Physical,structural and optical studies on magnesium borate glasses doped with dysprosium ion

Intense visible emissions from dysprosium(Dy3+) ions doped glasses became prospective for diverse technological applications. In this paper, physical, optical and structural properties of magnesium borate glasses doped with varied concentrations of Dy_2 O_3 were examined. Such glasses were synthesised by melt quenching method and characterized at room temperature using several analytical techniques.Luminescence and absorption spectra(in the visible region) of as-quenched samples were used to evaluate the physical and optical properties. XRD pattern confims the amorphous state of as-quenched samples. The Fourier transform infrared(FTIR) spectra of glasses reveal various bonding vibrations assigned to different functional groups. UV-vis-NIR spectra disclose eight absorption bands accompanied by a band for hypersensitive transition positioned at 1260 nm(~6 H_(15/2)→~6 F_(11/2)). The values of direct and indirect optical energy band gap of the studied glasses are decreased with the increase of Dy~(3+) ion contents. The photoluminescence spectra of all glasses under the excitation of 380 nm display two prominent emission bands centred at 497 nm(~4 F_(9/2)→~6 H_(15/2), blue) and 587 nm(~4 F_(9/2) →~6 H_(13/2), green).The achieved intense luminescence from the proposed glass composition may be beneficial for solidstate laser applications.     

Structural and luminescence studies of europium ions in lithium aluminium borophosphate glasses

Eu3+ doped borophosphate glasses with the chemical composition 20Li2O-30Al2O3-10B2O3-40P2O5-xEu2O3(where x=0.05 mol.%, 0.1 mol.%, 1.0 mol.%, 1.5 mol.% and 2.0 mol.%) were prepared by conventional melt quenching technique. The structural and luminescence properties of the prepared Eu3+ doped borophosphate glasses were studied and compared with reported results. The XRD pattern showed the amorphous nature of the prepared glasses. Whereas, the FTIR spectra revealed the vibrational modes in the prepared glasses. The bonding parameters( β and ?) were calculated through the excitation spectra. Judd–Ofelt(J–O) intensity parameters were calculated from the emission spectra and were used to determine transition probability(A), stimulated emission cross-section(σE P), radiative lifetime(τR) and branching ratios(βexp) for the transition 5D0→7Fj(j=1, 2, 3 and 4) of Eu3+ ions. Furthermore, the luminescence intensity ratio(R) of 5D0→7F2 to 5D0→7F1 transition was also calculated. Transition 5D0→7F2 had the highest value of stimulated emission cross-section and branching ratios and the results were comparable with the reported values. This indicated that the present glass is promising host material for Eu3+ doped fiber amplifiers.     

Spectroscopic investigations and luminescence spectra of Sm3+ doped soda lime silicate glasses

Sm3+ doped soda lime silicate glasses co-doped with As2O3 were prepared and characterised by measuring their absorption spectra in UV-VIS/NIR regions and luminescence spectra in the visible region. Judd-Ofelt intensity parameters, Ωλ, were evaluated from the measured intensifies of the various absorption bands. Ωλ parameters of these glasses were compared with the Ωλ parameters of other reported Sm3+ glasses to study the bonding environment surrounding the Sm3+ in the present glasses. Presence of [AsO4]3- tetrahedra in the second coordination sphere around the central Sm3+ ion made these glasses less covalent as compared to other oxide glasses but the ratio Ω4/Ω6 of the～1.83 indicated them to be fairly stable. With the help of Ωλ parameters and luminescence data for various emission lines, radiative properties for different emission lines were calculated. The values of radiative properties indicated that 4G5/2→6H7/2 and 4G5/2→6H9/2 transitions responsible for orange luminescence might be used in the development of materials for LED's and other optical devices in the visible region.     

Effect of Nd~(3+) on spectroscopic properties of lithium borate glasses

The spectroscopic properties of lithium borate glasses as a function of Nd3＋ ions concentration were reported.Optical absorption spectra of these glasses showed a number of absorption bands in ultra violet and visible region.Optical absorption edge was found to shift towards the longer wavelength（red shift） with increase in Nd2O3.Luminescence spectra revealed three major bands at 902, 1063 and 1334 nm which was due to 4F3/2→4I9/2, 11/2 ＆13/2 transitions of Nd3＋ ions.Luminescence intensity was maximum for 1 mol.% Nd2O3 and further increase in Nd2O3 resulted in luminescence quenching.The luminescence quenching behavior at higher concentration of Nd2O3 was attributed to the Nd3＋-Nd3＋ interaction in the glass matrix.An absorption and emission property of these glasses suggested that these glasses could be useful for 1.06 μm infrared laser applications.     

Energy transfer and frequency upconversion in Er~（3＋）-Yb~（3＋） codoped oxy-fluoro-tungstosilicate glasses

Er3+-Yb3+ codoped oxy-fluoro-tungstosilicate glasses with infrared-to-visible frequency upconversion luminescence were prepared by melting quenching in air.The effects of Er3+ doping on the optical properties of the samples were measured by means of techniques such as optical absorption spectra and photoluminescence spectra.The results showed that intense green and red signals centered at 546 and 665 nm,corresponding to the 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ by a multiphoton stepwise phonon-assisted excited-state absorption process,respectively,were simultaneously observed by exciting the samples with a diode laser operating at 980 nm at room temperature.The upconversion process was found very sensitive to Er3+ content at a constant Yb2O3 content of 5 mol.%.With the increase of Er3+ content from 0.5% to 1.5%,the upconversion intensity increased gradually.Further increasing of Er3+ content to 3.0% resulted in a significant fluorescence quenching.Moreover,the possible upconversion mechanisms were discussed based on the energy-matching conditions and the quadratic dependence on excitation power.     

Spectroscopic Properties and Effect of Radiation Trapping of a New Er^3＋/Yb^3＋ Co-Doped Tellurite-Silicate Glasses

A new serials of Er^3＋/Yb^3＋ co-doped tellurite-silicate glasses were prepared by the technique of high-temperature mehing. The thermal stability, absorption spectra, emission spectra and upconversion spectra were measured and investigated. It is found that these kinds of glasses have good thermal stability, broad FWHM and large stimulated emission cross-section. The three upconversion emission at 525, 546, 658 nm, corresponding to the ^2H11/2→^4Ⅰ15/2, ^4S3/2→4^Ⅰ15/2 and ^F9/2→^4Ⅰ15/2 transitions of Dr^3＋ ions,     

Composition-dependent optical transitions and 2.0 μm emission properties of Ho~(3+) in xGeO_2-(80-x)TeO_2-9.5ZnF_2-10NaF-0.5Ho_2O_3 glasses

Ho3+ doped glasses with various compositions xGeO2-(80-x)TeO2-9.5ZnF2-10NaF-0.5Ho2O3(x=0,10,20,30,40,50,60,70 and80) were prepared by a melt-quenching technique.The composition-dependent optical transition properties of Ho3+ were investigated in theframework of Judd-Ofelt theory.The emission cross sections for 5I7→5I8 transition of Ho3+ in these glasses were calculated according toMcCumber theory,and their compositional dependence was discussed.A simple method was proposed in calculating the emission cross ...     

2 μm mid-infrared optical spectra of Tm3+-doped germanium gallate glasses

Glasses with the composition of 65GeO212Ga2O3-10BaO-8Li2O-5La2O3(molar ratio) doped with 1.526 wt.%, 3.006 wt.%, 5.836 wt.%, 11.028 wt.%, and 15.678 wt.% Tm2O3, respectively, were fabricated by conventional melting method. According to the absorption spectra and the Judd-Ofelt theory, the J-O strength parameters (Ω2,Ω4, Ω6) were calculated, with which the radiative transition probabilities,branching ratios and radiative lifetimes were obtained. The infrared emission spectra (with 808 nm LD excitation) at～1.47 and～1.8 μm of various concentrations of Tm3+-doped glasses were studied. The emission intensity at～1.8 μm reached to the maximum when the Tm2O3-doping concentration was near to be～3.006 wt.% (1.0 mol.%), and then decreased as doping concentration increased further. The mechanism of the fluorescence intensity change was explained with the cross-relaxation effect and the concentration quenching effect of Tm3+. Meanwhile, according to McCumber theory, the absorption and emission cross-sections corresponding to the 3F4→3H6 transitions of Tm3+ at 1.8 μm was obtained. For Tm3+-doped germanate glasses, the maximum emission cross-section reached a value higher than that re-ported for fluorozircoaluminate glasses. It is expected to be a favorable candidate host for～2.0 μm mid-inflated laser because the glass shows favorable optical spectra.     

Optical properties and radiative rates of Nd3+ doped zinc-sodium phosphate glasses

Preparation using melt quenching technique and optical characterizations of Nd~(3+) doped Zn-Na phosphate glasses are presented. The structure of the present glasses was studied using X-ray diffraction and FT-IR spectroscopy. UV-vis spectra of the present glasses were analyzed at different concentrations of Nd_2 O_3. The effect of neodymium concentration on the density and energy band gap was investigated. The density of the present glasses slightly increases with the increasing of Nd_2 O_3. A small variation of energy band gap with the increasing of neodymium content is observed as well, while E_g values decrease with the increase of Nd_2 O_3 content. The E_g values lie between 4.36 and 4.69 eV. Based on the measured optical spectra, Judd-Ofelt theory was used to determine the optical parameters such as line strengths, optical intensity parameters(Ω_t), transition probabilities, and transition lifetimes. Hypersensitive transitions were identified in the absorption spectrum, the greatest line strengths are recorded at the transitions~2 G_(7/2)+ ~4 G_(5/2), ~4 S_(3/2) + ~4 F_(7/2) and ~4 D_(1/2) + ~4 D_(3/2)+ ~4 D_(5/2) + ~2 I_(11/2) with wavelengths of 580, 475 and 355 nm,respectively. Lifetimes of the important ~4 F_(3/2) laser-level were determined; which show decreasing trend with the increasing of Nd_2 O_3 content and are found to be between 0.838 and 1.595 ms. The uncertainty of the present results was estimated. The RMS deviations were determined, which show lower values than those in the literature.     

Kinetics of fluorescence properties of Eu~(3+) ion in strontium-aluminiumbismuth-borate glasses

Eu3＋ doped strontium-aluminium-bismuth-borate glasses with the chemical composition（50–x）B2O3＋20Bi2O3＋7Al F3＋ 8Sr O＋15Sr F2＋x Eu2O3（where x=0.1 mol.%, 0.5 mol.%, 1.0 mol.% and 1.5 mol.%） were prepared by the conventional melt quenching technique.Structural properties of the prepared glasses were analysed through X-ray diffraction（XRD）, scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS） and Raman spectral techniques.Thermal stability of glass was analysed by differential thermal analysis（DTA） curve.Photoluminescence characteristics were studied using excitation, emission spectra and decay curves of Eu3＋ doped strontium-aluminium-bismuth-borate glasses.The Judd-Ofelt（J-O） intensity parameters, Ωλ（λ=2, 4 and 6） were obtained using emission spectra and was used to identify the nature of Eu3＋ ions with their surrounding ligands.Using J-O parameters the transition probabilities（A）, stimulated emission cross-sections σE p, branching ratios（βR） and radiative lifetimes（τmeas and τcal） were evaluated for the 5D0→7F J（J=0, 1, 2, 3 and 4） transition of Eu3＋ ions in the present glasses.The decay profiles were found to be non exponential for all the concentrations and the measured lifetimes（τmeas） were obtained from the decay profiles.The higher values of A, σE p, βR and quantum efficiency（η） for 5D0→7F2 emission transition at 617 nm confirmed the present glass was as active medium for red laser emission applications.     

Optical and thermoluminescence properties of Lu2Si2O7：Pr single crystal

Single crystal of Lu2Si2O7:Pr was grown by Czochralski method. Transmittance, photoluminescence excitation (PLE) and photo-luminescence (PL) spectra, X-ray excited luminescence (XEL) and fluorescence decay time spectra of the sample were measured and discussed to investigate its optical characteristics. The crystal structure of the as grown Lu2Si2O7:Pr was confirmed to be C2/m. There was a broad absorption peaking at 245 nm in the region from 200-260 nm. The PL spectrum was dominated by fast 3PJ→3HJ band peaking at 524 nm. The XEL spectrum was dominated by the fast 5d14f1→4f2 emission peaking at 265 nm. The 2D (temperature-intensity) and 3D (temperature-wavelength-intensity) thermally stimulated luminescence (TSL) spectra were measured. The Pr3+ ion was found to be the recombination center during the TSL process. Three obvious traps were detected in LPS:Pr single crystal with energy depth at 1.06, 0.78 and 0.67 eV.     

Optical Spectroscopy of Er^3＋ and Er^3＋/Yb^3＋ Co-doped Bi2O3-GeO2-B2O3-ZnO Glasses

The （60 - x）Bi2O3 - xGeO2-30B2O3-10ZnO （x = 5, 10, 20, 30 molar percent） glasses doped with Er^3＋ and Er^3＋/Yb^3＋ were fabricated using the melting method. The thermal stability of the glasses was studied with their DTA curves. The results show that the difference between the glass transition temperature and the crystallization onset temperature increases with the increase of GeO2 content, indicating that the thermal stability of the glass has become better. The absorption spectra were recorded and the stimulated emission cross sections were calculated using the McCumber theory. The Ω2, O4, and Ω6 parameters,the transition probability, the radiative lifetime, and the fluorescence branch ratio of Er^3＋ for optical transition were calculated from their absorption spectra in terms of reduced matrix U^（t）（λ = 2, 4, 6） character for optical transitions. The infrared emission of Er^3＋ was measured upon excitation with 970 nm light and the full width at half-maximum （FWHM） was estimated from the emission spectra. The pumping efficiency and the intensity of the emission at the 1.54 μm band of Er^3＋ were enhanced considerably by co-doping Yb^3＋ .     

Enhanced 1-5 μm near-and mid-infrared emission in Ho~(3+)/Yb~(3+)codoped TeO_2-ZnF_2 oxyfluorotellurite glasses

Intense 1-5 μm infrared emission from near-to mid-infrared was obtained from Ho~(3)+/Yb~(3+)codoped TeO_2-ZnF_2 oxyfluorotellurite glasses which were prepared by melt-quenching method under the 980 nm LD excitation,and the emission intensity can be enhanced with the increase of ZnF_2 content.Judd-Ofelt analysis was used to evaluate the radiative transition parameters of the excited levels according to the absorption spectra.The stimulated emission cross section of ~5 I6→~5 I_8(1.2 μm),~5 I7→~5 I_8(2.0μm),~5 I_6→~5 I_7(2.85 μm) and ~5 I_5→~5 I_6(4.0 μm) transitions were calculated to reach 0.639 × 10~(-20),0.760 ×10~(-20),0.985×10 20 and 0.484 × 10~(-20) cm~2,respectively.The energy transfer coefficients(C_(DA)) are enhanced with the increase of ZnF2 content and phonon contribution ratios of phonon assisted energy transfer process between Ho~(3+) and Yb~(3+)were figured out.Our results demonstrate that these TeO_2-ZnF_2 glasses,which possess good thermal stability and transparency,low phonon energy(about 600 cm~(-1)),excellent near-and mid-infrared emission in the range of 1-5 μm wavelength,would be promising material for infrared optical fibers and infrared lasers.     

Characterization of optical transitions of Eu~（3＋） in lanthanum oxychloride nanophosphor

This paper presented the studies on the optical properties and calculation of spectral parameters of europium doped lanthanum oxychloride nanophosphor for their possible applications in optoelectronic devices. The compound was doped with 0.1 mol% Eu3+ ions. The X-ray diffraction study of prepared sample suggested the tetragonal structure with particle size in the range of 18-21 nm. The photoluminescence (PL) emission spectra showed the bright emission in orange-red region from 580 to 630 nm. The most intense emission peak at 621 nm was due to transition 5D0→7F2 in energy levels of Eu3+ ions. The spectral parameters were calculated from the absorption and emission spectra using Judd-Ofelt intensity parameters. The calculated values of the oscillator strength corresponding to the three transitions 7F1→5D1, 7F1→5D2 and 7F0→5D2 observed at 535, 472 and 465 nm in absorption spectra were 0.30×10-6, 1.36×10-6 and 0.63×10-6, respectively. The value of transi- tion probability (A), stimulated emission cross-section ( ) and radiative lifetime (τrad) corresponding to 621 nm emission peak (transition 5D0→7F2) were 308 s-1, 1.22×10-21 cm2 and 3.24×10-3 s, respectively.     

Luminescence properties of Tm^3＋/Yb^3＋, Er^3＋/Yb^3＋ and Ho^3＋/Yb^3＋ activated calcium tungstate

CaWO4 phosphor activated by the Tm3+/Yb3+,Er3+/Yb3+ and Ho3+/Yb3+ ions were synthesized by a traditional high-temperature solid-state method.The crystal structures and morphologies of the products were characterized by X-ray powders diffraction method(XRD) ,infrared spectra(FT-IR) and scanning electron microscopy(SEM) .The samples were found to show up-conversion luminescence properties.CaWO4 doped with Tm3+/Yb3+ showed blue luminescence characteristic of Tm(III) ion in the range of 460-485 nm,corresponding to the 1G4→3H6 electronic transition.CaWO4 doped with Er3+/Yb3+ showed strong green luminescence at 510-565 nm(2H11/2,4S3/2→4I15/2) and weak red luminescence at 640-685 nm(4F9/2→4I15/2) of Er(III) ion.CaWO4 doped with Ho3+/Yb3+ phosphor emitted green luminescence at 525-560 nm(5S2,5F4→5I8) and red luminescence at 630-670 nm(5F5→5I8) and at 730-770 nm(5S2,5F4→5I7) ,which is the characteristic of Ho(III) ion.     

A novel synthesis method and up-conversion properties of hexagonal-phase NaYF4:Er nano-crystals

A novel synthesis method for hexagonal(β)-phase NaYF4:Er nano-crystals(NCs)which showed up-conversion(UC)from infrared to visible spectral region was developed.The NaYF4:Er NCs were synthesized in oleic acid(OA)and 1-octadecene(ODE)with Y2(CO3)3· xH2O,Er2(CO3)3· xH2O,Na2CO3 and NH4F as precursors.This proposed method was simple and less toxic compared with generally used method so far.The XRD results showed that the molar ratio of OA/ODE and the temperature were key factors for phase control of NaYF4:Er NCs.The UC emission spectra were obtained with the emission wavelength at about 980 nm(4I11/2→4I15/2),800 nm(4I9/2→4I15/2),660 nm(4F9/2→4I15/2)and 540 nm(4S3/2→4I15/2)from Er3+ ions,by excitation wavelength of 1550 nm.The slope values,n,in the pump-power dependence,showed that the emission at 980 and 800 nm were generated by 2-step UC and at 660 nm and 540 nm were 3-step UC.The optical process for the UC excitation was discussed.     

Luminescence properties of calcium tungstate activated by lanthanide(Ⅲ) ions

Calcium tungstate phosphors activated by the Ln3+ ions(Ln=Pr, Nd, Tb, Yb) were synthesized by a traditional high-temperature solid-state method. The crystal structures and morphologies of the products were characterized by scanning electron microscopy(SEM), X-ray powders diffraction(XRD) and infrared spectra(FT-IR). The samples were found to show luminescence properties(down-conversion, DC, at excitation wavelength 254 nm and up-conversion, UC, at excitation wavelength 980 nm). CaWO4 doped with Tb3+/Yb3+ showed green DC and UC luminescence characteristic of Tb(III) ion in the range of 470–660 nm, corresponding to the 5D4→7F6,5,4,3,2 electronic transition. CaWO4 doped with Pr3+/Yb3+ showed week blue, green and red(DC and UC) luminescence of Pr(III) ion, in the wavelength region of 450–700 nm. Emission peaks were ascribed to the 3P1→3H4,5,6, 3P0→3H4,5,6, 3P1→3F2 and 3P0→3F2 transitions, respectively. CaWO4 doped with Nd3+/Yb3+ phosphor emitted orange UC luminescence at 450–690 nm(2P3/2→4I15/2, 4G7/2→4I9/2,11/2,13/2) and strong near-infrared UC luminescence at 720–900 nm(4F7/2+4S3/2→4I9/2, 4F5/2+2H3/2→4I9/2, 4F3/2→4I9/2) which is the characteristic of Nd(III) ion.     

Analysis of europium doped luminescent barium thioaluminate

Europium-doped barium thioaluminate sputtering target was synthesized by powder sintering method and thin film was deposited by radio frequency(RF) sputtering.X-ray diffractometer(XRD) pattern indicated that the main compound of the target was BaAl4S7.Oxygen was the main impurity which led to the formation of BaAl2O4.It was shown that both BaAl4S7 and BaAl2S4 were contained in the as-grown thin films and a 471.7 nm emission peak in the PL spectra appeared due to a combination of BaAl4S7:Eu2+ and BaAl2S4:Eu2+.In addition,the product of oxidation in the film was BaSO4 instead of BaAl2O4 and led to an emission peak at 415.2 nm in the PL spectra assigned to the f→f transition of Eu2+ in the BaSO4 host.     

Electrical and optical properties of lithium borate glasses doped with Nd2O3

Glass series with general formula 25Li2O-(75-x)B2O3-xNd2O3 was prepared by conventional melt quench technique. Electrical and optical characterizations of these glasses were carried out. It was observed that conductivity of glasses decreased and activation energy increased with the addition of Nd2O3. The density and refractive index of the glasses increased while optical band gap and radiation length decreased due to structural changes.     

Spectroscopic investigations on Dy3+ ions doped zinc lead alumino borate glasses for photonic device applications

This paper presents the structural, optical absorption, photoluminescence (PL) and decay spectral properties of Dy~(3+)ions doped zinc lead alumino borate (ZPAB) glasses to elucidate their possible usage in photonic devices such as w-LEDs and lasers. A broad hump shown by the XRD spectrum recorded for an un-doped ZPAB glass confirms its non-crystalline nature. The Judd-Ofelt (J-O) intensity parameter evaluated from the measured oscillator strengths of the absorption spectral features were used to estimate various radiative parameters and also to understand the nature of bonding between Dy~(3+)ions and oxygen ligands. Under 350 nm excitation, the as-prepared glasses are exhibiting two emission bands~4F_(9/2)→~6H_(15/2)(blue),and~4F_(9/2)→~6H_(13/2)(yellow) at 483 and 575 nm,respectively. From the PL spectra,the Y/B ratio values, CIE chromaticity color coordinates and color correlated temperature (CCT) were evaluated. The experimental lifetimes measured from the decay profiles are decreasing with increase in Dy~(3+)ions concentration in these glasses which may be attributed to the cross-relaxation and nonradiative multiphonon relaxation process. Decay profiles observed for higher concentration were well fitted to Inokuti-Hirayama (I-H) model to understand the energy transfer process and subsequent decrease in experimental lifetimes. The higher values of radiative parameters, emission cross-sections,quantum efficiency, optical gain and gain band width suggest the suitability of 0.5 mol%of Dy~(3+) ions in these ZPAB glasses for the photonic device application.