→6H7/2 and 4G5/2→6H9/2 transitions responsible for orange luminescence might be used in the development of materials for LED's and other optical devices in the visible region.

Spectroscopic investigations on Pr³+ and Nd³+ doped strontium-lithium-bismuth borate glasses

Spectroscopic investigations on different concentrations (0.1, 0.5, 1.0, 1.5 and 2.0mol%) of Pr(3+) and Nd(3+) doped strontium lithium bismuth borate glasses have been done. X-ray diffraction, SEM with EDS, absorption and luminescence spectra were recorded for all the glass matrices and analyzed. X-ray diffraction profiles and SEM images conformed amorphous nature of investigated glass samples. EDS spectra of host glass and Pr(3+)doped glass matrices gave information about the chemical composition of glass samples. From the absorption spectra of Pr(3+) and Nd(3+) ions, Judd-Ofelt (J-O) intensity parameters (Ω(λ),λ=2, 4 and 6) have been calculated and compared with other glass matrices. The emission characteristics such as radiative lifetimes (τ(R)), measured and calculated branching ratios (β) and stimulated emission cross-sections (σ(P)) have been obtained for the observed emission transitions of Pr(3+) and Nd(3+) ions in the above glass matrix for all the concentrations. From the emission spectra of Pr(3+) and Nd(3+) doped glass matrices, the effect of concentration on the quenching of intensity of (1)D(2)→(3)H(4) transition of Pr(3+) ion and (4)F(3/2)→(4)I(9/2), (4)I(11/2) and (4)I(13/2) transitions of Nd(3+) have been studied and discussed.

Nephelauxetic effect of low phonon antimony oxide glass in absorption and photoluminescence of rare-earth ions

An antimony oxide based monolithic glass with very high Sb2O3 content (70 mol%) in the system K2O-B2O3-Sb2O3 (KBS) has been prepared for the first time. Its phonon energy (602 cm(-1)), evaluated by infrared reflection spectroscopy, is found to be very close to that of fluoride glasses (500-600 cm(-1)). After doping with different rare-earth ions, their UV-vis absorption and photoluminescence properties have been explored, compared with those observed in other hosts and justified with quantitative calculation of nephelauxetic parameter and covalent bonding characteristics. It is been proposed that tunable laser or new color visible light sources may be obtained by controlling these fundamental properties of the glass host. The results also suggest that KBS glass may be used as hosts in the place of fluoride glasses. The Judd-Ofelt parameters, Ωt=2,4,6 for Nd3+, Ho3+, and Er3+ doped in KBS glass have been evaluated and compared with other glasses. It is established that Ωt=2 value follow a direct relationship with covalent character of the hosts which not only supports the above calculation but also provides a generalized evidence for the sensitivity of this parameter to their bonding characteristics.

Optical and dielectric properties of isothermally crystallized nano-KNbO3 in Er3+-doped K2O-Nb2O5-SiO2 glasses

Precursor glass of composition 25K(2)O-25Nb(2)O(5)-50SiO(2) (mol%) doped with Er(2)O(3) (0.5 wt% in excess) was isothermally crystallized at 800 degrees C for 0-100 h to obtain transparent KNbO(3) nanostructured glass-ceramics. XRD, FESEM, TEM, FTIRRS, dielectric constant, refractive index, absorption and fluorescence measurements were carried out to analyze the morphology, dielectric, structure and optical properties of the glass-ceramics. The crystallite size of KNbO(3) estimated from XRD and TEM is found to vary in the range 7-23 nm. A steep rise in the dielectric constant of glass-ceramics with heat-treatment time reveals the formation of ferroelectric nanocrystalline KNbO(3) phase. The measured visible photoluminescence spectra have exhibited green emission transitions of (2)H(11/2), (4)S(3/2)-->(4)I(15/2) upon excitation at 377 nm ((4)I(15/2)-->(4)G(11/2)) absorption band of Er(3+) ions. The near infrared (NIR) emission transition (4)I(13/2)-->(4)I(15/2) is detected around 1550 nm on excitation at 980 nm ((4)I(15/2)-->(4)I(11/2)) of absorption bands of Er(3+) ions. It is observed that photoluminescent intensity at 526 nm ((2)H(11/2)-->(4)I(15/2)), 550 nm ((4)S(3/2)-->(4)I(15/2)) and 1550 nm ((4)I(13/2)-->(4)I(15/2)) initially decrease and then gradually increase with increase in heat-treatment time. The measured lifetime (tau(f)) of the (4)I(13/2)-->(4)I(15/2) transition also possesses a similar trend. The measured absorption and fluorescence spectra reveal that the Er(3+) ions gradually enter into the KNbO(3) nanocrystals.