Standard Judd Ofelt Research Articles

Synthesis and luminescence investigation of Tb3+–Yb3+ codoped CdF2 single crystals

Tb3+ (1%), Yb3+ (5%):CdF2 single crystals with good optical quality are grown by the standard Bridgman method. The crystal structure is checked by means of X-ray diffraction analysis. Absorption, excitation and fluorescence spectra are carried out at room temperature. The standard Judd–Ofelt (JO) model is applied to absorption intensities of Tb3+ to obtain the three phenomenological intensity parameters by the least square fit procedure. The values obtained are Ω2=2.40, Ω4=2.03 and Ω6=3.60 in 10–20cm2 units, with root mean square of δ=0.1×10–20cm2. These JO intensity parameters are then applied to determine the radiative transition probabilities (AJJ'), radiative lifetimes (τrad) and branching ratios (βJJ') of Tb3+ transitions. We focused on the blue and green transitions from 5D3 and 5D4 levels which occur with relatively high transition probabilities and branching ratios.The fluorescence spectrum exhibits two groups of lines well resolved from 5D3 and 5D4 manifolds (5D3, 5D4→7FJ, J=6, 5, 4, 3, 2). This spectrum is characterized by two strong lines corresponding to 5D3→7F5 (violet/blue line) and 5D4→7F5 (green line) transitions. For the main transitions, there is a good agreement between the fluorescence spectrum and the spontaneous emission probabilities given by the JO analysis.We also performed fluorescence decay spectra and measured the lifetime of 5D3 and 5D4 levels. This have led us to obtain the quantum efficiency of the two transitions 5D3, 5D4→7F5. For the green transition, the value of radiative quantum efficiency obtained is high, which reflects that multiphonon relaxation is limited. The reduced quantum efficiency of the transition from 5D3 manifold shows the happening of a cross relaxation process between Tb3+ ions as follows: 5D3+7F6→5D4+7F0, because of the closely matched energy difference between (5D3, 5D4), and (7F6, 7F0) levels. These parameters suggest that the studied host has the potential to produce intense green emission.

Enhanced 2 μm broad-band emission and NIR to visible frequency up-conversion from Ho3+/Yb3+ co-doped Bi2O3–GeO2–ZnO glasses

In this work, a new and non-conventional oxide glass composition based on Bi2O3–GeO2–ZnO system has been formulated with an aim to realize low phonon oxide glass and elucidate its performance when co-doped with Ho3+/Yb3+ for the energy transfer based NIR emission at 2μm from Ho3+ ions under Yb3+ excitation. The glass with 1.0mol% Ho2O3 and 0.5mol% Yb2O3 has exhibited maximum energy transfer rate (3602s−1) and energy transfer efficiency (65.92%). Important radiative properties have been predicted for emission transitions of Ho3+ ions using intensity parameters derived from measured absorption spectra using standard Judd–Ofelt theory. At lower acceptor ion concentration (0.1mol%), an efficient NIR to visible up-conversion emission has been observed based on two photon absorption process which has found to be reduced significantly at higher Ho3+ concentrations with simultaneous enhancement in 2μm emission. Hence, this newly developed glass codoped with Yb3+/Ho3+ is promising glass for sensitized 2μm emission applications as broad band tunable lasers because of the combination of low phonon energy (707cm−1), high energy transfer efficiency, moderately high emission cross-section (5.33×10−21cm2) and larger effective half-width of the emission band value of 169nm.

Spectroscopic investigations on Tb3+ doped lead fluoroborate glasses

This article presents the optical properties of Tb3+ in lead fluoroborate glasses of the type X PbF2·(89–X)B2O3·10 Al2O3·1Tb2O3 (where X=8, 12, 16, 20, 24, 28, 34 and 36). The standard Judd–Ofelt model was applied to the room temperature absorption intensities of Tb3+ (4f8) to determine the phenomenological intensity parameters Ω2, Ω4 and Ω6. These parameters have been used to calculate radiative transition probabilities (Arad), lifetimes (τR) and branching ratios (βR) for the excited level 5D4. The predicted values of τR are compared with the measured values for 5D4 level for eight glass compositions (Glass (A–H)). Among the eight-terbium glasses Glass A with 8mol% of PbF2 (as the optimum content) has revealed an intense green emission with maximum life time and higher quantum efficiency. The stimulated emission cross section σ(λP) is also evaluated for the 5D4→7FJ (J=6, 5, 4 and 3) transitions.

Crystal growth and spectroscopic studies of novel Yb-doped K5Nd(MoO4)4 single crystals

K5Nd(MoO4)4 crystals with different Yb3+ concentrations were grown using Czochralski technique. Room-temperature absorption spectra were recorded and assigned on the basis of Dieke's diagram for Nd3+ ion; the standard Judd–Ofelt theory has been used to analyze the spectra. Increase of Yb3+ concentration leads to variation of the corresponding Judd–Ofelt intensity parameters. Significant contribution of the Yb↔Nd energy transfer into the formation of the Nd3+ absorption spectra causes the observed changes. After illumination of the crystals with CW Nd:YAG laser changes of the birefringence for the laser line of CW He–Ne laser at 633nm were studied. Birefringence changes show good correlation with the content of Yb ions.

Spectroscopic studies of emission and absorption properties of 38PbO-62SiO 2:Nd 3+ glass

The main spectroscopic parameters (intensity parameters, radiative life times, branching ratios, quantum efficiency and emission cross-section of the 4F 3/2→ 4I 9/2 transition) of the 38PbO-62SiO 2 glass doped with Nd 3+ are evaluated using the standard Judd–Ofelt theory. Remarkably low values of the intensity parameters Ω 2,4,6 are explained by structural modifications of the Nd 3+ surroundings caused by presence of the Pb ions.

Calculating line intensities of 1S0 emission through standard and modified Judd–Ofelt theories inPr3+-dopedCaAl12O19 andSrAl12O19

A modified Judd–Ofelt theory is used in this paper to treat the electric dipole transitions within the4f2 configurationof Pr3+ by considering two main perturbing components of 4f5d and4fn′g. Through the energy-level calculation and standard tensorialanalysis, the explicit distance between the 4f5d configuration and the 1S0 state andother lower 4f2 energy levels are determined. The rare-earth ionPr3+ substitutedat Sr2+ sites inSrAl12O19 (SAO) andCa2+ sites inCaAl12O19 (CAO) has the sitesymmetry of D3h. The standardJudd–Ofelt parameters A332, A334,A534,A536,A736 are included in the calculation, together with odd-λ parametersA333 andA535. The emitting line intensities originating from 1S0 and3P0 are then calculated. Compared with the experimental measurements, the modified modelyields better results than the standard Judd–Ofelt theory.

Judd–Ofelt analysis and optically stimulated two-photon absorption of Yb3+-doped NdAl3(BO3)4 single crystals

Abstract NdAl 3 (BO 3 ) 4 single crystals with different concentrations of Yb 3+ were grown using the top seeded solution growth method. The absorption spectra of the grown samples were recorded at room temperature and analyzed using the standard Judd–Ofelt theory. Influence of Yb 3+ concentration on the Nd 3+ absorption properties was studied. Variation of the Nd 3+ oscillator strengths with changing Yb 3+ concentration suggests significant role of the Yb–Nd energy transfer in the formation of the absorption spectra. Following the absorption spectra we illuminated the investigated crystals at 532 nm absorption line to observe the changes of the two-photon absorption (TPA). We observed substantial increase of the TPA with the increased power of the illuminating laser which was proportional to the Yb content.

Crystal growth and Judd–Ofelt analysis of novel Yb-doped RbNd(WO 4) 2 single crystals

RbNd(WO 4) 2 single crystals with different concentrations of Yb 3+ have been grown using the top seeded solution growth. Room-temperature absorption spectra were assigned on the basis of the Dieke's diagram for Nd 3+ ion and analyzed by means of the standard Judd–Ofelt theory. It was shown that the increase of the Yb 3+ concentration and corresponding decrease of the Nd 3+ concentration leads to the increase of the corresponding Judd–Ofelt intensity parameters, which suggests significant contribution of the Yb–Nd energy transfer in the formation of the absorption spectra.

Optical spectra and luminescence dynamics of the Dy-doped Gd2SiO5 single crystal

Spectroscopic properties of the Dy3+:Gd2SiO5 (GSO) single crystal were investigated. The polarized absorption and unpolarized emission spectra were measured at temperature ranging from 10 K to 300 K. Experimental oscillator strengths were determined from room temperature polarized absorption spectra and phenomenological intensity parameters Ω t were calculated by using the standard Judd–Ofelt theory. Low-temperature measurements were used to determine the energy level structure of two nonequivalent Dy3+ sites in the GSO crystalline host. Analysis of spectra and decay curves of the 4F9/2 emission revealed that Dy3+ ions entering nine-coordinated sites with C 3v symmetry and Dy3+ ions entering the seven-coordinated sites with C s symmetry form two distinct, well-isolated subsystems weakly coupled by the spectral energy migration process. In addition to dissimilar crystal field splitting of multiplets, the two subsystems differ significantly in the efficiency of excitation energy transfer between dysprosium ions, thereby showing dissimilar self-quenching of the 4F9/2 emission. Besides, only one of the two Dy3+ subsystems is coupled to Gd3+ ions by nonradiative Gd3+–Dy3+ energy transfer process. Laser potential related to the 4F9/2→6H13/2 yellow luminescence of dysprosium ions was assessed based on evaluation of the emission cross-section values. It was concluded that the Dy:Gd2SiO5 (Dy:GSO) is a promising material for the visible laser operation.

Spectroscopy of infrared transitions of Pr 3+ ions in Ga–Ge–Sb–Se glasses

Electronic transitions of Pr 3+ ions in Ga–Ge–Sb–Se glasses corresponding to emissions in the infrared region were studied by means of absorption and emission spectroscopies and fluorescence lifetimes measurements. Transition probabilities, radiative lifetimes, branching ratios, and quantum efficiencies of most of the emission transitions including the infrared ones occurring around 1.3, 1.7, and 2.4 μm were estimated based on a standard Judd–Ofelt analysis.

Preparation and spectroscopic characterization of Nd3+:Y2O3 nanocrystals suspended in polymethyl methacrylate

We describe a method to fabricate polymethyl methacrylate (PMMA), a polymeric host, in which nanocrystals of Nd3+:Y2O3 are suspended. The spectroscopic properties of this material are analyzed using the standard Judd–Ofelt technique. The phenomenological Judd–Ofelt intensity parameters are used to calculate the radiative decay rates and the branching ratios of the F43/2→I4J (J=9/2, 11/2, 13/2, and 15/2) intermanifold transitions. The room temperature fluorescence lifetime has been measured for the most intense F43/2→I411/2 emission transition. Emission cross sections for the intense intermanifold transitions and peak emission cross sections for the intense inter-Stark transitions are also reported. Assignments to individual Stark levels of the I4J manifolds have been made and compared with the calculated splittings reported earlier. Finally, the spectroscopic properties of the Nd3+:Y2O3 nanocrystals suspended in PMMA are compared with those of Nd3+ doped in various host materials. Detailed optical analysis led to favorable values of fluorescence lifetime and emission cross section for the F43/2→I411/2 transition, which suggest that the Nd3+:Y2O3 nanocrystals embedded in PMMA would have potential for various photonic applications including laser systems and optical communication devices.

Formula omitted] electric dipole transitions; old problems in a new light

Very well known difficulties of the theoretical description of the f ↔ f electric dipole transitions of lanthanides are addressed in the old language of the standard Judd–Ofelt (J–O) theory, which has been widely applied for more than 45 years. New light is shed on a competitive physical mechanism of these transitions, which is presented to complement the existing J–O model. Possible new solutions are given for the old problems of the negative intensity parameters obtained from the adjusting procedure. An alternative scheme for the reproduction of the hypersensitive transitions is discussed and a theoretical description of highly forbidden transitions 0–0 and 0–1 observed for Eu 3+ and Sm 2+ ions is presented.

Spectroscopic properties of Er 3+-doped xGeO 2–(80 − x)TeO 2–10ZnO–10BaO glasses

Erbium-doped glasses with composition xGeO 2–(80 − x)TeO 2–10ZnO–10BaO were prepared by melt-quenching technique. The phonon sideband spectra and the optical absorption band edges for the host matrix were confirmed by means of the spectral measurements. Standard Judd–Ofelt calculations have been completed to these glasses. The dependence of up-conversion and infrared emission under 980 nm excitation on the glass composition was studied. The quantum efficiencies for the 4I 13/2 → 4I 15/2 transition of trivalent erbium in the glasses were estimated.

Effect of the odd intensity parameters and optical properties of Tb3+ doped fluoroindate glasses

In the present paper we report on the detailed spectroscopic analysis of the Tb 3+ -doped fluoroindate glasses with different Tb 3+ concentration. Absorption spectra in the spectral range from 320 to 6,000 nm were recorded and analyzed for all samples by applying the standard and modified Judd-Ofelt theory. It is well known that in some cases application of the standard Judd-Ofelt theory results in getting negative values for the Ω 2 intensity parameter, which is in obvious contradiction to the definition of the Ω λ (λ = 2, 4, 6) parameters. We demonstrate that it is possible to obtain positive values for all intensity parameters Ω λ by including the odd intensity parameters (λ = 1, 3, 5). Using the standard and modified Judd-Ofelt theory, we obtained the values of the intensity parameters and calculated the oscillator strengths and branching ratios for electric dipole optical transitions in all samples. Comparison with experimental data is discussed.

Optical characterization and ligand-field splitting of Er3+(4f11) energy levels in a fluorine containing tellurite glass

An in-depth spectroscopic study is performed on Er3+(4f11) ions doped into a fluorine containing (lead, lanthanum)-tellurite glass host, containing nominal 1.93at.% of Er3+. The standard Judd-Ofelt (JO) model is applied to the room temperature absorption intensities of Er3+(4f11) transitions in the tellurite glass host to obtain three phenomenological intensity parameters, Ω2, Ω4, and Ω6. These parameters are subsequently used to determine the radiative decay rates, radiative lifetimes, and branching ratios of the Er3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds LJ2S+1 of Er3+(4f11) in the tellurite glass host. The emission cross sections of the intermanifold Er3+ I13∕24→I15∕24 (1.5μm) and S3∕24→I15∕24 (540nm) transitions have been determined. The room temperature fluorescence lifetimes of the I13∕24→I15∕24 and S3∕24→I15∕24 transitions in this tellurite glass host were also measured. From the radiative lifetime determined from the JO model and measured fluorescence lifetime, the quantum efficiency of this material was also determined. The spectroscopic properties were compared with those of Er3+(4f11) in other halotellurite glass hosts. We also analyzed the band structure observed in the absorption spectra of Er3+ in the tellurite glass at 8K. The structure can be interpreted in terms of the ligand-field splitting of the energy levels of the Er3+ ion in the local environment established by the glass matrix into which Er2O3 has been introduced. The spectroscopic analysis of Er3+(4f11) suggests that the tellurite glass is an excellent candidate for various photonic applications.

Spectroscopic properties of Er3+ in Sc:LiNbO3 crystal

The results of Er3+ ion spectroscopic analysis in Sc:LiNbO3 crystals were reported. The line strengths from the ground state to the excited state were evaluated from the measured unpolarized absorption spectrum and analyzed by using standard Judd–Ofelt theory. For Sc(3 mol. %):Er (1 mol. %):LiNbO3 crystal, the obtained intensity parameters are: Ω2=3.72×10-20 cm2, Ω4=1.07×10-20 cm2, and Ω6=0.98×10-20 cm2. The fluorescence spectra and microsecond time-resolved spectra were investigated in the visible region. The excited state absorption transition strengths at 800 nm excitation were evaluated based on Judd–Ofelt theory. The results obtained here were compared to results from other research on Er:LiNbO3 crystals.

Optical absorption intensities of trivalent erbium in a 2-hydroxyethyl methacrylate (HEMA) polymeric host

The standard Judd–Ofelt model has been applied to the room temperature absorption intensities of Er3+(4f11) transitions in a plastic host 2-hydroxyethyl methacrylate, referred to as HEMA, to determine the three phenomenological intensity parameters: Ω2, Ω4, and Ω6. Values are used to determine the spectroscopic quality factor for Er3+ in HEMA and are compared to those for Er3+ in crystalline hosts. The intensity parameters are subsequently used to determine the radiative decay rates and branching ratios of the Er3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds 2S+1LJ of Er3+(4f11) in HEMA. Using the radiative decay rates for Er3+(4f11) transitions between the corresponding excited states and the lower-lying states, the radiative lifetimes of eight excited states are determined.

Effect of lithium-potassium mixed alkali on spectroscopic properties of Er3+-doped aluminophosphate glasses

Er3+-doped lithium-potassium mixed alkali aluminophosphate glasses belonging to the oxide system xK2O-(15-x)Li2O-4B2O3-11Al2O3-5BaO-65P2O5 are obtained in a semi-continuous melting quenching process. Spectroscopic properties of Er3+-doped glass matrix have been analysed by fitting the experimental data with the standard Judd–Ofelt theory. It is observed that Judd–Ofelt intensity parameters Ωt (t = 2, 4 and 6) of Er3+ change when the second alkali is introduced into glass matrix. The variation of line strength Sed[4I13/2,4I15/2] follows the same trend as that of the Ω6 parameter. The effect of mixed alkali on the spectroscopic properties of the aluminophosphate glasses, such as absorption cross-section, stimulated emission cross-section, spontaneous emission probability, branching ratio and the radiative lifetime, has also been investigated in this paper.

New parametrization of spectra of Nd3+ and Sm3+ in glasses

The semi-empirical realization of the Judd-Ofelt theory of f ↔ f transitions has proved to be a powerful tool for the reproduction of the majority of the observed lines in lanthanide doped materials. However, the theoretical description of some of the observed transitions is beyond the framework of the standard approach. In order to describe such transitions, which in particular are forbidden and hypersensitive, Smentek and Wybourne extended the standard theory by relativistic terms and introduced a new parametrization scheme of f-spectra. This parametrization scheme, which is still one-particle but based on double tensor operators, is applied here in order to reproduce the spectra observed in Nd 3+ and Sm 3+ in glasses. The results of numerical calculations are compared to experimental values and to those obtained within the standard Judd-Ofelt scheme as well as its version extended by the odd rank intensity parameters.

Hyperfine‐Induced f↔f Transitions: Effective Operator Formulation

The direct perturbing influence of the nuclear magnetic and electric multipole hyperfine interactions upon the amplitude of the f↔f electric dipole transitions is analyzed. In this approach, the role of the forcing mechanism is played by an interaction other than the crystal field potential, which is the origin of all existing theoretical models. In particular, new effective operators of the second order that result from the electric dipole hyperfine interactions and compete with the standard Judd–Ofelt terms are introduced. In addition, the tensorial structure of the third‐order effective operators that contribute to the transition amplitude is discussed, and attention is directed to the possibility and necessity of the introduction of a new parameterization scheme of f‐spectra that would be applicable for the description of the hypersensitivity and such transitions that are highly forbidden by the standard selection rules.