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ErF3-doped TeO2–Ga2O3–BaF2–AlF3–Y2O3 (TGBAY) glasses with high fluorescence efficiency and a high thermal damage threshold were developed for potential mid-infrared fiber laser applications. A model 2.7-μm fiber laser based on this material was analyzed using rate and propagation equations. Under 808 and 980 nm laser pumping, fluorescence emissions with central wavelength at 1.55 and 2.73 μm were detected. Based on the Judd–Ofelt (J–O) theory, the intensity parameters (Ωλ, λ = 2, 4, and 6) and radiative transition property were calculated and characterized through absorption and emission spectra. The results indicated that tellurite–gallium oxyfluoride glass had a high glass transition temperature (Tg, ∼391 °C), large emission cross sections at 1.55 μm (6.32 × 10−21 cm2) and 2.73 μm (9.68 × 10−21 cm2) as well as a longer fluorescence lifetime (6.84 ms at 1.55 μm and 262 μs at 2.73 μm) relative to the conventional Er3+-doped tellurite glass. The temperature dependence of the emission spectra indicated that TGBAY-2Er glass was more favorable to achieve infrared emission at low temperatures. Numerical simulation revealed the feasibility of achieving a ∼2.7 μm fiber laser operation based on the developed Er3+-doped tellurite–gallium oxyfluoride glass fiber. [ABSTRACT FROM AUTHOR]

A group of highly Er3+-doped TeO 2 –BaF 2 –LaF 3 –La 2 O 3 fluorotellurite glasses was prepared by high-temperature melting and rapid cooling. The Judd-Ofelt (J-O) theory intensity parameters, radiative transition rate, and radiative lifetime of Er3+ ions were calculated based on the absorption spectra. The luminecence spectra at 2.7 μm and luminescence lifetime curves of Er3+ ions in fluorotellurite glasses, excited at 980 nm, were studied. The fluorotellurite glass exhibits high infrared transmittance (88 %), excellent thermal stability (ΔT > 105 °C), and low phonon energy (781 cm-1). According to Fuchbauer-Ladenburg theory, the absorption and emission cross sections of Er3+-doped fluorotellurite glass at 2.7 μm are 5.50×10−21 and 6.28×10−21cm2, respectively. These findings suggest that the glass holds significant potential for applications in mid-infrared (MIR) fiber lasers. • The fluorotellurite glass possesses high infrared transmittance (88 %). • The prepared glass exhibits excellent thermal stability (ΔT > 105 °C). • The prepared glass has low phonon energy (781 cm-1). • The fluorotellurite glass exhibits strong luminescence at 2.7 μm. [ABSTRACT FROM AUTHOR]

Abstract Nd3+-doped mixed-anion fluoro-sulfo-phosphate (FPS) glass has been investigated as a laser material in detail. It is found that anion-mixing in Al(PO 3) 3 -BaF 2 -BaSO 4 glass system enables excellent physical properties and chemical durability. Besides, the complicated local environment provided by multi-component leads to high radiative transition probability and influences other luminescent properties considerably. The measured lifetime of Nd3+: 4F 3/2 in FPS is 349.8 μs and the quantum efficiency is 92.91%, higher than those of phosphate and fluoro-phosphate glasses. These results suggest that the FPS glass system could be a promising candidate for 1.06 μm laser source. Highlights • Nd3+-doped fluoro-sulfo-phosphate glass systems were investigated. • Glass-forming regions of the glasses were predicted via the thermodynamic method. • Optical and spectroscopic properties of the FPS glass were investigated. [ABSTRACT FROM AUTHOR]

The influence of erbium ion concentration on the optical properties of BaF2:ErF3 crystals was investigated. Four ErF3 concentration (0.05, 0.08, 0.15 and 0.5 mol% ErF3)-doped BaF2 crystals were obtained using the Bridgman technique. Room temperature optical absorption in the 250–850 nm spectral range was measured, and the photoluminescence (PL) and decay times were also investigated. The Judd–Ofelt (JO) approximation was used, taking into account four absorption peaks (at 377, 519, 653 and 802 nm). The JO intensity parameters, Ωt (t = 2, 4, 6), were calculated. The influence of the ErF3 concentration on the JO parameters, branching ratio, radiative transition probability and radiative lifetime were studied. The obtained results were compared with measured values and with those reported in the literature. Under excitation at 380 nm, the well-known green (539 nm) and red (668 nm) emissions were obtained. The calculated and experimental radiative lifetimes were in millisecond range for green and red emissions. The intensity of the PL spectra varied with the Er3+ ion concentration. The emission intensity increased linearly or exponentially, depending on the ErF3 concentration. Under excitation at 290 nm, separate to the green and red emissions, a new UV emission band (at 321 nm) was obtained. Other research has not reported the UV emission or the influence of ErF3 concentration on emission behavior. [ABSTRACT FROM AUTHOR]

Fluoro phosphate glasses with different contents of barium and bismuth (8, 11, 14, 17 and 20 mol %) doped with Nd3+ were prepared by melt quenching technique. Importance of these modifier ions on structural transformation were carried out using XRD, FTIR, FT-Raman and 31P MAS NMR characterizations. 31P MAS NMR spectra revealed that structural modifications due to Bi 2 O 3 are more when compared with BaF 2 in this fluoro phosphate glass matrix. Three phenomenological Judd-Ofelt (J-O) parameters Ω λ (λ = 2, 4, 6) have been derived from the absorption spectra of Nd3+ doped barium and bismuth fluoro phosphate glasses. From the Judd-Ofelt parameters, transition probabilities (A), branching ratios (β) of certain transitions and radiative lifetimes of certain excited states of Nd3+ are extracted and reported. From the emission spectra, emission cross sections (σ e), band gains (σ e xΔλ eff) and optical gain parameters (σ e xτ R) were reckoned for the observed emission bands in these phosphate glasses. It is observed that barium glass resulted higher laser spectroscopic parameters (σ e , σ e xΔλ eff , σ e xτ R) which are crucial characteristics for exploring promising laser applications. Impact of Ba2+ and Bi3+ on luminescent properties of Nd3+ doped fluoro phosphate glasses has been examined in search of solid sate gain medium for laser emitting NIR light around 1.058 μm for photonic applications. •Nd3+ doped barium and bismuth flouro phosphate glasses are prepared by melt quenching technique. •Structural analysis for present fabricated vitreous material with the help of FT-Raman, FTIR and 31P NMR spectra. •Addition of Alkaline earth fluoride BaF 2 enhance the spectroscopic properties. •The Nd3+ doped Barium flouro phosphate glasses could be promising host in the NIR region around 1.058 μm. [ABSTRACT FROM AUTHOR]

This paper describes the preparation and characterization of various concentrations of Nd3+ doped B 2 O 3 –BaF 2 –PbF 2 –Al 2 O 3 (BaPbAlFB) glasses in detailed. The glasses used in the present work are synthesized by using melt quenching process and characterized by measuring the absorption, photoluminescence (PL) and PL decay spectral profiles. The energies of the absorption spectral profiles called oscillator strengths are evaluated from the absorption spectra and subjected to Judd-Ofelt (J-O) theory to evaluate the J-O intensity parameters using least squares fit method. Under 808 nm diode laser excitation, the BaPbAlFBNd glasses exhibit three emission bands at near-infrared region around 887, 1063, 1336 nm from 4F 3/2 → 4I 9/2, 4I 11/2 and 4I 13/2 radiative transitions respectively. Among the three emissions, the one observed at 1063 nm is found to be more intense relatively. The lifetime of 4F 3/2 transition has been estimated experimentally through decay measurements recorded under 808 nm excitation wavelength. Among all the BaPbAlFB glasses investigated, the one with 1.0 mol% of Nd3+ ions is showing relatively high fluorescence quantum efficiency. The measured saturation intensity (I S) values shows relatively the low threshold values. The obtained results endorsed the potentiality of BaPbAlFBNd1.0 glass for the fabrication of fiber amplifiers and solid-state lasers that can act in NIR region at 1063 nm wavelength. • The J-O intensity parameters of the glass samples. • Experiment lifetimes are calculated from decay measurements. • The evaluation of absorption cross section, emission cross section and gain cross section. • The figure of merit and saturated intensity are calculated. • NIR laser emission near 1.063 μm was obtained. [ABSTRACT FROM AUTHOR]

The spectroscopic properties of the gamma irradiated BaF 2 :Er3+ crystals were studied. BaF 2 :0.2 mol% ErF 3 crystal was grown using the vertical Bridgman method. The Judd-Ofelt intensity parameters, Ω t (t = 2,4,6) for f-f transitions of Er3+ ions were determined from optical absorption spectra recorded before and after gamma irradiation at various doses. The influence of gamma irradiation dose on the Judd-Ofelt parameters and on the radiative transition probability, on the branching ration and on the radiative lifetime was also investigated. The predicted radiative lifetimes were compared with those measured and with those reported by other authors. Apart from the green and red emissions, arising under excitation at 378 nm, a new UV emission band around 321 nm was observed under excitation at 290 nm. This emission was not reported before. Using the Füchtbauer-Ladenburg method, the emission cross section and optical gain parameter of the red and green emission band were calculated. • Good quality BaF 2 :0.2 mol% ErF 3 crystal was grown by Bridgman method. • Gamma rays effects were investigated by optical absorption studies. • The influence of gamma rays on the Judd-Ofelt spectroscopic parameters was investigated. • New UV emission band around 321 nm was observed under excitation at 290 nm. • The calculated radiative lifetimes increase slightly with the gamma dose. [ABSTRACT FROM AUTHOR]

Different doping concentrations of Dy3+/Tm3+ in ZrF 4 -BaF 2 -YF 3 -AlF 3 (ZBYA) fluoride glass samples were prepared by the melt-quenching method. Spectroscopic properties were analyzed through absorption (from 200 to 3300 nm) and emission spectra (from 1200 to 3200 nm). The spontaneous radiative transition probability, branching ratio and radiative lifetime of various energy levels transition were calculated based on the Judd-Ofelt theory. The emission cross-section value of the 1 mol% Dy3+/1 mol% Tm3+ co-doped ZBYA sample at 2.9 μm were calculated as 3.79 × 10−21 cm2. Near- and mid-IR emission spectra of Dy3+/Tm3+ co-doped ZBYA-fluoride glass under the excitation of 808 nm laser diode were investigated and discussed. Analysis of the emission spectra and the energy transition process of Dy3+/Tm3+ co-doped glass indicated that the introduction of Tm3+ ions can effectively improve the mid-infrared fluorescence intensity of Dy3+ ions, thus the Dy3+/Tm3+ co-doped ZBYA-fluoride glass can be an excellent candidate material for 2.9 μm mid-infrared laser applications. • Energy transfer processes between Dy3+ and Tm3+ ions in ZrF 4 -BaF 2 -YF 3 -AlF 3 (ZBYA) fluoride glass samples were investigated in details. • The transmittance of ZBYA glass at λ∼1000–6000 nm is as high as 90%, with an infrared cutoff wavelength at around λ∼9000 nm α OH − in the ZBYA sample is as low as ∼0.0098 cm−1, which is ascribed to the chemical dehydrating process (F− + OH−.→O2− + HF ↑) and longtime physical dehydrating process in ultra-dry pure nitrogen atmosphere. • The introduction of Tm3+ ions improve the mid-infrared emission intensity of Dy3+ ions in ZBYA glass, which is ascribed to the energy transfer process of Tm3+: 3F 4.→ Dy3+:6H 11/2. [ABSTRACT FROM AUTHOR]