Spectroscopic properties of Dy(3+) ions in NaF-B(2)O(3)-Al(2)O(3) glasses

This paper reports the optical properties of Dy(3+) in sodium fluoroborate glasses of the type XNaF.(89-X)B(2)O(3).10 Al(2)O(3).1Dy(2)O(3) (where X=8, 12, 16, 20 and 24). Judd-Ofelt intensity parameters (Omega(2), Omega(4), Omega(6)) are derived from the absorption spectra. The Judd-Ofelt theory has been applied to interpret the local environment of Dy(3+) ions and bond covalency of RE-O bond. These parameters have been used to calculate radiative transition probabilities (A(rad)), lifetimes (tau(R)) and branching ratios (beta(R)) for the excited level (4)F(9/2). The predicted values of tau(R) are compared with the measured values for (4)F(9/2) level for five glass compositions (Glass (A-E)). The stimulated emission cross-section sigma(lambda(P)) are also evaluated for the (4)F(9/2)-->(6)H(J) (J=11/2, 13/2, and 15/2) transitions.     

Spectroscopic investigations of Nd(3+)-doped alkali chloroborophosphate glasses

Optical absorption spectra were studied in wavelength region 400-900 nm for the Nd(3+)-doped alkali (R = Li, Na and K) chloroborophosphate glasses at room temperature. The energy level scheme of the 4f(3) electron configuration was deduced from the observed energy level data using a parametrized Hamiltonian (H(F1)) model which includes 20 free-ion interaction parameters. Reasonable correlation was obtained between the experimental and calculated energy levels. The Judd-Ofelt model for the intensity analysis of induced electric dipole transitions has been applied to the measured oscillator strengths of the absorption bands to determine the three phenomenological intensity parameters Omega(2), Omega(4) and Omega(6) for each glass. Using these parameters, the total radiative transition rates (A(T)), non-radiative relaxation rates (W(NR)), branching ratios (beta(R)), integrated cross-sections for the stimulated emission (Sigma), excited state emission intensities (f(ESE)) and excited state absorption intensities (f(ESA)) have been theoretically calculated for certain excited Nd(3+) fluorescent levels. From the results obtained, the conclusion is made about the possibility of using these glasses as laser media.     

Effect of Bi2O3 on spectroscopic and structural properties of Er3+ doped cadmium bismuth borate glasses

Glasses with composition 20CdO·xBi(2)O(3)·(79.5-x)B(2)O(3) (15≤x≤35, x in mol%) containing 0.5 mol% of Er(3+) ions were prepared by melt-quench technique (1150°C in air). The amorphous nature of the glasses was confirmed by X-ray diffraction. The spectroscopic properties of the glasses were investigated using optical absorption spectra and fluorescence spectra. The phenomenological Judd-Ofelt intensity parameters Ω(λ) (λ=2, 4, 6) were determined from the spectral intensities of absorption bands in order to calculate the radiative transition probability (A(R)), radiative life time (τ(R)), branching ratios (β(R)) for various excited luminescent states. Using the near infrared emission spectra, full width at half maxima (FWHM), stimulated emission cross-section (σ(e)) and figure of merit (FOM) were evaluated and compared with other hosts. Especially, the numerical values of these parameters indicate that the emission transition (4)I(13/2)→(4)I(15/2) at 1.506 μm in Er(3+)-doped cadmium bismuth borate glasses may be useful in optical communication.     

Optical absorption and photoluminescence properties of Er3+ doped mixed alkali borate glasses

An investigations of the optical absorption and fluorescence spectra of 0.2 mol% Er2O3 in mixed alkali borate glasses of the type 67.8B2O3 x xLi2O(32-x)Na2O, 67.8B2O3 x xLi2O(32-x)K2O and 67.8B2O3 x xNa2O(32-x)K2O (where x = 8, 12, 16, 20 and 24) are presented. The glasses were obtained by quenching melts consisting of H3BO3, Li2CO3, Na2CO3, K2CO3 and Er2O3 (950-1100 degrees C, 1.5-2 h) between two brass plates. Spectroscopic parameters like Racah (E1, E2 and E3), spin-orbit (xi(4f)) and configuration interaction (alpha) parameters are deduced as function of x. Using Judd-Ofelt theory, Judd-Ofelt intensity parameters (omega2, omega4 and omega6) are obtained. Radiative and non-radiative transition rates (A(T) and W(MPR)), radiative lifetimes (tauR), branching ratios (beta) and integrated absorption cross-sections (sigma) have been computed for certain excited states of Er3+ in these mixed alkali borate glasses. Emission spectra have been studied for all the three Er3+ doped mixed alkali borate glasses. The present paper throws light on the trends observed in the intensity parameters, radiative lifetimes, branching ratios and emission cross-sections as a function of x in these borate glasses, keeping in view the effect of mixed alkalies in borate glasses.     

Spectroscopic investigations of Nd3+ doped flouro- and chloro-borate glasses

Spectroscopic and physical properties of Nd(3+) doped sodium lead flouro- and chloro-borate glasses of the type 20NaX-30PbO-49.5B(2)O(3)-0.5Nd(2)O(3) (X=F and Cl) have been investigated. Optical absorption spectra have been used to determine the Slater Condon (F(2), F(4), and F(6)), spin orbit xi(4f) and Racah parameters (E(1), E(2), and E(3)). The oscillator strengths and the intensity parameters Omega(2), Omega(4) and Omega(6) have been determined by the Judd-Ofelt theory, which in turn provide the radiative transition probability (A), total transition probability (A(T)), radiative lifetime (tau(R)) and branching ratio (beta) for the fluorescent level (4)F(3/2). The lasing efficiency of the prepared glasses has been characterized by the spectroscopic quality factor (Omega(4)/Omega(6)), the value of which is in the range of 0.2-1.5, typical for Nd(3+) in different laser hosts. Nephelauxetic effect results in a red shift in the energy levels of Nd(3+) for chloroborate glass. The radiative transition probability of the potential lasing transition (4)F(3/2)-->(4)I(11/2) of Nd(3+) ions is found to be higher for flouroborate as compared to chloroborate glass.     

Absorption and emission characteristics of Er3+ ions in alkali chloroborophosphate glasses

Alkali chloroborophosphate glasses containing 1 mol% of Er3+ ions were studied experimentally using the absorption and emission spectroscopy. The energy level scheme for the 4f11 (Er3+) electronic configuration was deduced from the observed band energies of the absorption spectra in terms of a parametrized Hamiltonian using the various free-ion spectroscopic parameters. Oscillator strengths (f) measured from the absorption spectra have been analyzed using the Judd-Ofelt theory to evaluate the three intensity parameters omegalambda (lambda = 2, 4 and 6). Reasonable agreement between the measured and calculated f values has been found. Electric and magnetic dipole transition probabilities, fluorescence branching ratios, integrated emission cross sections and radiative lifetimes were calculated for all the excited states of Er3+ ions. The non-radiative (WNR) relaxation rates from the excited levels to the next lower levels have been calculated and the relationship between the energy gap and non-radiative relaxation rate has been established. These results were used to predict the possible potential laser transitions in Er-doped alkali chloroborophosphate glasses.     

Fluorescence properties of Nd3+-doped tellurite glasses

The compositional and concentration dependence of luminescence of the (4)F(3/2)-->(4)I(J) (J=13/2, 11/2 and 9/2) transitions in four Nd(3+)-doped tellurite based glasses has been studied. The free-ion energy levels obtained for 60TeO(2)+39ZnO(2)+1.0Nd(2)O(3) (TZN10) glass have been analysed using the free-ion Hamiltonian model and compared with similar results obtained for Nd(3+):glass systems. The absorption spectrum of TZN10 glass has been analysed using the Judd-Ofelt theory. Relatively longer decay rates have been obtained for Nd(3+)-doped phosphotellurite glasses. The emission characteristics of the (4)F(3/2)-->(4)I(11/2) transition, of the Nd(3+):TZN10 glass, are found to be comparable to those obtained for Nd(3+):phosphate laser glasses. The non-exponential shape of the emission decay curves for the (4)F(3/2)-->(4)I(11/2) transition is attributed to the presence of energy transfer processes between the Nd(3+) ions.     

Optical characterization of Sm3+ and Dy3+:ZnO-PbO-B2O3 glasses

Here, we present the results of the analysis of Sm(3+) or Dy(3+) (0.5 mol%) ions doped heavy metal oxide (HMO)-based zinc lead borate (ZLB) glasses. Optical measurements such as absorption, emission spectra, lifetimes, XRD, DSC profiles have been carried out. The emission spectrum of Sm(3+):ZLB has shown the emission transitions of (4)G(5/2)-->(6)H(5/2) (563 nm), (4)G(5/2)-->(6)H(7/2) (598 nm), (4)G(5/2)-->(6)H(9/2) (646 nm), (4)G(5/2)-->(6)H(11/2) (708 nm) with lambda(exc): 401 nm ((6)H(5/2)-->(4)F(7/2)). In the case of the Dy(3+):ZLB glass, emission transitions of (4)F(9/2)-->(6)H(15/2) (485 nm), (4)F(9/2)-->(6)H(13/2) (575 nm) and (4)F(9/2)-->(6)H(11/2) (664 nm) with lambda(exi): 447 nm ((6)H(15/2)-->(4)I(15/2)) have been identified. Energy level schemes relating to the emission mechanisms involved in Sm(3+) and Dy(3+) glasses have been given.     

Characterization of emission properties of Er3+ ions in TeO2-CdF2-WO3 glasses

TeO(2)-CdF(2)-WO(3) glasses with various compositions and Er(3+) concentrations were prepared by conventional melting method. Their optical properties were studied by measuring the absorption, luminescence spectra and the decay patterns at room temperature. From the optical absorption spectra the Judd-Ofelt parameters (Ω(t)), transition probabilities, branching ratios of various transitions, and radiative lifetimes were calculated. The absorption and emission cross-section spectra of the (4)I(15/2) to (4)I(13/2) transition of erbium were determined. Emission quantum efficiencies and the average critical distance R(0) which provides a measure for the strength of cross relaxation were determined.     

Temperature dependent luminescence characteristics of Sm3+-doped silicate glass

We report here on the optical characterisation of Sm3+ (5 wt%): SiO2 + Al2O3 + Li2O + Na2O + MgO glass from the measurements of optical absorption spectra (at 300 K), total luminescence spectra (10-300 K) and fluorescence lifetimes (10-300 K) of the prominent emission transitions of the Sm3+ ions. Besides its spectral properties, physical and nonlinearity characterising property parameters have also been computed to understand the optical dispersive power of this glass. By the application of Judd-Ofelt parameters (omega(lambda)) of the measured absorption spectrum, the radiative transition probability factors (A) and stimulated emission cross-section (sigma(p)E) of the observed fluorescent levels have been analysed. Both emission intensity and measured lifetimes of the prominent luminescent transition (4G(5/2) --> 6H(7/2)) concerning Sm3+-glass has been showing a descending trend with the rise in temperature with N2-laser (337.1 nm) as the source of excitation.     

Electronic absorption spectra and energy gap studies of Er3+ ions in different chlorophosphate glasses

Spectroscopic properties of Er3+ ions in different chlorophosphate glasses 50P2O5-30Na2HPO4-19.8RCl (R = Li, Na, K, Ca and Pb) are studied. The direct and indirect optical band gaps (Eopt) and the various spectroscopic parameters (E1, E2, E3, and zeta4f and alpha) are reported. The oscillator strengths of the transitions in the absorption spectrum are parameterized in terms of three Judd-Ofelt intensity parameters (omega2, omega4 and omega6). These intensity parameters are used to predict the transition probabilities (A), radiative lifetimes (tauR), branching ratios (beta) and integrated cross sections (sigma) for stimulated emission. Attention has been paid to the trend of the intensity parameters over hypersensitive transitions and optical band gaps. The lifetimes and branching ratios of certain transitions are compared with other glass matrices.     

Luminescence properties and quenching mechanisms of Ln(Tf2N)3 complexes in the ionic liquid bmpyr Tf2N

The emission properties, including luminescence lifetimes, of the lanthanide complexes Ln(Tf(2)N)(3) (Tf(2)N = bis(trifluoromethanesulfonyl)amide); Ln(3+) = Eu(3+), Tm(3+), Dy(3+), Sm(3+), Pr(3+), Nd(3+), Er(3+)) in the ionic liquid bmpyr Tf(2)N (bmpyr = 1-n-butyl-1-methylpyrrolidinium) are presented. The luminescence quantum efficiencies, η, and radiative lifetimes, τ(R), are determined for Eu(3+)((5)D(0)), Tm(3+)((1)D(2)), Dy(3+)((4)F(9/2)), Sm(3+)((4)G(5/2)), and Pr(3+)((3)P(0)) emission. The luminescence lifetimes in these systems are remarkably long compared to values typically reported for Ln(3+) complexes in solution, reflecting weak vibrational quenching. The 1.5 μm emission corresponding to the Er(3+) ((4)I(13/2)→(4)I(15/2)) transition, for example, exhibits a lifetime of 77 μs. The multiphonon relaxation rate constants are determined for 10 different Ln(3+) emitting states, and the trend in multiphonon relaxation is analyzed in terms of the energy gap law. The energy gap law does describe the general trend in multiphonon relaxation, but deviations from the trend are much larger than those normally observed for crystal systems. The parameters determined from the energy gap law analysis are consistent with those reported for crystalline hosts. Because Ln(3+) emission is known to be particularly sensitive to quenching by water in bmpyr Tf(2)N, the binding properties of water to Eu(3+) in solutions of Eu(Tf(2)N)(3) in bmpyr Tf(2)N have been quantified. It is observed that water introduced into these systems binds quantitatively to Ln(3+). It is demonstrated that Eu(Tf(2)N)(3) can be used as a reasonable internal standard, both for monitoring the dryness of the solutions and for estimating the quantum efficiencies and radiative lifetimes for visible-emitting [Ln(Tf(2)N)(x)](3-x) complexes in bmpyr Tf(2)N.     

Effect of ZnX (X=F2 and Cl2) as modifier on luminescence properties of Ho3+/Yb3+ doped tellurite glasses

Optical absorption and photoluminescent properties of Ho(3+)/Yb(3+) co-doped tellurite and zinc halide tellurite glasses are investigated. The effect of zinc halides as modifier on the luminescence properties of above mentioned samples has been explored. Two intense upconversion emission bands centered at 546 ((5)F(4), (5)S(2)→(5)I(8)) and 660 ((5)F(5)→(5)I(8)) nm are observed when samples are excited by 976 nm radiation. Zinc halides act as quencher when 976 nm excitation source is used. The up and downconversion emission spectra are recorded with 532 nm excitation source also. In this case also, zinc halides do not show any improvement. The dependence of upconversion intensities on excitation power and temperature is discussed. The power dependence study shows a quadratic dependence of fluorescence intensity on the excitation power while decrement in emission intensity of different transitions at different rates is observed in temperature dependence study. The possible upconversion mechanisms are also discussed in order to understand the energy transfer between Yb(3+) and Ho(3+) ions.     

Enhanced deep-red luminescence of tris(hexafluoroacetylacetonato)samarium(III) complex with phenanthroline in solution by control of ligand coordination

The effect of solvent molecule on the emission properties of Sm(hfa)3(phen)2 (hfa = hexafluoroacetylacetonato, phen = phenanthoroline) was investigated using acetone, acetonitrile, and pyridine. 5G(5/2) --> 5H(9/2) transition intensities in pyridine were found to be larger than those in corresponding acetone and acetonitrile. The radiative rate constant in pyridine (4.8 x 10(2) s(-1)) was 2 times larger than those in acetonitrile (2.6 x 10(2) s(-1)) and acetone (2.3 x 10(2) s(-1)), although the nonradiative transition via vibrational relaxation (k(nr) = 1.7 x 10(4) s(-1)) in pyridine was the same as those in acetone and acetonitrile (k(nr) = 1.8 x 10(4) s(-1)), resulting in the enhanced emission quantum yield of Sm(III) complex in pyridine (2.7%). The coordination structures of Sm(hfa)3(phen)2 in acetonitrile, acetone, and pyridine were estimated by X-ray single-crystal analyses. These results indicate that enhancement of the emission properties in pyridine is due to faster radiative rate related to formation of asymmetrical nine-coordinated structure, Sm(hfa)3(phen)(py) (py = pyridine).     

Photoluminescence and energy transfer studies of Dy(3+)-doped fluorophosphate glasses

Dy(3+)-doped fluorophosphate glasses with composition (in mol%) (56-x/2)P(2)O(5)+17K(2)O+(15-x/2)BaO+8Al(2)O(3) + 4AlF(3)+ xDy(2)O(3), x=0.01, 0.05, 0.1, 1.0 and 2.0, have been prepared by melt quenching technique. The luminescence spectra and lifetimes of (4)F(9/2) level of Dy(3+) ions in these glasses have been measured using the 457.9 nm line of argon ion laser as an excitation source. The free-ion calculation and Judd-Ofelt analysis have been performed. The room temperature emission spectra corresponding to (4)F(9/2)-->(6)H(J) (J=7/2, 9/2, 11/2, 13/2 and 15/2) transitions of Dy(3+) ions were measured. The fluorescence decay from (4)F(9/2) level have been measured by monitoring the intense (4)F(9/2)-->(6)H(13/2) transition. The lifetime of the decay is obtained by taking the first e-folding times of the decay curves and is found to decrease with increase in Dy(3+) ions concentration due to concentration quenching. The decay curves are found to be perfectly single exponential for samples with low Dy(3+) ion concentration. The non-exponential decay curves observed for higher concentrations are well fitted to the Inokuti-Hirayama model for S=6, which indicates that the energy transfer between the donor and acceptor is of dipole-dipole nature. The energy transfer parameter and donor to acceptor interaction increases with Dy(3+) ions concentration due to increase of energy transfer from Dy(3+) (donor) to unexcited Dy(3+) (acceptor) ions.     

Spectroscopic properties of Er3+, Yb3 + and Er3 + /Yb3+ doped metaphosphate glasses

The absorption and emission spectroscopies of Er3+ doped and Er3+/Yb3+ codoped Ca(PO3)2, Sr(PO3)2 and Ba(PO3)2 glasses have been studied. From the Judd-Ofelt intensity parameters, the spontaneous emission probabilities of some relevant transitions and the radiative lifetimes of several excited states of Er3+ have been calculated. The decay curves of the Er3+ emission at 1.5 microm have been measured at different temperatures. The data have been fitted using a stretched exponential function and the obtained experimental lifetimes have been compared with the calculated radiative lifetimes. The difference between the experimental and calculated lifetimes is attributed to the presence of traces of OH groups in the host glasses. The absolute OH content in some glasses has been determined from the infrared spectra. The emission spectra at 1.5 microm of the Er3+ ion in the codoped glasses have been measured at different temperatures. The integrated emission intensities decrease significantly on passing from room temperature to 13 K, suggesting a temperature dependence of the rate of the energy transfer process between Yb3+ and Er3+.     

Effect of fluorine ions on 2.7 μm emission in Er3+/Nd(3+)-codoped fluorotellurite glass

The 2.7 μm emission properties of Er(3+)/Nd(3+)-codoped fluorotellurite glasses were investigated in the present work. The thermal stability, refractive index, absorption and transmission spectra, and emission spectra were measured and investigated. The 2.7 μm emission in Er(3+)/Nd(3+)-codoped fluorotellurite glasses was enhanced with the increase of fluorine ions. The Judd-Ofelt analysis based on absorption spectra was performed in order to determine the Judd-Ofelt intensity parameters Ωt (t = 2, 4, 6), spontaneous emission probability, radiative lifetime and branching ratios of Er(3+):(4)I(11/2) → (4)I(13/2) transition. It is found that the Er(3+)/Nd(3+)-codoped fluorotellurite glass possesses a lower spontaneous transition probability A (58.95 s(-1)) but a higher branching ratio β (15.72%) corresponding to the stimulated emission of Er(3+):(4)I(11/2) → (4)I(13/2) transition. Additionally, the transmittance was also tested and reached a maximum when the molar concentration of ZnF(2) is 15%. The presence of fluorine ions greatly decreases the population of OH(-) groups, which affects the 2.7 μm emission effectively by means of decreasing the rate of energy transfer to impurities (e.g., OH(-) groups).     

Photoluminescence and Raman studies of Sm3+ and Nd3+ ions in zirconia matrices: example of energy transfer and host-guest interactions

Photoluminescence and Raman studies on Sm(3+)- and Nd(3+)-doped zirconia are reported. The Raman studies indicate that the monoclinic (m) phase dominates up to a 10 at.% lanthanide level, while stabilization of the cubic phase is attained at approximately 20 and approximately 25 at.% of Sm(3+) and Nd(3+), respectively. Both systems are strongly luminescent under photo-excitation. The emission spectrum at 77 K of the ZrO(2):Sm(3+) system consists of a broad band at 505 nm, that corresponds to the zirconia matrix. At room temperature the band maximum blue-shifts to 490 nm. Sharper bands corresponding to f-f transitions within the Sm(3+)ion are also exhibited in the longer wavelength region of the spectrum. Exclusive excitation of the zirconia matrix provides sensitized emission from the acceptor Sm(3+) ion. The excitation profile is dominated by a broad band at 325 nm when monitored either at the zirconia or at one of the Sm(3+) emissions. A spectral overlap between the 6H(5/2)-->(4)G(7/2) absorption of the Sm(3+) ion with the zirconia emission leads to an efficient energy transfer process in the systems. Multiple facets of the spectral behavior of the Sm(3+) or Nd(3+) in the zirconia matrices, as well as the effects of compositions on the emission and Raman properties of the materials, and the role of defect centers in photoluminescence and the energy transfer processes are discussed.     

The resonance Raman effect of uranyl chloride in dimethyl sulfoxide

A study was carried out of the resonance Raman scattering spectra of uranyl chloride (UO2Cl2) in dimethyl sulfoxide ((CH3)2SO) (DMSO) under laser excitation of the UO2(2+) ion in resonance with the 1sigma(g)+ --> 1phi(g) Laport-forbidden f-f electronic transitions span from 530 to 450 nm by using ten output lines of the argon-ion laser at room temperature. The resonance Raman excitation profile of the totally symmetric stretching vibrational mode of uranyl observed at 832 cm(-1) is presented and analyzed in terms of transform theory within the non-Condon model to give relatively good agreement with experimental results. The disagreement between the experimental data and the calculated resonance Raman excitation profile, at the long-wave part of the the 1sigma(g)+ --> 1phi(g) electronic transitions, may be referred to interference between the weak scattering from the neighboring forbidden electronic states (1delta(g)) and strong preresonance scattering from allowed electronic states at higher levels. An amount of change in the experimental resonance Raman excitation profile of the uranyl-DMSO system depends considerably upon the ligands (L) bound to the uranyl group. Elongation of the U-O equilibrium bond length resulting from the 1sigma(g)+ --> 1phi(g) electronic transitions is related to the magnitude of the change in the excitation profile of UO2L2 (L = NO3, CH3COO, Cl) type uranyl compounds in (DMSO).     

Effect of bismuth oxide on the thermal stability and Judd-Ofelt parameters of Er3+/Yb3+ co-doped aluminophosphate glasses

The Er3+/Yb3+ co-doped glasses with compositions of xBi2O3-(65-x)P2O5-4Yb2O3-11Al2O3-5BaO-15Na2O (where x=0, 2.5, 5, 7.5 and 10 mol%) were prepared using the normal melt quench technique. The optical absorption spectra of the glasses were recorded in the wavelength range 300-1700 nm. The effect of Bi2O3 content on the thermal stability and absorption spectra of glasses was investigated. In addition, the Judd-Ofelt parameters and oscillator strengths were calculated by employing Judd-Ofelt theory. It was observed that the positions of the fundamental absorption edge and cut-off wavelength shifted towards red as the content of Bi2O3 increased. However, there were no red shifts found both in the peak wavelength and in the center of mass wavelength of all absorption bands with Bi2O3 content increasing. The results of Judd-Ofelt theory analysis showed that Judd-Ofelt parameters Omega t (t=2, 4, 6) changed sharply when Bi2O3 concentration exceeded 5 mol%. The variation trends of experimental oscillator strength were similar with those of Judd-Ofelt parameters as function of Bi2O3 concentrations. Moreover, differential scanning calorimetry experiments showed that the increases of Bi2O3 content weakened the network structure and then lowered the thermal stability of the glasses. The spontaneous emission probability A rad, branching ratio beta and the radiative lifetime tau rad were also calculated and analyzed. The stimulated emission cross-section of Er3+ was calculated according to the McCumber theory. It was found that the stimulated emission cross-section of Er3+ was monotonically increases with Bi2O3 content increasing.