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Neodymium doped fluorophosphate (FP:Nd3+) glasses with different chemical compositions (59NH4H2PO4+15ZnO +15BaF2+10X+1·0NdF3 (X=LiF, NaF, CaF2, SrF2, AlF3)) were prepared by melt quenching. Their structures and spectroscopic properties were studied using x-ray diffraction, FTIR, FT-Raman and 31P, 27Al MAS NMR techniques. Various structural groups were identified using FTIR and FT-Raman spectra. The depolymerisation of metaphosphate chains are described by the decrease of Q² tetrahedral sites allowing the formation of pyrophosphate groups revealed by 31P MAS NMR spectroscopic studies. Optical properties were studied using absorption and photoluminescence spectroscopy. Judd–Ofelt intensity parameters Ωλ (λ=2, 4 and 6) were estimated from absorption spectra. Radiative parameters such as transition probabilities (A), radiative lifetimes (τR), integrated absorption cross-sections (Σ) and branching ratios (βR) were calculated. Two emission lines at 1060 and 1330 nm were observed for Nd3+ in all the fluorophosphate glasses. From the emission spectra, emission characteristics were studied via optical band gains (σe×τR)and gain bandwidths (σe×Δλeff). Fairly large numerical values for peak emission cross-sections (σe) and branching ratios (β) for 4 F3/2→4 I11/2 transition of Nd3+ ion doped calcium fluorophosphate glass were observed. These results are rosy for NIR laser application at 1060 nm. [ABSTRACT FROM AUTHOR]

Novel ternary fluoro-germano-tellurite (GTS) glasses doped with Er3+ ions with 0.5 mol% and 1.0 mol% were fabricated by a conventional melt and quenching method and investigated using methods of optical spectroscopy. The room-temperature absorption spectrum was recorded and analyzed to determine radiative transition rates, radiative lifetimes, and branching ratios of Er3+ luminescence. Decay curves of Er3+ luminesccence were recorded and analyzed. Temperature dependences of emission spectra and absorption spectra in the region from RT (room-temperature) up to 675 K were studied in detail. The contribution of competing radiative and nonradiative processes to the relaxation of luminescent levels of Er3+ was assessed. Absolute and relative sensitivity were established utilizing the comprehensive model based on thermally coupled 2H11/2/4S3/2 excited states of erbium. The high quantum efficiency of the first erbium-excited state and value of gain coefficient indicate that GTS:Er glass system can be considered as conceivable NIR (near infrared) laser material as well. [ABSTRACT FROM AUTHOR]

In this work, the visible luminescence of P 2 O 5 -KF-Al 2 O 3 glasses with Tm 2 O 3 was studied. The Tm3+ ion can have a strong blue emission, which allows the development of LEDs in this color region. This study refers to the synthesis of oxyfluorophosphate glasses, 38P 2 O 5 +(50-x)KF+12Al 2 O 3 +xTm 2 O 3 (PKAl:Tm), with x = 0.25, 0.50, 0.75, and 1.00 mol%, by the melt-quenching method. The prepared materials showed amorphous characteristics verified by XRD data. The absorption spectra shown six main bands characteristic of Tm3+ ions, from ground state 3H 6 to excited levels 3F 4 , 3H 4 , 3H 5 , 3F 3,2 , 1G 4 and 1D 2 , in which the intensities increased with the concentration of Tm 2 O 3. In the FTIR spectra, it was verified that the profiles of the PKAl samples are similar to glasses based on phosphate systems. The Judd-Ofelt parameters were calculated, where for PKAl glasses the trend was Ω 2 >Ω 4 >Ω 6. The excitation spectra of PKAl:Tm glasses shown an intense band centered at 358 nm (3H 6 →1D 2). The luminescence spectra with excitation at 358 nm shown two bands at 453 nm (1D 2 →3F 4), and 480 nm (1G 4 →3H 6); the highest emission intensity was observed to the sample doped with 0.75 mol% of Tm 2 O 3. The calculated CIE diagram shown that the doped samples have coordinates close to the primary blue color, which favors the application for the development of blue LEDs and wLEDs. The decay curves for the 1D 2 level were fitted by single exponential with lifetime values decreasing with increasing concentration of Tm 2 O 3. These results show that the PKAl:Tm glasses are potential candidates for applications in LEDs. [Display omitted] • 38P 2 O 5 -(50-x)KF-12Al 2 O 3 -xTm 2 O 3 glasses, x = 0.25, 0.50, 0.75, and 1.00 mol%. • The optical parameters, transition probability and radiative lifetimes were evaluated using the Judd-Ofelt theory. • CIE coordinates appeared in the deep blue regions under 357 excitation, with main emission at 454 nm. • Oxyflorophosphate glasses doped with Tm 2 O 3 are candidates for photonic applications in blue emitters. [ABSTRACT FROM AUTHOR]

With the development of science and the progress of technology, novel and advanced rare earth ions doped luminescent materials with higher performance are demanded in the both emerging and traditional applications. Understanding the rules for tuning the spectroscopic properties of these materials is crucial for their development. However, achieving precise control over the optical properties of rare earth doped materials using traditional design and synthesis methods, such as altering dopants and their concentrations or modifying the preparative conditions, still remains challenging. This work aims to adjust the optical transition characteristics of Er3+ doped germano-tellurite glasses by changing the glass components. First, the Er3+ doped germano-tellurite glass series were synthesized using a high-temperature melt-quenching method at optimized melting temperatures. The tuning of band gap energy and refractive index of the glasses were revealed, and it was found that both of them can be monotonically and continuously tuned by changing the glass composition. The optical transition intensity parameters of Er3+ in the glasses were calculated in the framework of traditional three-parameterized Judd-Ofelt theory using the absorption spectra, and furthermore the corresponding optical transition parameters including radiative transition rates and intrinsic lifetimes for some interested levels were alsoconfirmed. The results demonstrated that the optical transition parameters could be efficiently modulated by changing the glass composition, indicating that the spectral properties of Er3+ doped germano-tellurite glasses can be tuned for the practical applications. The reliability of the deduced tuning rule was validated by comparing the theoretical and experimental transition rate ratios of 2H 11/2 → 4I 15/2 to 4S 3/2 → 4I 15/2. Furthermore, the tuning regulation of the phonon spectra in relation to the glass composition was discovered, showing a concordance between theoretical predictions and experimental results. From the above facts, it can be concluded that the optical transition properties of Er3+ in germano-tellurite glasses can be substantially adjusted by modifying the glass composition. This work provides a new perspective for designing and developing novel luminescent materials to meet specific application needs. • A new route is proposed for developing luminescence materials and tuning their optical properties based on practical demands. • Scope of application of the Judd-Ofelt theory is extended. • Temperature sensing and optical transition properties for Er3+ doped germano-tellurite glasses are successfully tuned. • The tuning regulation of the phonon spectra toward the glass composition was discovered. [ABSTRACT FROM AUTHOR]

Erbium doped phosphate glasses with Li2O-Al2O3-BaO-P2O5-Er2O3 (Li glass) and Na2O-Al2O3-BaO-P2O5-Er2O3 (Na glass) composition were produced using the melt-quench method to determine their spectroscopic properties. The optical absorption and fluorescence spectra were used to analyze the spectroscopic properties. The Judd-Ofelt intensity parameters Ω λ (λ = 2 , 4 , 6) were determined from the absorption band intensities. The Ω2 parameter of a LABPEr glass is 1.50 × 10−20 cm2 that of a glass of s NABPEr glass is 0.41 × 10−20 cm2, which of the LABPEr glass is higher than the NABPEr glass. The radiative transition probability (AR) of LABPEr and NABPEr are 133.03 and 80.38 s−1, respectively. In predicting the emission cross-section (σ e) of 4I13/2→4I15/2 transition from the absorption cross-section (σ a) of 4I15/2→4I13/2 transition for Er3+ ions, the McCumber theory has been adopted. At 1.54 nm, intense broad infrared fluorescence was detected under 980 nm excitation. The optical gain G(λ) properties can be derived from the σa and σe values that the gain is positive for 50% population inversion in the 1536–1640 nm wavelength range. [ABSTRACT FROM AUTHOR]

A series of glasses by melting quenching method fabricated for spectroscopic investigations of Dysprosium (Dy3+) particle ions deposited on Antimony (Sb) - Magnesium (Mg) - Strontium (Sr) Oxyfluoroborate (BSbMgfSr) glasses. The structural and optical characterizations such as XRD, UV-VIS-NIR absorption spectroscopy, photoluminescence (PL) (excitation and emission) were accomplished to study the properties of prepared glasses. The transitions from lowest energy state to an excited state in RE3+ ions were identified using optical UV-NIR absorption spectra. By the use of Judd-Ofelt theory the J-O intensity parameters Ωλ (λ = 2, 4, 6) have been evaluated utilizing the absorption spectra with the determination of experimental (fexp) and calculated (fcal) oscillator strengths. The emission of light from glass system was concluded through PL spectra (Excitation and emission) for Dy3+ion. The radiative properties resembling radiative transition probability (AR), radiative-lifetime (τR), and branching-ratio (β) of the glasses have also estimated. Stimulated emission cross-section (σse) of the glasses also calculated for the feasibility of lasing applications. Experimental lifetime (τexp) of the decay curves of the BSbMgfSrD glasses were also calculated upon excitation by suitable wavelengths of all various concentrations of the RE3+ ions. [ABSTRACT FROM AUTHOR]

A Pr3+-doped NaGd(WO4)2 single crystal has been grown by the Czochralski technique along the (0 0 1) orientation. The refractive indices were measured precisely as a function of wavelength. A Raman spectrum, polarized absorption spectra, fluorescence spectra, and fluorescence decay curve have been recorded at room temperature. The standard and modified Judd-Ofelt theories have been performed to analyze the absorption spectra to determine the spectroscopic parameters, including the Judd-Ofelt intensity parameters Ωt (t=2,4,6), radiative transition probabilities, radiative lifetimes, and branching ratios. The stimulated emission cross sections and fluorescence lifetime of the promising laser level were obtained. [ABSTRACT FROM AUTHOR]

Large-sized, high optical quality Gd 2 O 3 single crystals were grown from a solution at T = 1145 °C using Czochralski method. XRD analysis showed that the crystal structure is characterized by a single cubic (bixbyite) phase (c -phase). The absorption spectra and luminescence properties of Gd 2 O 3 doped with Eu3+ and Tb3+ impurity ions were studied. The absorption spectrum of Gd 2 O 3 :Eu in the short wavelength region is mainly due to charge transfer transitions from O2− to Eu3+ (240–290 nm), which overlap with the Urbach tail of the host-absorption. Additionally, electronic transitions in Eu3+ (320–540 nm) and Gd3+ (245–315 nm) lanthanide ions contribute to the absorption spectrum. Intraconfigurational radiative f – f transitions in impurity ions are clearly observed upon both UV- and X-ray excitations. However, 6 P J → 8 S 7 / 2 radiative transitions in Gd3+ ions are completely unobservable. Based on the obtained spectroscopic data, the energy positions of the ground state of all di- and trivalent lanthanide ions, as well as the energies of intraconfigurational f – f and interconfigurational f – d electronic transitions in Gd 2 O 3 crystals with a cubic structure, are calculated. The proposed electronic energy diagram is used to discuss efficient energy transfer between lanthanide ions. [Display omitted] • We grew optical quality Gd 2 O 3 single crystals from flux using Czochralski method. • XRD analysis of the Gd 2 O 3 crystals showed monophase cubic structure. • We studied intraconfigurational f – f transitions upon UV and X-ray excitations. • We determined the lowest energy levels of Ln2+ and Ln3+ ions in Gd 2 O 3 crystals. • We revealed efficient energy transfer between lanthanide ions in Gd 2 O 3 crystals. [ABSTRACT FROM AUTHOR]

Absorption, excitation, fluorescence and decay spectra are carried out at room temperature on Er 3+ (1%), Yb 3+ (4%): Cd .7 Sr .3 F 2 mixed single crystals. These crystals, with a good optical quality, are grown by the standard Bridgman method. This work concerns mainly the spectroscopic properties of the Er 3+ ions incorporated in a fluorite-type crystal. Using the room temperature absorption spectra, the standard Judd–Ofelt (JO) model is applied to absorption intensities of Er 3+ to obtain the three phenomenological intensity parameters by the least square fit procedure. The values obtained are in accordance with those of other fluoride hosts with good root mean square fitting. Compared to oxide materials, fluoride materials have, in general, low values ​​of Ω 2 . The low value of Ω 2 is correlated to the cubic nature of the site occupied by the rare earth in the host matrix. These JO intensity parameters are then applied to determine the radiative transition probabilities (A JJ′ ), radiative lifetimes (τ rad ) and branching ratios (β JJ′ ) of Er 3+ transitions. The green emission generated by the Er 3+ ions directly excited in UV level, consisting in three well-resolved major lines, is more intense than the one. We have measured the fluorescence lifetime, the cross-section emission, the gain and the radiative quantum efficiency for both green and red band emissions. The obtained results are in good agreement with those of other fluoride laser crystals. From, the obtained spectroscopic data we suggest that Cd .7 Sr .3 F 2 may offer green and red visible laser emission when doped with Er 3+ ions. [ABSTRACT FROM AUTHOR]

Spectroscopic investigation on the optical characteristics of 1.06 μm (4F 3/2 → 4I 11/2) transition of Nd3+ ions with different concentration in fluoroborosilicate (FBSND) glasses is reported. The glass transition temperature estimated via DSC analysis confirmed the thermal stability of the Nd3+ doped fluoroborosilicate glassy system. The phenomenological Judd-Ofelt parameters were evaluated by implementing the Judd–Ofelt (JO) theory on the recorded absorption spectrum and the parameters. Strong NIR emission has been observed for the lasing transition at 1.06 μm under an excitation of 584 nm. The emission intensity of all the luminescent bands in the NIR emission spectra of FBSND glasses observed to be increased up to 1 mol% and after that a fall in emission intensity is observed due to concentration quenching. Large value of JO intensity parameters and radiative properties such as branching ratio, stimulated emission cross section, radiative transition probability recommends FBSND glasses for photonic applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Far-UV absorption spectra of mono- and multi-layer hBN film. • Deep-UV emissions of mono- and multi-layer hBN by excitation with 180 nm. • Direct and indirect band transitions of hBN thin-films. Hexagonal boron nitrides (hBNs) have a very high luminescence efficiency and are promising materials for deep-UV emitters. Although intense deep-UV emissions have been recorded in various forms of hBN excited by photons or energetic electrons, information on the electronic structure of the conduction band has been derived mainly from theoretical works. Therefore, there is a lack of high-resolution absorption data in the far-UV region. In this study, the far-UV absorption spectra of chemical-vapor-deposition-grown mono- and multilayer hBNs were recorded at 10 and 298 K. In addition to the previously reported band at 6.10 eV, two absorption bands at 6.82 and 8.86 eV were observed for the first time in thin-film hBN. Furthermore, excitation of the hBN thin film samples with 6.89-eV photons revealed intense emission peaks at 6.10 (mono) and 5.98 (multi) eV with a bandwidth of ∼0.7 eV. Comparing the absorption and photoluminescence data, we believe that both direct and indirect transitions occur in the radiative processes. [ABSTRACT FROM AUTHOR]

Abstract: The Judd–Ofelt parameters of Er3+ in the partially disordered calcium lithium niobium gallium garnet are calculated using absorption spectra. The results ( ; ; ) are used to calculate the radiative lifetimes of the Er3+ energy levels up to 4G11/2 and the branching ratios of the radiative transitions originating on them. The luminescence lifetimes of Er3+ excited levels 4I13/2, 4I11/2, 4F9/2, (4S3/2, 2H211/2) and 2H29/2 are also presented. [Copyright &y& Elsevier]

• Reliable potential energy curves for the quintet electronic states of VAr+ and VKr+. • Most complete characterization of these cations states to date. • Dipole and transition moments, einstein A v´v´´ emission coefficients, and radiative lifetimes. • Absorption spectra for the g 5Π – X 5Σ+ band systems modelled with intensity peaks clearly identified. Nine low-lying quintet electronic states of the cations VAr+ and VKr+ are characterized theoretically at the SA-CASSCF/icMRCI/aug-cc-pV5Z level of theory by the construction of potential energy curves and the determination of spectroscopic parameters. The polarity of the molecules is described by dipole moment functions and vibrationally averaged dipole moments. Transition probabilities for spontaneous emission for selected states are estimated by the Einstein A v´,v´´ coefficients and the stronger transitions identified; radiative lifetimes are also reported. For the photoabsorption process, the spectrum is modelled for the bands of the G 5Π – X 5Σ+ system of each species for which experimental photodissociation results are available in the literature. Not known experimentally, the intensity distribution is expected to help elucidate the assumed vibrational numbering of the upper state, and together with the overall electronic description and spectroscopic parameters motivate further experimental investigations of transition metal-rare-gas cations. Binding arises from purely electrostatic charge-induced dipole interaction. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Praseodymium doped lead telluroborate (PTBPr) glasses were prepared by conventional melt quenching method. The absorption spectra have been analyzed to evaluate the intensity parameters applying the standard and the modified Judd–Ofelt theories. The emission spectra under 3P2 level excitation (λ ex =447nm) were investigated to estimate the laser characteristic parameters. These emission measurements together with Judd–Ofelt intensity parameters (Ω λ =2,4,6) have been used to calculate the radiative transition probabilities, fluorescence branching ratios and radiative lifetimes of the transitions from 3P0 and 1D2 levels to their lower lying levels. The quenching of fluorescence intensity and experimental lifetime with the increase of Pr3+ concentration and the shift of 1D2 → 3H4 emission peak towards longer wavelengths was discussed. The non-radiative losses due to multiphonon and energy transfer relaxations were also explained. The Commission Internationale de I''Eclairage (CIE) coordinates, color purity and optical band gap energy values were evaluated. Some of the basic laser characteristics such as stimulated emission cross-section, optical and bandwidth gain parameters and fluorescence quantum efficiency were also reported. [Copyright &y& Elsevier]

Abstract: We report here the results of high accurate, , ro-vibrational analysis of the ethylene molecule in the region of 640–1535cm−1. More than 1110, 5060, 4670, and 2900 transitions belonging to the , , , and bands were assigned in the experimental spectrum with the maximum values of quantum numbers , equal to 36/11, 50/21, 40/17 and 48/17, respectively. Rotational and centrifugal distortion parameters of the ground vibrational state were improved on the basis of assigned transitions and high accurate saturated absorption experimental data known from the literature. The inverse spectroscopic problem was solved for the set of strongly interacting states. The set of 78 parameters obtained from the fit reproduces values of 3644 initial “experimental” ro-vibrational energy levels (more than 13,740 assigned transitions of the , , , and bands) with the rms=0.00023cm−1. In this case, the 197 high accurate saturated absorption transitions are reproduced with the rms=18.5kHz. [Copyright &y& Elsevier]

Abstract: Optical properties of Erbium-doped sodium aluminum telluro–phosphate glasses with compositions of 48P2O5–21Na2O–23Al2O3–(8−x)TeO2–(x)Er2O3 (where x=2–7) were investigated. From the measured optical absorption spectra, Judd–Ofelt (JO) analysis has been carried out to predict radiative properties of doped Er3+ ion luminescent levels. The estimated emission cross sections were found to be more than other commonly available short-length optical amplifier (aluminosilicate) glasses. Relative emission intensity enhancement with the increase of Er3+ ion concentration is observed for the laser transition, 4I13/2→4I15/2 (at 1.53μm). Higher emission lifetimes (4.2–6.23ms), higher quantum efficiencies (44–65%) relative at higher Er3+ ion concentrations, high gain bandwidth and gain per unit length at 1.5μm are the most notable features of these glasses for future optical amplifier applications. [Copyright &y& Elsevier]

Abstract: Optical absorption spectra, emission spectra, and fluorescence lifetimes were measured for a number of visible and infrared transitions in Ho3+ doped KPb2Cl5. Judd–Ofelt parameters were obtained by using the conventional approach, as well as by a modified approach that minimizes the fractional difference, rather than the absolute difference, between calculated and measured oscillator strengths. Both procedures gave good overall agreement between measured and calculated lifetimes, with an average difference of ≈15%. This confirms the expectation from the multiphonon energy gap law that most observed transitions in Ho3+:KPb2Cl5 are highly radiative. Emission cross section spectra for the transitions 5F3 → 5I8, 5G5 → 5I7, 5F3 → 5I7, 5F4/5S2 → 5I7, and 5I7 → 5I8 were obtained from measured emission spectra, with the peak cross section values scaled by the Judd–Ofelt calculated oscillator strengths. [Copyright &y& Elsevier]

Abstract: Effects of WO3 and CdO on the spectroscopic properties of Nd3+ doped tellurite glasses were investigated. The optical band gaps and Urbach energies of the samples were determined using the dependence of the absorption coefficient on the photon energy. The Urbach energies were found to vary from 0.18 to 0.25eV as the WO3 content in the binary glasses decreased from 20.0 to 10.0mol% while the optical band gap of the same glasses did not show an appreciable dependence on the glass composition. Judd–Ofelt (Ω t ) parameters were calculated from the optical absorption spectra measured at room temperature. In all the glasses the J–O parameters follow the same trend as Ω 2>Ω 6>Ω 4. The J–O intensity parameters were used to compute the radiative properties such as the radiative transition probabilities (A ed ), branching ratios (β) and radiative lifetimes (τ r ) for all the possible fluorescence bands. The fluorescence spectra obtained upon 805.2nm excitation exhibited an intense emission band centered at 1064nm (4F3/2→4I11/2) and two weak bands at 910nm (4F3/2→4I9/2), and 1340nm (4F3/2→4I13/2). The stimulated emission cross-section for the 1064nm emission was determined using the emission spectra. The highest gain bandwidth (σ e ×Δλ P ) was determined to be 155.4 for the 0.79TeO2–0.15WO3–0.05CdO ternary glass composition, which could be more useful as promising material for the design and development of fiber amplifiers and lasers. [Copyright &y& Elsevier]

Abstract: A Sm:GGG crystal was grown by the Czochralski method. The absorption and emission spectra of Sm:GGG were measured at room temperature. According to the Judd–Ofelt theory, the intensity parameters Ω t (t=2, 4, 6), spontaneous transition probabilities, branching ratio and radiative lifetime of 4G5/2 state were calculated. The emission cross-sections of 567, 613, 662 and 710nm were estimated. The decay curve of the 613nm emission assigned to the 4G5/2→6H7/2 transition was measured and the fluorescence lifetime was also determined. [Copyright &y& Elsevier]

Abstract: Tm3+-doped and Tm3+/Yb3+-codoped TeO2–ZnO–Bi2O3 (TZB) glasses are prepared by melt-quenching method. The Judd-Ofelt intensity parameters (Ω t t =2, 4, 6), radiative transition rate, and radiative lifetime of Tm3+ are calculated based on the absorption spectra. The 1.8μm emission of the samples is investigated under 980nm laser excitation. The absorption, emission cross-sections, and gain coefficient of Tm3+:3F4 → 3H6 are calculated. The energy transfer processes of Yb3+–Yb3+ and Yb3+–Tm3+ are analyzed, the results show that the Yb3+ ions can transfer their energy to Tm3+ ions with large energy transfer coefficient, and a maximum efficiency of 79%. [Copyright &y& Elsevier]

Abstract: The spectroscopic properties of tellurite glasses of composition (in mol%) TNKNd: (70− x)TeO2–15Nb2O5–15K2O–xNd2O3 (x =0.1, 1.0, 1.5, 2.0 and 2.5) and TNLNd10: 69TeO2–15Nb2O5–15Li2O–1.0Nd2O3 and lithium metaborate glass of composition LBNNd10: 89LiBO2–10Nb2O5–1.0Nd2O3 have been investigated using absorption and emission spectra and decay curve analysis. An energy level analysis has been carried out considering the experimental energy positions of the absorption and emission bands, using the free-ion Hamiltonian model. The spectral intensities have been calculated by using the Judd–Ofelt theory and in turn the radiative properties such as radiative transition probabilities, emission cross-sections, branching ratios and radiative lifetimes have been estimated. The decay curves at the lower concentrations are exponential while they show a non-exponential behavior at higher concentrations (⩾1.0mol%) due to energy transfer processes. The effective lifetimes for the 4F3/2 level are found to decrease with increase in Nd2O3 concentration for all the glasses under investigation. The non-exponential decay curves have been well-fitted to the Yokota–Tanimoto model with S =6, indicating that the nature of energy transfer is of dipole–dipole type and energy migration also plays an important role. The results obtained have been compared with Nd3+-doped phosphate, fluorophosphate, lead borate, tellurite, germanate and silicate glasses and Nd3+-doped YAG ceramic and Ca2Nb2O7 crystals. [Copyright &y& Elsevier]

Abstract: This article reports the effect of mixed alkalis on the optical absorption and emission spectra of Sm3+ and Dy3+ doped chloroborate glass matrices of the compositions 69.5B2O3 xLiCl(30− x)NaCl0.5R2O3 and 69.5B2O3 xLiCl(30− x)KCl0.5R2O3 (where R=Sm and Dy and x =5, 10, 15, 20 and 25). Using Judd–Ofelt theory, the spectral intensities and Judd–Ofelt intensity parameters (Ω 2, Ω 4 and Ω 6) were obtained from the measured absorption bands of the spectra. Using these intensity parameters, total radiative transition probabilities (A T), radiative lifetimes (τ R), branching ratios (β) and peak emission cross-sections (σ P) were obtained for the two rare earth ions in these two glass matrices. Variation of these parameters with x in the glass matrix has been discussed. It is found that for Sm3+ ion, the transition, 4G5/2 → 6H9/2 shows highest emission cross-section and is maximum at x =10mol% in lithium–sodium and at x =20mol% in lithium–potassium glass matrices. For Dy3+ ion, the transition, 4F9/2 → 6H13/2 shows highest emission cross-section and is maximum at x =20mol% in lithium–sodium and at x =10mol% in lithium–potassium glass matrix. [Copyright &y& Elsevier]

Abstract: Nd3+ ions doped alkaline-earth titanium phosphate glasses were prepared by using the conventional melt quenching method. Absorption spectra were recorded and oscillator strengths of the transitions were calculated using area under the absorption bands. The energy level analysis was carried out by using free-ion Hamiltonian model. The three host dependent Judd–Ofelt intensity parameters, Ω λ (λ =2, 4, and 6) were used to elucidate the structure of glassy matrix around Nd3+ ion as well as to determine the 4F3/2 metastable state radiative properties such as radiative transition probabilities, branching ratios and radiative lifetimes. The decay curves of all the three glasses show single exponential behavior. The discrepancy between the experimental and calculated lifetimes of emitting level was attributed to multiphonon relaxation. The achieved high quantum efficiencies for the 4F3/2 level indicate efficient laser emission at 1.06μm in these glass systems. [ABSTRACT FROM AUTHOR]

Abstract: The room-temperature absorption spectrum, fluorescence spectra, and fluorescence decay curves of Pr3+-doped Gd3Ga5O12 single crystal were studied systematically. The standard and modified Judd–Ofelt theories were used to determine the Judd–Ofelt intensity parameters Ω t (t =2, 4, 6), radiative transition probabilities, radiative lifetimes and branching ratios. The stimulated emission cross-sections and the fluorescence quantum efficiency of the promising laser levels were calculated and discussed. The multi-exponential behavior of the fluorescence decay curve of the 1D2 → 3H4 transition was explained by using the Inokuti–Hirayama theory. The obtained spectroscopic results show the potential application of the Pr3+-doped Gd3Ga5O12 crystal as visible solid-state lasers. [Copyright &y& Elsevier]

Abstract: Spectroscopic characterization for optical amplification and laser application of the Er3+-doped Bi4Si3O12 glass is performed through its absorption and luminescence spectra. The spontaneous radiative transition probabilities from the first seven excited states to the ending states are calculated to obtain the luminescence branching ratios and radiative lifetimes. Intense infrared to visible luminescence of the Er3+ ion is observed with 4I9/2 state excitation (800nm) under a 200mW laser excitation power. The value obtained for the ratio of the 4I11/2 → 4F7/2 excited-state absorption oscillator strength to the 4I15/2 → 4I11/2 ground state absorption oscillator strength is in accordance with those reported for Er3+-doped materials pumped efficiently at 4I11/2 level excitation wavelengths. Gain cross-section spectra as a function of the inverted population rate and the stimulated emission cross-section spectrum were determined for the 4I13/2 → 4I15/2 infrared (IR) laser transition. The large gain bandwidth of the 4I13/2 → 4I15/2 IR emission has resulted in being close to those reported for Er3+-doped oxide glasses suitable for broadband amplifiers. [Copyright &y& Elsevier]

Abstract: Structural and spectroscopic properties of neodymium doped sodium borate and fluoroborate glasses of composition (in mol%) (99− X) B2O3 + XNa2O+1Nd2O3, X =49.5, 39.5 and 29.5 and 49.5B2O3 + XNa2O+(49.5− X) NaF+1Nd2O3, X =0 and 24.75 have been investigated using XRD, FTIR, absorption and emission spectra and decay curve. The XRD of the glasses confirm their glassy nature and the FTIR spectra reveal the presence of BO3 and BO4 units along with the strong OH− groups in the glasses. The UV–vis-NIR absorption spectra were used to calculate the bonding parameters ( and δ), to identify the ionic/covalent nature of the glasses. The spectral intensities have been calculated by using Judd–Ofelt analysis and inturn used to estimate radiative properties such as radiative transition probabilities, radiative lifetimes, branching ratios, peak stimulated emission cross-sections. Branching ratios and stimulated emission cross-sections show that the 4F3/2 → 4I11/2 transition of the glasses under investigation has the strong emission around 1060nm. The decay from the 4F3/2 level of Nd3+ ions is found to be single exponential. Multiphonon relaxation and quenching due to OH− groups play a governing role in the luminescence quenching of 4F3/2 level of Nd3+ ions in the titled glasses. The results obtained are compared with reports on similar glasses. [Copyright &y& Elsevier]

Abstract: Optical absorption and emission spectra of Pr3+ and Er3+ doped different chlorophosphate glasses have been studied. Optical properties of these two rare earth ions were characterized through optical absorption and emission spectra using Judd–Ofelt theory. Judd–Ofelt intensity parameters Ω λ (λ=2, 4 and 6) are calculated for both the ions from their absorption spectra, which in turn used to derive the radiative properties such as radiative transition probabilities (AT ), radiative lifetimes (τR ), branching ratios (β) and integrated absorption cross-sections (Σ). An attempt has been made to discuss structural changes considering the hypersensitive transitions and covalency of rare earth oxygen (RE-O) bonds for the present glass systems. From emission spectra, peak emission cross-sections (σP ) are obtained for the observed emission bands of Pr3+ and Er3+ ions in all these chlorophosphate glasses. Variation of peak emission cross-sections with the glass matrix has been studied. [Copyright &y& Elsevier]

Abstract: Nd3+-doped tellurite–germanate glasses with various compositions were prepared by a conventional melt-quenching method. On the basis of Judd–Ofelt theory, the optical transition intensity parameters Ωλ (λ=2, 4, 6) of Nd3+ in all the samples were calculated from the absorption spectra. By using these three intensity parameters, the radiative transition properties, such as the transition rates, branch ratios for 4F3/2→4I11/2 and 4F3/2→4I9/2 transitions, and radiative lifetimes of 4F3/2 level of Nd3+ in all the glasses were carefully calculated. The compositional dependence of these spectroscopic parameters was analyzed. According to the McCumber theory, the emission cross sections for 4F3/2→4I9/2 of Nd3+ in various glasses were obtained, furthermore the optical gain properties for 4F3/2→4I9/2 transition in all the samples were also studied. [Copyright &y& Elsevier]

Abstract: 53.3BiO1.5–33.3GeO2–13.4NaO0.5 (cation%) glasses with various Tm3+ concentration were prepared by melt-quenching method. These glasses show high density, high refractive index, low phonon energy and good stability against crystallization. Absorption spectra of Tm3+-doped bismuthate glass were measured to obtain the radiative lifetimes by Judd-Ofelt theory. The absorption (4.5×10−21 cm2) and emission (6.7×10−21 cm2) cross-sections were calculated by Beer–Lambert and McCumber theory. The results show that the Tm3+ (3F4 → 3H6) in these glasses have high spontaneous radiative transition probabilities and large stimulated emission cross-section. Then the fluorescence emission spectra were measured under 808nm excitation and the maximum emission intensity at 1.8μm is obtained at 0.9mol% Tm2O3 in the glasses. [Copyright &y& Elsevier]

Abstract: Praseodymium-doped borovanadate glasses were prepared by conventional quenching melt technique. The prepared composition was [90 Na2B4O7–(10− x)V2O5–x Pr6O11], x =0, 0.5, 1, 2, 4, 6, 8 and 10mol%. Optical absorption spectra have been investigated in the spectral range from 195 to 2500nm. Experimental oscillator strengths of the observed bands have been estimated and used for calculating the Judd–Ofelt (JO) intensity parameters. Radiative transition probabilities as well as branching ratios were calculated. The radiative lifetime of the 1D2 and 3P0 levels was varied from ca. 344 to 808μs and ca. 30 to 63μs respectively. The optimum Pr concentration at which the branching ratios have the maximum values was obtained at 1mol%. [Copyright &y& Elsevier]

Abstract: Optical absorption and emission spectra of Ho3+ doped alkali, mixed alkali and calcium phosphate glasses of the type (69.5NH4H2PO4·15Na2HPO4)·15R2CO3 (R=Li, Na and K), (69.5NH4H2PO4·15Na2HPO4)·7.5Li2CO3·7.5R2CO3 (R=Na and K), (69.5NH4H2PO4·15Na2HPO4)·7.5Na2CO3·7.5K2CO3 and (69.5NH4H2PO4·15Na2HPO4)·15CaCO3 have been studied. Variation of Judd–Ofelt intensity of parameters (Ωλ ), peak wavelengths of the hypersensitive transitions (λp ), radiative transition probabilities (A rad) and peak emission cross-sections (σp ) with the variation of alkalis, mixed alkalis and calcium in the phosphate glass matrix has been studied. The shift in peak wavelength of the hypersensitive transition and Judd–Ofelt intensity parameter (Ω 2) are correlated with the structural changes in the host matrix. Radiative lifetimes (τR ) are estimated for certain excited states of Ho3+ in these glass matrices. From the luminescence spectra, the emission cross-sections (σp ) are evaluated for the two emission transitions of Ho3+ ion. Variation of luminescence intensities of the two transitions, absorption and emission cross-sections with the variation of alkalies, mixed alkalies and calcium in the above phosphate glass systems has been studied. [Copyright &y& Elsevier]

Abstract: Tm3+ and Ho3+ co-doped TeO2–ZnO–Bi2O3 (TZB) glasses were prepared by the conventional melt-quenching method. Two micrometre emission properties of the TZB glasses exited by 808nm Laser Diode (LD) were analyzed and discussed. The Judd–Ofelt parameters, spontaneous radiative transition probabilities and radiative lifetime of Ho3+ were calculated based on the absorption spectra by using Judd–Ofelt theory. The absorption spectra and fluorescence spectra were measured. The predicted spontaneous radiative transition rate of 5I7 → 5I8 of Ho3+ is as high as 466.8 s−1. The result of fluorescence spectra indicates that the maximum emission intensity of Ho3+ 2.0μm and of Tm3+ 1.47μm emission can be achieved at the concentration of 1mol% Tm2O3 and 1mol% Ho2O3 in TZB glasses. The maximum absorption and emission cross-section of Ho3+ near 2.0μm are 0.87×10−20 cm2 at 1951nm and 1.07×10−20 cm2 at 2047nm, respectively. [Copyright &y& Elsevier]

Abstract: The fluorophosphate glasses with the composition (mol%) of (56− x)P2O5 +17K2O+(12− x)MgO+6MgF2 +9Al2O3 + xNd2O3 and (56− x)P2O5 +17K2O+(12− x)SrO+6SrF2 +9Al2O3 + xNd2O3 (where x =0.1, 1.0, and 2.0mol%) have been prepared and characterized by absorption and luminescence spectra and decay curve analysis. The absorption band positions of Nd3+ ions have been analyzed using the free-ion Hamiltonian model. From the absorption spectra, Judd–Ofelt intensity parameters have been evaluated which are in turn used to predict radiative properties such as total radiative transition probabilities, radiative lifetimes and branching ratios. The present glasses have high stimulated emission cross-sections, implying that they have potential for laser applications. Lifetime of the 4F3/2 level decreases with increasing Nd3+ ions concentration. The non-exponential decay curves have been fitted to the generalized Yokota and Tanimoto model and derived energy transfer and migration parameters, donor–acceptor coupling constants and diffusion coefficients. The free OH content in the 1.0mol% Nd2O3-doped glasses has been estimated from their measured Fourier transform infrared transmittance spectra. [Copyright &y& Elsevier]

Abstract: Net thermal radiation cooling, from surfaces at sub-ambient temperatures, to the night sky is amplified if the aperture to the sky is partially blocked with heat mirrors. The temperature at which radiation loss stagnates (the effective sky temperature) falls continuously as the aperture closes and is derived in terms of the aperture size and the spectral properties and temperatures of the atmosphere and of the emitting surface. Cooling surfaces must have high absorptance between 7.9μm and 13μm where the atmosphere is most transparent. The best response for the remainder of the Planck radiation spectrum surprisingly switches between two spectral extremes at a temperature which falls as the aperture gets smaller. A perfect absorber is best above this switch, while surfaces which reflect all of this radiation are best below it. A simple formula is presented for the cross-over temperature as a function of aperture size. With known material properties plus representative non-radiative heat gains a high emittance surface is generally better except when heat mirrors are not used. A known high emittance roof paint at 10°C below ambient, under a 45° aperture lined with shiny aluminium, can achieve a net output power near 135Wm−2 under a clear sky. [Copyright &y& Elsevier]

Abstract: Using both high resolution (0.0018cm−1) and medium resolution (0.112cm−1) Fourier transform spectra of an enriched 34S (95.3%) sample of sulfur dioxide, it has been possible to accurately measure a large number of individual line intensities for some of the strongest of the SO2 bands, i.e. ν 1, ν 3 and ν 1+ ν 3. These intensities were least-squares fitted using a theoretical model which takes into account the vibration–rotation interactions linking the upper energy levels where needed, and, in this way, expansions of the various transition moment operators were determined. The Hamiltonian parameters determined in previous analyses together with these moments were then used to generate synthetic spectra for the bands studied and their corresponding hot bands providing one with an extensive picture of the absorption spectrum of 34SO2 in the spectral domains, 8.7, 7.4, and 4μm. [Copyright &y& Elsevier]

Abstract: Lorentz air-broadened half widths, pressure-induced shifts and their temperature dependences have been measured for over 430 transitions (allowed and forbidden) in the ν 4 band of 12CH4 over the temperature range 210–314K. A multispectrum non linear least squares fitting technique was used to simultaneously fit a large number of high-resolution (0.006–0.01cm−1) absorption spectra of pure methane and mixtures of methane diluted with dry air. Line mixing was detected for pairs of A-, E-, and F-species transitions in the P- and R-branch manifolds and quantified using the off-diagonal relaxation matrix elements formalism. The measured parameters are compared to air- and N2-broadened values reported in the literature for the ν 4 and other bands. The dependence of the various spectral line parameters upon the tetrahedral symmetry species and rotational quantum numbers of the transitions is discussed. All data used in the present work were recorded using the McMath–Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak. [Copyright &y& Elsevier]

Abstract: All available transitions from microwave to visible region (0.2–12 105cm−1) of the HD18O molecule were collected and tested using the RITZ computer code. Literature data were completed by transitions assigned to HD18O in long path Fourier transform absorption spectra of the H2O, HDO and D2O gas mixtures with natural abundance of oxygen-18. In addition about 40 unassigned lines between 4200 and 6600cm−1 of our previous water study associated with the HD18O molecule have been found and assigned. The new long path absorption spectra of the HDO and D2O mixtures allow us to observe about 1000 transitions of HD18O in the 6125–10720cm−1 spectral region. These data have been critically analyzed and used to obtain the most complete and precise set of the experimental energy levels of this molecule. [Copyright &y& Elsevier]

Abstract: Spectroscopic investigations were performed on 68NH4H2PO4·xLi2CO3(30− x)K2CO3 and 68NH4H2PO4·xNa2CO3(30− x)K2CO3 (where x =5, 10, 15, 20 and 25) glasses containing 2mol% Nd2O3. Various spectroscopic parameters (Racah (E1, E2, E3), spin–orbit (ξ4f) and configuration interaction (α)) are reported. Judd–Ofelt intensity parameters (Ω 2, Ω 4, Ω 6) are calculated for Nd3+ doped two mixed alkali phosphate glass matrices. From the magnitude of Judd–Ofelt parameters, covalency is studied as a function of x in the glass matrix. Using Judd–Ofelt intensity parameters, total radiative transition probabilities (A T), radiative lifetimes (τ R), branching ratios (β) and integrated absorption cross sections (Σ) have been computed for certain excited states of Nd3+ in these mixed alkali phosphate glasses. Emission cross sections (σ P) are calculated for the two transitions, 4G7/2 → 4I11/2 and 4G7/2 → 4I13/2 of Nd3+ in these mixed alkali phosphate glasses. Optical band gaps (E opt) for direct and indirect transitions are reported. [Copyright &y& Elsevier]

In the present study the various spectroscopic parameters of the triply ionized holmium (Ho3+) doped TeO 2 –Pb 3 O 4 (TPO) glass fabricated through melting and quenching technique have been investigated by using the Judd-Ofelt (J-O) analysis. The determined higher Judd-Ofelt intensity parameter Ω 2 signifies the existing covalent bonding. The transition 5S 2 +5F 4 →5I 8 corresponding to the peaked energy at 18552.9 cm−1 shows the largest radiative transition probability (3315.5 s−1) and gives the confirmation for the observed strong green emission in the Upconversion (UC) study. The UC spectroscopy of the Ho3+/Yb3+ ions doped and codoped TPO glasses upon 980 nm CW laser excitation have been analyzed. The effect on the UC luminescence intensity of Ho3+: TPO glass in the presence of Yb3+ ions has been studied and the intensity enhancement processes are explored. On the basis of present investigations, the Ho3+/Yb3+ codoped TPO glass can be utilized as good optical upconverter and yellowish green display devices. [Display omitted] • Frequency upconversion (UC) emission and absorption spectra have been performed for Ho3+/Yb3+ doped and codoped TPO glasses. • UC luminescence of Ho3+: TPO glass in the presence of Yb3+ ions was studied & intensity enhancement processes are explored. • The colour coordinate of the emitted colour from the Ho3+-Yb3+: TPO glass upon NIR excitations is reported. • The UC emission has also been explained by Judd-Ofelt analysis. • Developed glass exhibit promising applications in NIR to visible upconverter & non-colour tunable yellowish green optical devices. [ABSTRACT FROM AUTHOR]

Abstract: The discrete ordinates interpolation method (DOIM) is applied to three groups of problems of radiative heat transfer in three-dimensional rectangular enclosures containing non-gray or scattering medium. The original DOIM is first extended to a gray gas model using a new geometric interpolation scheme. It is applied to participating media for different scattering phase functions and optical thicknesses. For the non-gray gas model, the DOIM coupled with the narrow band-based weighted-sum-of-gray-gases (WSGG) model is developed. A few test problems with real gases such as pure H2O and a mixture of CO2, H2O and N2 are taken. The wall heat flux is calculated and compared with the exact solutions or reference values. All results of test problems are found to be reliable in this study. The DOIM closely reproduces the Monte Carlo reference solutions for different scattering phase functions and optical thicknesses. The non-gray gas results are compared with reference calculations based on the statistical narrow band model and they also show good agreements. The DOIM shows a remarkable merit in the computation time and the grid compatibility, to prove its usefulness for engineering applications. [Copyright &y& Elsevier]

Abstract: The absorption spectrum of H2O has been extensively studied over the past decades in the near-infrared and visible regions, but there remain significant discrepancies in the 10,000–12,500cm−1 range even for the most intense lines. We have studied 24 lines of H2O using an external-cavity diode laser emitting in the 810–830nm range, in order to measure absolute line intensities as well as air- and self-broadening coefficients. Comparisons were made with values obtained from the HITRAN database and also with other parameters from recent experiments or predicted calculations. It is suggested that neglecting the effects of H2O collisional narrowing in radiative transfer calculations of the Earth''s atmosphere may have a small but significant impact on the radiative budget of the Earth. [Copyright &y& Elsevier]

Na0.4Y0.6F2.2:Tm3+ crystals with a thulium content from 1 to 100 at % have been grown by the Stockbarger-Bridgman method. The optical spectra of Na0.4Y0.6F2.2:Tm3+ crystals were investigated in detail at room and low (10 K) temperatures, and the luminescence kinetics was analyzed using different excitation methods. The structure of the Stark splitting of thulium levels as “quasi-centers,” characterized by inhomogeneous broadening of the Stark components, is determined from analysis of the absorption spectrum at 10 K. The oscillator strengths of the transitions from the ground state to excited multiplets are determined from the absorption cross-section spectra at 300 K for ten transitions in the range 5000–38 500 cm−1 and seven transitions in the range 5000–28 500 cm−1. The transition intensity parameters Ω t , obtained by the Judd-Ofelt method from the spectra due to the transitions to ten and seven excited levels, were found to be, respectively, (i) Ω2 = 1.89 × 10−20, Ω4 = 2.16 × 10−20, and Ω6 = 1.40 × 10−20 cm2 and (ii) Ω2 = 2.04 × 10−20, Ω4 = 2.01 × 10−20, and Ω6 = 1.44 × 10−20 cm2. These values of the intensity parameters were used to calculate the radiative transition probabilities and branching ratios and to estimate the multiphonon nonradiative transition probabilities for NYF:Tm. The luminescence decay kinetics from thulium radiative levels upon their selective excitation by nanosecond laser pulses has been studied and the lifetimes of thulium radiative levels in NYF crystals have been found. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the optical properties of Dy3+ in sodium fluoroborate glasses of the type XNaF·(89− X)B2O3·10 Al2O3·1Dy2O3 (where X =8, 12, 16, 20 and 24). Judd–Ofelt intensity parameters (Ω 2, Ω 4, Ω 6) are derived from the absorption spectra. The Judd–Ofelt theory has been applied to interpret the local environment of Dy3+ ions and bond covalency of RE–O bond. These parameters have been used to calculate radiative transition probabilities (A rad), lifetimes (τ R) and branching ratios (β R) for the excited level 4F9/2. The predicted values of τ R are compared with the measured values for 4F9/2 level for five glass compositions (Glass (A–E)). The stimulated emission cross-section σ(λ P) are also evaluated for the 4F9/2 → 6H J (J =11/2, 13/2, and 15/2) transitions. [Copyright &y& Elsevier]

Abstract: Nd3+-doped NaLa(WO4)2 single crystal with a dimension of ∅20mm×40mm and a good optical quality was grown by Czochralski method. The polarized absorption spectra and emission spectra were measured at room temperature. The absorption cross-section and emission cross-section were presented. The Judd–Ofelt theory, extended to anisotropic system, has been applied to evaluate the intensity parameters Ω t (t =2,4,6), radiative transition rates A, radiative lifetimes τ R and fluorescent branching ratios β. The calculated radiative lifetime was compared with the experiment data for the 4F3/2 emitting level. All spectral features are strongly affected by an inhomogeneous broadening connected with the ‘disordered crystal’ character of the title compound. [Copyright &y& Elsevier]

Abstract: This article presents the optical absorption and emission properties of Eu3+ in sodium fluoroborate glasses of the type XNaF·(89–X)B2O3·10Al2O3·1Eu2O3 (where X=8, 12, 16, 20, and 24). Judd–Ofelt (JO) intensity parameters (Ω 2, Ω 4, Ω 6) are derived from the absorption spectra. These parameters have been used to calculate radiative transition probabilities (A rad), lifetimes (τ R) and branching ratios (β R) for the excited level 5D0. The predicted values of τ R are compared with the measured values for 5D0 level for five glass compositions (Glass (A–E)). The stimulated emission cross section σ(λ P) are also evaluated for the 5D0→7F J (J=0,1,2,3,4) transitions. [Copyright &y& Elsevier]

Based on the analysis of the absorption spectra of Er-doped calcium-niobium-gallium garnet (Er:CNGG) crystals according to the Judd-Ofelt theory, the intensity parameters for these crystals are determined to be Θ2 = 3.43 × 10−20 cm2 Θ4 = 1.20 × 10−20 cm2, and Θ6 = 0.58 × 10−20 cm2. The parameters found are compared with the intensity parameters for other laser oxide crystals. Using these intensity parameters, the probabilities of radiative transitions between the energy levels of Er3+ ions in CNGG crystals and the luminescence branching ratios βJJ’ are calculated. From the measured lifetime of the 4 I 11/2 level of Er3+ ions (τ = 626 μs) and the probability of the radiative transition from this level ( A = 192 s−1), it is found that about 88% of the excitation energy in the Er:CNGG crystals is nonradiatively transferred from the 4 I 11/2 to the 4 I 13/2 level. It is suggested that an increase in the oscillator strength and in the line strength of the 4 I 15/2 → 2 H 11/2 transition of Er3+ in CNGG crystals, as well as an increase in the intensity parameter Θ2 with respect to the corresponding parameters for other garnet crystals are caused by the existence in CNGG crystals of Er3+ centers with the environment symmetry lower than D 2. [ABSTRACT FROM AUTHOR]

A Tm3+-doped NaLa(WO4)2 single crystal with a dimension of Φ20 mm×40 mm was grown by the Czochralski method. Anisotropic thermal expansion coefficients of this crystal were investigated. Polarized absorption spectra, emission spectra and decay curve were recorded at room temperature. The absorption and emission cross-section were presented. Based on the Judd–Ofelt analysis, we obtained the three intensity parameters: Ω2=10.21×10-20, Ω4=2.66×10-20, and Ω6=1.46×10-20 cm2. The radiative probabilities, radiative lifetimes, and branch ratios of Tm3+:NaLa(WO4)2 were calculated, too. Luminescence lifetime of the 3 H 4 level was measured to be 220 μs. The stimulated emission cross-section for the 3 F 4→3 H 6 transition were determined using the reciprocity method, potential laser gain for this transition were also investigated, the gain curves implied that the tunable range is up to 200 nm. [ABSTRACT FROM AUTHOR]