Intensity Parameters Ω2 Research Articles

Studies on a novel Ho3+:KBGM crystal toward the ∼2 μm laser applications

A Ho3+:KBGM crystal with good quality and large size was successfully grown via TSSG method. The crystal’s structure, ambient-temperature polarized absorption and emission spectra and fluorescence lifetime were studied. The J-O theory was adopted to analyze the absorption spectra and results show that crystal exhibits relatively large intensity parameters Ω2 and spectroscopic quality factor which is up to 3.12. At 453 nm, the absorption band is the strongest, and the corresponding cross-sections are 21.94 × 10–20 cm2, 26.66 × 10–20 cm2 and 18.56 × 10–20 cm2 for the -X, -Y and -Z polarizations, respectively. The emission spectra also demonstrate the broad and strong emission band at 2030 nm. The FWHMs and cross-sections are 74 nm, 0.37 × 10−20 cm2, 50 nm, 0.68 × 10−20 cm2, and 49 nm 0.52 × 10−20 cm2 for the three polarizations, respectively. In addition, the crystal has a superior quantum efficiency which is as high as 97.1%. Taking all the analyses into account, it is reasonable to assert that the Ho3+:KBGM crystal an ideal candidate for ∼2 µm laser applications in many areas.

Optical and luminescence studies of Nd3+ doped phosphate glasses for pulsed laser applications

A series of glass with appropriate chemical compositions (60-x) P2O5 + 20 Bi2O3 + 10 SrF2 + 10 Na2 CO3 + x Nd2O3, (x = 0.1, 0.5, 1.0, 1.5, and 2.0% by mole) were prepared by using the melt quenching technique. The glass phase structure was confirmed by using X-ray diffraction technique. The structural analysis using FTIR technique it reveals characteristic bonding vibrations and different functional group in the glass matrix. The elements present in the fabricated glass sample was analyzed by using EADX spectrum. J-O intensity parameters Ω2, Ω4, and Ω6for the currently being researched PBNSNd10 glass have values of 9.80 × 10-20 cm2, 3.305 × 10-20 cm2, and 5.576 × 10-20 cm2 sequentially. The J-O parameters shows a trend of Ω2 > Ω6 > Ω4. The near infrared emission spectra recorded with 808 nm laser diode excitation for various concentrations of neodymium ions show the emission intensity is highest for the 4F3/2 → 4I11/2 transition at 1056 nm. The measured decay times 4F3/2 level decreased with increasing Nd2O3 ions because of concentration quenching effect. The obtained results in present study have been compared with previous results obtained for Nd2O3 doped glasses.

NIR emissions from Nd3+-activated phosphate-based glass system for cost-effective, tunable, and miniaturised laser devices

This work represents a phosphate-based glass system of composition (40-x) P2O5 − 30 B2O3 − 30 ZnSO4 - x Nd2O3, ( × = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) to determine the optical absorption and emission spectral characteristics. Moreover, Judd-Ofelt (J-O) intensity and radiative parameters were computed. Samples were prepared using melt-quenching method and characterized using Archimedes measurement, Ultraviolet–Visible-Near Infrared Spectroscopy and Photoluminescence Spectroscopy. The density values of these samples were reduced as the Nd2O3 concentration increased. The absorption spectra revealed 11 peaks corresponded to Nd3+ transitions from the lowest electronic energy level (4I9/2) to various excited levels. The optical energy band gap was found to be reduced with Nd3+ doping. The refractive indices (n) increased as the Nd3+ increase. The improving tendency of n was clarified in terms of the enhancing trend of samples molar volume (obtained from density), indicating a structural-optical correlation in the proposed glass system. The obtained values of Urbach energy (Eu) have an increasing trend in the range of ∼ 0.318–0.711 eV. Tow significant NIR emission peaks were assigned to the 4F5/2 → 4I9/2 and 4F3/2 → 4I9/2 transitions of Nd3+. Values of J-O intensity parameters Ω2, Ω4 and Ω6 were found in the range of (1.63–2.25)× 10−19 cm2, (2.57–2.94)× 10−19 cm2 and (1.53–1.82)× 10−19 cm2, respectively. The obtained stimulated emission cross-section for the NIR transitions from Nd3+ ((23.83–26.64)× 10−20 cm2 for 4F5/2 → 4I9/2, and (10.93–17.91)× 10−20 cm2 for 4F3/2 → 4I9/2 obviously revealed the lasing effectiveness of the titled glass system.

Enhanced emission intensity in (Li+/Ca2+/Bi3+) ions co-doped NaLa(MoO4)2: Dy3+phosphors and their Judd-Ofelt analysis for WLEDs applications

In the present study, we have synthesized a series of Dy3+ ion doped NaLa(MoO4)2phosphors by the conventional solid-state method at 750 °C for 4h. All the compounds were crystallized in the tetragonal scheelite type structure with space group (I41/a, No.88). The morphology and functional group were confirmed by the field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared(FTIR)spectroscopy. Upon near-Ultraviolet (n-UV) excitation, the PL spectra exhibit the two characteristic emissions of Dy3+ ions, blue (4F9/2 → 6H15/2) at 487 nm and yellow (4F9/2 → 6H13/2) at 574nm respectively. The optimum concentration of Dy3+ionis 3 mol% and then quenching occurred due to multipolar interaction. Further, enhanced the emission intensity by co-doping with monovalent (Li+), divalent (Ca2+) and trivalent (Bi3+) ions. Among them, Li+ ion co-doped samples are shown maximum intensity (50 times) more than Dy3+ doped phosphors as relaxation of parity restriction of electric dipole transition because of local distortion of crystal field around the Dy3+ ions. In addition, by incorporation of Eu3+ ions into NaLa(MoO4)2:Dy3+system, tuned the emission color from white to red, owing to energy transfer from Dy3+ to Eu3+ ions. The intensity parameters (Ω2, Ω4) and radiative properties such as transition probabilities (A T), radiative lifetime (τ rad), and branching ratio were calculated using the Judd-Ofelt theory. CIE color coordinates, CCT values indicates that these phosphors exhibit an excellent white emission. The determined radiative properties, CIE and CCT results revealed that the Dy3+-activated NaLa(MoO4)2phosphors are potential materials for developing white LEDs, and optoelectronic device fabrications.

Synthesis and photo-physics of luminescent Sm(III) complexes derived from β-hydroxyketone and heterocyclic ancillary ligands

A series of six Sm (III) complexes containing organic ligands were synthesized using liquid assisted environment-friendly grinding method. The complexes were characterized through various techniques like UV, IR, NMR, XRD, SEM, EDAX, PL and TGA/DTG. The luminescent properties studies in solid and solution form suggests that 4G5/2 → 6H7/2 (604 nm) and 4G5/2 → 6H9/2 (645 nm) transitions were accountable for the orange and reddish orange emission respectively on UV excitation. An orange colour light emission is also consistent with the outcomes of chromaticity, i.e., colour coordinates, CCT, and CP. To know further about the coordination environment Judd-Ofelt intensity parameters (Ω2, Ω4, Ω6) were calculated. In complexes greater value of Ω2 in comparison to Ω4 and Ω6 is the result of greater covalence. The band gap and Urbach energy obtained lie in the range of semiconductor devices. The HOMO-LUMO gap obtained theoretically and experimentally are in agreement with each other. These complexes have potential application in laser devices. The evaluation of antioxidant and antimicrobial properties of complexes indicates their application in pharmaceutical industry.

Enhanced Emission of Tellurite Glass Doped with Pr3+/Ho3+ and Their Applications.

The shielding and spectroscopic properties of Pr+3 and Pr3+/Ho3+-codoped tellurite glass were investigated. The intensity parameters (Ω2 = 3.24-, Ω4 = 1.64-, Ω6 = 1.10 × 10-20 cm2) as well as the radiative lifetimes of 3F4 + 5S2 and 5I6 excited states of Ho3+ ions were equal to 301 μs and 3.0 μs, respectively. The former value appears to be much higher than that obtained from the lifetime measurement, indicating the presence of various energy transfer processes. The NIR spectrum of Pr3+/Ho3+-co-doped tellurite glass is dominated by strong Ho3+: 5I6 emission at around 1200 nm, being the result of the energy transfer from Pr3+ to Ho3+ ions. The shielding effectiveness of the prepared glasses showed good performance against high-energy photons. These findings suggest that the prepared glasses could be used in laser technology such as photodynamic therapy (PDT) treatment procedures and as shielding for radiation protection.

Optical, emission, and excitation dynamics of Eu3+ -doped bismuth-based phosphate glass for visible display laser applications.

Eu3+ -doped-bismuth-based phosphate glasses with chemical equation (60 - x)P2 O5 -20Bi2 O3 -10Na2 CO3 -10SrF2 -xEu2 O3 (PBNSEu), (where x= 0, 0.1, 0.5, 1.0, 1.5 and 2mol%) were fabricated using the melt-quenching method. Obtain X-ray diffraction (XRD), energy-dispersive X-ray (EDAX), and Fourier transform infrared (FTIR) spectra were used to characterize the structure of the prepared PBNSEu glass. The J-O (Judd-Ofelt) intensity parameters (Ω2 , Ω4 ) were estimated using photoluminescence emission spectra. When excited with a xenon lamp at λexc = 394 nm, the most intense red-emission transition occurred at ~612 nm (5 D0 →7 F2 ). J-O intensity parameters were used to calculate radiative properties, whereas the radiative branching ratio (βR ), radiative transition probability (AR ), radiative lifetime (τR ), and total radiative transition rate (Aτ ) were calculated for the transitions 5 D0 →7 FJ (where J = 0-4) and were obtained in the emission spectra for europium ion-doped in the current glass. Using the CIE1931 chromaticity coordinates axes, the colours of various concentrations of Eu3+ ion-doped PBNS glass were evaluated using the emission spectra. Temperature-dependent luminescence spectra were recorded for the optimized PBNSEu20 glass to calculate the activation energy. These results strongly suggested red components in w-LEDs and visible display laser applications.

Concentration dependent Dy3+- doped lithium fluoro borotellurophosphate glasses’ structural and optical investigations for white light emission under UV excitation for solid-state lighting applications

Concentration dependent Dy3+ - doped lithium fluoro borotellurophosphate glasses were prepared by conventional melt quenching technique by varying the dopant concentration (0.1, 0.25, 0.5, 1.0 & 1.5 wt %). The structural and compositional analyses have been carried out through XRD, FTIR, SEM and EDAX respectively. The optical studies were made to analysis the optical behavior of the Dy3+ ions in the synthesized glasses through absorption and emission spectra. The nephelauxetic ratio and bonding parameter were calculated from the absorption spectra. The oscillator strength fexp and fcal along with σrms were evaluated and reported. The JO intensity parameters (Ω2, Ω4 and Ω6) have been calculated and trends reported. The photoluminescence spectra were recorded under 384 nm excitation. The radiative properties like emission band position (λp), effective bandwidth (Δλeff), radiative transition probability (A), stimulated emission cross-section (σpE), calculated and experimental branching ratios (βR) for the Dy3+-doped lithium fluoro borotellurophosphate glasses were calculated using JO intensity parameters and emission data. The CIE color coordinates (x,y) and Y/B ratio values were calculated from the photoluminescence spectra. The color correlated temperature (CCT) were determined from the (x,y) values and possibility for white light emissions from the synthesized glasses were analyzed under UV excitation. The decay analysis shows the non-exponential behavior of the present glasses.

Growth process of Yb, Er: Na0.04K0.96Y(WO4)2 crystals and luminescence properties in the near infrared range

The top seed solution growth (TSSG) method was used to grow the x mol% Yb, 5 mol%Er: Na0.04K0.96Y(WO4)2(x = 1, 3, 5, 7) (Yb, Er: NKYW) crystals. The structure and physical properties of the crystals were investigated using TG-DTA and X-ray diffraction (XRD) characterization. The absorption and luminescence intensities of crystals doped with various concentrations of rare earth ions were studied. Inside the crystal, the luminescence mechanism is based on Yb3+ ions as the sensitizer and Er3+ ions as the activator. The x mol% Yb, 5 mol%Er: NKYW (x = 1, 3, 5, 7) crystal spectral intensity parameters Ω2, Ω4, and Ω6 were calculated using the Judd-Ofelt theory. The absorption cross section, emission cross section, and gain cross section assisted analysis concluded that the 3 mol% Yb, 5 mol%Er: NKYW crystal has high laser emission potential. This research helps to advance the development of high- performance laser materials.

Nd3+ doped [formula omitted] glass systems: Structural and optical properties

The structural and optical characteristic features of B2O3 + Li2O + CaO + CaF2 (BLCofNd) glasses incorporated with Nd3+ as a dopant of different concentrations (mol%) are reported. The X-ray diffraction technique was used to study structural characteristics such as the amorphous nature of BLCOFNd glass samples, Infrared spectroscopy was used to investigate the presence of functional groups and their impact on optical characteristics (FTIR), It reveals the creation of a network by borate and other components with the characteristics of glasses demonstrating different stretching and oscillating behavior of borate functional groups. The recorded UV Vis-NIR spectra of BLCofNd glasses reveal the prepared glasses have strong absorption at 584 nm in the visible region and 805 nm in the NIR region for the transitions 4I9/2→4G5/2 and 4I9/2→4F5/2, these transitions are due to the excitation of electrons by induced absorption. The density (gm/cc) measurements seem to be a rise in the values with a proportionality increase in CaO concentration (mol%), which directly relates to the decrease in the interionic distance (ri) making the glasses optically dense. Judd–Ofelt intensity parameters (Ω2, Ω4 and Ω6) highlights a covalency symmetry with a higher degree and surrounding lattice distribution of Nd3+ ions with other glass elements present in the network. The radiative properties of BLCOFNd glass samples mainly relate to parameters of radiative transition probability (AR), and corresponding branching ratios (βcal and βrad), which are derived from oscillator strength (fexp) measurements, FWHM or peak bandwidth (Δλp), stimulated emission cross-section and gain bandwidth (σse. Δλp) foresees that BLCofNd glasses are best candidates for laser host materials. The neodymium-doped borate glass exhibits a high peak power due to its emission at 1.049 μm wavelength and has its applications as lasing material and is prominently used as a source to produce the secondary waves in the measurement of pollutants in the atmosphere, optical amplifiers, and in the industry for their high intensity in emitted radiation.

Concentration quenching effect on luminescent properties of Sm3+ ions doped ZnBiNaPSr glasses for photonic device applications

Concentration variation of trivalent samarium (Sm3+) ions doped ZnBiNaPSr oxyfluoride glasses have been prepared by using the standard melt quenching technique. The spectroscopic properties were investigated with diffraction, surface morphology, structural, optical and luminescence studies. The glassy nature of the samples was observed by the XRD pattern. The morphological images with feasible irregularities and elemental mapping were observed by SEM with EDS. The various structural PO, P–O–P, O–P–O and P–O–H phosphate bonds along with OH− groups were obtained by FTIR spectroscopy. The obtained absorption spectra in the UV–Vis–NIR region (300–1700 nm) consist of a series of bands assigned to respective transitions. The tauc's plots were drawn to estimate the band gap energies for the direct and indirect allowed transitions and measured the Urbach energy. The oscillatory strengths (fcal and fexp) and bonding parameters (δ) of each f-f transition have been evaluated. The phenomenological intensity parameters (Ω2, Ω4 and Ω6) were estimated from the J-O theory. The radiative parameters such as AT, τ, βR, Δλeff and σ were evaluated from the emission transitions. The luminescence intensity quenching was observed for the higher concentrations (1.5 & 2.0 mol%) of samarium ion. The high intense transition 4G5/2 → 6H7/2 (598 nm) was observed to be most suitable for the intense red-orange emission. The color coordinates, CCT, color purity of the ZnBiNaPSr oxyfluoride glasses were obtained from the CIE 1931 diagram.

Synthesis and properties of novel Pb/La/WO4: Eu3+ red phosphors for white light emitting diodes (WLEDs)

A novel red emitting phosphor PbLa2–2xEu2xW4O16(0 ≤ x ≤ 1) was successfully synthesized via solid-state method. Structure and crystallite size were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Excitation transmission and photoluminescence (PL) properties of the samples have been studied. The prepared red phosphor of PbLa1.13Eu0.88W4O16 demonstrated the highest red luminescence compatible with electronic transition 5D0→7F2 at 615 nm during the excitation by Light-emitting diode (LED) with a wavelength of 460 nm which corresponds to the excitation band 7F0→5D2. Moreover, the intensity parameters Ω2,4 and the quantum efficiency of the PbLa1.13Eu0.88W4O16 were calculated based on the Judd-Ofelt’s theory. We compared the PL properties of our prepared red phosphors with the compound of BaGd1.3Eu0.7(MoO4)4. Such comparison is a clear evidence of the superior efficiency of our prepared red phosphors for several applications related to the White Light Emitting Diodes (WLEDs).

Optical and radiation shielding properties of Sm3+ ions embedded bismuth-based fluorophosphate glasses for γ-ray shielding and multi-band visible laser applications

Bismuth based fluorophosphate (PBNS) glasses doped with samarium ions were fabricated by well-known melt quenching method. The structural, optical and fluorescence properties of PBNS glasses, were extensively investigated via XRD, FTIR, EDAX, optical absorption and fluorescence emission along with lifetime decay analysis. The intensity parameters (Ω2, Ω4, Ω6) were calculated using the Judd – Ofelt hypothesis, which follows the Ω4 > Ω6 >Ω2 trend. PBNSSm glasses doped with 1.0 mol% samarium ions (PBNSSm10) had a greater emission peak intensity than the produced glasses according to the emission spectra. The 4G5/2 → 6H7/2 transition emitting the radiation at 597 nm was more intense than the other transitions and got higher values for optical gain bandwidth (10.70 x 10−25 cm3), stimulated emission cross-section (10.05 x 10−20 cm2) branching ratio (0.48), and optical gain parameter (28.65 x 10−25 cm2s). The emission spectral results have been used to evaluate the colorimetric analysis of the 1931 CIE coordinates, and CCT values fall in the visible spectrum region. Moreover, the degree of protection of the synthesized PBNS glasses against gamma radiation was also evaluated. The obtained results suggested that the PBNS glass doped with 1.0 Sm3+ ions could be useful for multi-band visible laser applications. It was also concluded that 2.0% Sm3+ addition effectively increases the gamma-ray shielding properties of PBNS glasses, and therefore PBNSSm20 can be an alternative shielding material.

Spectroscopic properties and crystal-field effects in Er3+-doped tellurite and phosphate glass-ceramics

A series of Er3+-doped 40NaPO3–40KH2PO4-10ZnCl2-10Al2O3 (Er:NKZACl, 2Er:NKZACl) and 65TeO2-20ZnO-10BaO-3La2O3 (Er:TZBO) glasses were prepared by conventional melt quenching method, in order to compare and select the best chemical composition of glasses which exhibit opimal spectroscopic properties for broadband 1.54 µm laser emission and optical amplification. The samples were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), electron probe microanalysis with wavelength dispersion spectroscopy (EPMA/WDS), energy dispersive spectroscopy (EDS) and optical spectroscopy. Judd-Ofelt analysis was performed from the absorption spectra. The line strengths (Sexp and Scal) of different transitions between the 4I15/2 ground state and 11 excited states, as well as the Judd-Ofelt intensity parameters (Ω2,Ω4,Ω6) were calculated and compared to those of other glasses. Using these parameters, transition probabilities A, branching ratios β, radiative lifetimes τrad were determined. The experimental crystal-field energy sublevels of Er3+ cations were identified from the emission spectra at 77 K and the corresponding crystal-field parameters were refined for the 1Er:NKZACl and 2Er:TZBO glasses, by means of a crystal-field Hamiltonian endowed with C2 symmetry. In our study, the composition TZBO:Er3+ (2 mol%) exhibits optimal values of 4I15/2multiplet crystal-field splitting (383.7 cm−1), high Er3+ emission cross section at 1.54 µm (σem≃7.80 ×10−21 cm2), average experimental lifetime (2.97 ms) and high quantum efficiency (η≃85.6%) of the 4I13/2→4I15/2 emission. The obtained results make this glass a promising candidate for laser application and optical amplification in the infrared spectral range.

Photoluminescence of Y3NbO7:Eu3+ powders

Y3NbO7:xEu3+ powders (x = 0.25, 0.5, 0.75, 2, 3, 5, 10 at%) were synthesized by a two-step vibrational milling, alternating with annealing. All the samples crystallize as fluorite-type structure (space group Fm3‾m), with crystallite size 50–60 nm and show a strong orange/red luminescence with an excited state lifetime around 1.2 ms. Photoluminescence excitation and emission spectra show rapid intensity decline after 3 at% of Eu3+ content, indicating this concentration as critical for the concentration quenching, and we predicted multipolar interaction as the dominant mechanism behind it. Judd–Ofelt intensity parameters (Ω2 = 0.941∙10−20 cm2, Ω4 = 0.277∙10−20 cm2, Ω6 = 0.277∙10−20 cm2) were obtained from the excitation spectrum of Y3NbO7:3 at%Eu3+. The emission of this luminescent powder is characterized by radiative and nonradiative lifetimes of 2.3 ms and 2.4 ms, respectively, and an intrinsic quantum yield of 51.5%.

Spectroscopic properties of Nd3+ ions in Li2O[sbnd]MO (M=Mg, Ca and Sr)[sbnd]Sb2O3 glasses

The primary objective of the present work is to study the spectroscopic properties of Nd3+ ions in Li2OMO (M=Mg, Ca and Sr)Sb2O3 glass system. The current glass samples have been synthesized by the melt-quenching technique. The physical and thermal properties of the prepared glass samples have been calculated. Optical absorption, IR, photoluminescence (PL) and decay characteristics were recorded at ambient temperature. The Judd–Ofelt (J-O) intensity parameters Ω2, Ω4 and Ω6 for Nd2O3 mixed glasses were calculated using absorbance spectra and found to be the order Ω2 > Ω6 > Ω4. The SrO mixed glass sample J-O parameter Ω2 is found to be the lowest and has the highest emission intensity, radiative probability (A) and branching ratio (β) compared to other two glass samples MgO and CaO. The lifetime of 4F3/2 transition has been experimentally recorded at λexc= 585 nm and found that SrO mixed glass is a favorable one and getting the highest quantum efficiency (η = 64.5%). The chromaticity coordinates confirmed that the prepared glass samples were potential under 585 nm excitation wavelength. The IR studies suggest that the structural disorder may reduce the low phonon losses and increase the PL output in SrO mixed glasses. The studied results may useful for enhancing optical amplification as well as potential to generate in solid state NIR laser applications at 1.066 µm.

Judd-Ofelt, optical and photophysical analysis of β-ketocarboxylate Sm(III) complexes with N-donor aromatic system as secondary sensitizers

Reddish orange, Sm(III) complexes were synthesised by means of environmentally sustainable grinding method with β-keto carboxylic acid and heterocyclic aromatic systems. The photoluminescent studies revealed that 4G5/2 → 6H7/2 transition (608 nm) is responsible for the reddish orange emission of complexes when irradiated with UV light. Judd-Ofelt theory was applied to NIR absorption spectra to obtain three intensity parameters (Ω2, Ω4, Ω6) from oscillator strength. The higher Ω2 values obtained in complexes indicate greater covalence character. To assess luminescence performance, the radiative, nonradiative transition probability, radiative life time and intrinsic quantum yield were also evaluated. High quantum yield obtained for complexes signalises the superior luminescent behaviour. Exquisite color purity (89.8–96.2%) and CCT <3200 K establish these complexes as warm orange light source. The experimental data of absorption coefficient was fitted nonlinearly with Tauc's relation to obtain band gap energy. Two band gaps were reported in each complex hence the synthesised complexes can have materiality in solar cell and photovoltaic devices. The Urbach band tail width was also obtained through fitting with a new empirical relation which affirms the semiconducting properties of complexes. The investigation of antimicrobial and antioxidant properties of complexes ascertained the complexes as potent antibacterial and antioxidant agents.

Photoluminescent complexes of Eu(III), Tb(III) and Gd(III) with 3-thiopheneacetate and 4,4′-dimethyl-2,2′-bipyridine: Synthesis, characterization and photophysical properties

Three crystals of lanthanide complexes with 3-thiophenoacetic acid (3-HTAA) and 4,4′-dimethyl-2,2′-bipyridine (dmbpy) ligands were synthesized. The structures of the complexes [Ln2(3-TAA)6(dmbpy)2] [Ln = Eu(III), Tb(III), Gd(III)] were determined by single crystal X-ray diffraction, where all crystals are isostructural and belong to the triclinic crystal system with P-1 space group. The complexes were characterized by CHN elemental analysis and spectroscopic techniques in the Infra-red region and Raman scattering. The dimeric structures have different modes of coordination using carboxylic and nitrogen groups present in the ligands. To investigate the photoluminescence properties, the Eu(III) and Gd(III) complexes was selected. The triplet state (23,529 cm−1) was determined by the emission spectrum of the Gd(III) complex. Sparkle/PM3 model was also used to predict the ground state geometries of the Eu(III) complex. The intensity parameters (Ω2, Ω4 and Ω6), energy transfer rates, radiative and non-radiative rates (Arad and Anrad), quantum efficiency (η) and quantum yield (q) were determined by quantum mechanics calculation using the LUMPAC software. Crystal structures, spectroscopic properties and their photoluminescence behavior are discussed.

Influence of ZnF2 and ZnCl2 on luminescence investigations and crystal field calculation of Eu3+ doped zinc oxide-phosphate glasses

A series of Eu3+-doped 70NaPO3–20ZnO-10(ZnF2/ZnCl2) glasses were prepared by conventional melting quenching method. The samples were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), electron probe microanalysis (EDS/WDS) and optical spectroscopy. Using the emission spectra a set of Judd-Ofelt (JO) intensity parameters (Ω2, Ω4, Ω6) was refined, which in turn permitted to calculate transition probabilities (AED, AMD), branching ratios (β), radiative lifetimes (τrad) and stimulated emission cross-sections for the 5D0-7FJ transitions. The relative luminescence intensity ratio of 5D0-7F2-5D0-7F1 transitions has been evaluated to estimate the local site symmetry around the Eu3+ ions. Second and fourth rank crystal-field (CF) parameters together with the CF strength parameter have been reported for the first time for such study by assuming the C2v symmetry for the Eu3+ ions in both the phosphate glasses. Large stimulated emission cross-section, high branching ratios and quantum efficiencies (∼80%), also, intense red luminescence at 616 nm confirm that these present glasses suggesting for visible red lasers materials and optical devices.

Bulk growth and polarized spectral characters of Nd:LaCa4O(BO3)3 crystals

A bulk Nd:LaCa4O(BO3)3 (Nd:LaCOB) single crystal with the low Nd3+-doping concentration (~0.5 at%) was grown by Czochralski (Cz) method. Its powder X-ray diffraction, Nd3+ ions doping concentration, polarized transmittance and emission spectra, and fluorescence lifetimes were tested. Based on the Judd-Ofelt theory, the spectral parameters of Nd:LaCOB (Nd3+, ~0.5 at%) crystals including polarized absorption and emission cross sections, spontaneous transition probability, fluorescence branching ratio, theoretical fluorescence lifetime and intensity parameters (Ω2, Ω4 and Ω6) were systemically investigated. The calculated radiation lifetimes were compared with the experimental values, resulting in a quantum yield of 33%, which was the highest record among all the Nd:ReCOB (Re: Y, Gd, La1−xGdx) type crystals. The spectral properties of Nd:LaCOB were found to be better than those of Nd:YCOB and Nd:GdCOB crystals, especially in polarized absorption and emission cross sections. The self-frequency-doubling (SFD) angles were calculated according to the main fluorescence peaks of Nd:LaCOB (Nd3+, ~0.5 at%) crystals such as 1041 nm, 1060 nm, 1090 nm and 1102 nm, which would be excited and frequency doubled into blue-green, green, yellow-green and yellow lasers. All the results showed that the Nd:LaCOB crystals had potential applications in the field of laser and SFD.