Structural and optical studies of Er3+-doped alkali/alkaline oxide containing zinc boro-aluminosilicate glasses for 1.5 um optical amplifier applications

In the present work, we report on the optical spectral properties of Er3+ -doped zinc boro-aluminosilicate glasses with an addition of 10 mol % alkali/alkaline modifier regarding the fabrication of new optical materials for optical amplifiers. A total of 10 glasses were prepared using melt−quenching technique with the compositions (40-x)B2O3 − 10- SiO2 − 10Al2O3 − 30ZnO − 10Li2O − xEr2O3 and (40-x)B2O3 − 10SiO2 − 10Al2O3 − 30ZnO – 10MgO − xEr2O3 (x = 0.1, 0.25, 0.5, 1.0, and 2.0 mol %). We confirm the amorphous-like structure for all the prepared glasses using X-ray diffraction (XRD). To study the functional groups of the glass composition after the melt−quenching process, Raman spectroscopy was used, and various structural units such as triangular and tetrahedral-borates (BO3 and BO4 ) have been identified. All the samples were characterized using optical absorption for UV, visible and NIR regions. Judd-Ofelt (JO) intensity parameters (Ωλ , λ = 2, 4 and 6) were calculated from the optical absorption spectra of two glasses LiEr 2.0 and MgEr 2.0 (doped with 2 mol % of Er3+). JO parameters for LiEr 2.0 and MgEr 2.0 glasses follow the trend as Ω6>Ω2>Ω4 . Using Judd–Ofelt intensity parameters, we obtained radiative probability A (S−1 ), branching ratios (β), radiative decay lifetimes τrad (μs) of emissions from excited Er+3 ions in LiEr 2.0 and MgEr 2.0 to all lower levels. Quantum efficiency (η) of 4 I13/2 and 4 S3/2 levels for LiEr 2.0 and MgEr 2.0 with and without 4D7/2 level was calculated using the radiative decay lifetimes τrad. (μs) and measured lifetimes τexp. (μs). We measured the visible photoluminescence under 377 nm excitation for both LiEr and MgEr glass series within the region 390–580 nm. Three bands were observed in the visible region at 407 nm, 530 nm, and 554 nm, as a result of 2H9/2 → 4 I15/2 , 2H11/2 → 4 I15/2 and 4 S3/2 → 4 I15/2 transitions, respectively. Decay lifetimes for emissions at 407 nm, 530 nm, and 554 nm were measured and they show single exponential behavior for all the LiEr and MgEr glass series. From the photoluminescence and radiative decay lifetimes (τrad), we calculated the full-width at half-maximum (FWHM), emission cross-section ( ) and bandwidth gain (FWHM ) parameters. Near-infrared photoluminescence under 980 nm excitation was measured for all the LiEr and MgEr glass series in the region 1420–1620 nm. NIR emissions show a broadband centered at ∼1530 nm due to the transition of Er3+: 4 I13/ 2 → 4 I15/2 . Decay lifetimes for NIR emission at ∼1530 nm were measured and they show a quite exponential nature for all the LiEr and MgEr glass series. From the NIR emission spectra and decay lifetimes, we calculated the full-width at half-maximum (FWHM), the emission cross-section ( ) and the bandwidth gain (FWHM ) for the NIR emission and it shows FWHM of 50–70 nm for prepared glasses, emission cross-section of (∼3.5) 10−20 cm2 , while bandwidth gain was (∼25) 10−26 cm3

Optical spectroscopy of zinc metaphosphate glasses activated by Ce3+ and Tb3+ ions

The photoluminescence of Ce3+ and Tb3+ ions in zinc metaphosphate glasses is investigated. The blue and green emissions of Tb3+ ions are enhanced upon UV excitation through energy transfer from Ce3+ to Tb3+ ions. The efficiency of such an energy transfer was estimated based on spectroscopic data and resulted in being about 20-23%. Spectroscopic data revealed that the energy transfer occurs via a non-radiative process inside Ce3+-Tb3+ clusters formed in the glass. This ion clustering could be useful for the design of efficient conversion phosphors of ultraviolet to blue and green light

Spectroscopic evaluation of Zn(PO3)(2):Dy3+ glass as an active medium for solid state yellow laser

A spectroscopic investigation of zinc phosphate glass activated with 1.0, 5.0 and 10.0 mol% of Dy(PO3)(3) is performed through absorption and luminescence spectra and decay times to study its potentialities for yellow laser operation upon excitation at 399 nm, which fits to the requirements of GaN LEDs. In the 1.0 mol% Dy(PO3)(3)-doped glass a quantum efficiency of 80 +/- 5% was estimated for the dysprosium F-4(9/2) level luminescence, the F-4(9/2) -> H-6(13/2) yellow emission shows greater intensity than the F-4(9/2) -> H-6(15/2) blue emission, as well as a very high optical gain, which might make this glass phosphor a promising gain medium for solid state yellow laser pumped by GaN LEDs. (C) 2014 Elsevier B.V. All rights reserved

Energy transfer in Sr0.6Ba0.4Nb2O6 through its ferroelectric phase transition

Resonant Nd3+ -> Yb3+ energy-transfer in the Nd3+ and Yb3+ co-doped Sr0.6Ba0.4(NbO3)(2) (SBN) crystal is investigated by using pulsed and steady state laser spectroscopy. Spectroscopic data revealed that the energy transfer occurs via a non-radiative process. The efficiency of this energy transfer was estimated from spectral data in around 35%. Back energy transfer is not observed at the 295-415 K temperature range. A marked reduction in the luminescence intensity of Yb3+ ions directly excited into their F-2(7/2) -> F-2(5/2) transition, taking place at around 345 K, is due to the ferro to paraelectric phase transition in SBN. This thermal behavior, which is not clearly manifested when Yb3+ ions are excited via Nd3+ ions, has been explained in terms of structural changes taking place around the Yb3+ ions when the crystal becomes non-polar

Blue-yellow photoluminescence from Ce3+ -> Dy3+ energy transfer in HfO2:Ce3+:Dy3+ films deposited by ultrasonic spray pyrolysis

HfO2 films codoped with Ce3+ and several concentrations of Dy3+ have been processed by the ultrasonic spray pyrolysis technique. Emissions from Dy3+ ions centred at 480 and 575 nm associated with the 4F9/2 \u2192 6H15/2 and 4F9/2 \u2192 6H13/2 transitions, respectively, have been observed upon UV excitation via a non-radiative energy transfer from Ce3+ to Dy3+ ions. Such energy transfer via an electric dipole\u2013quadrupole interaction appears to be the most probable transfer mechanism. The efficiency of this transfer increases up to 86 \ub1 3% for the film with the highest Dy3+ content (1.9 \ub1 0.1 at.% as measured from EDS). The possibility of achieving the coordinates of ideal white light with increasing the concentration of dysprosium is demonstrated

Blue-green-red luminescence from CeCl3-and MnCl2-doped hafnium oxide layers prepared by ultrasonic spray pyrolysis

Hafnium oxide films doped with CeCl(3) and/or MnCl(2), and deposited at 300 degrees C by an ultrasonic spray pyrolysis process, were characterized using x-ray diffraction (XRD), energy-dispersive spectroscopy and photoluminescence. The XRD results revealed that the films are predominantly amorphous. The weak green-red emission of Mn(2+) is enhanced through an efficient energy transfer from Ce(3+) to Mn(2+) ions. Spectroscopic data revealed that the energy transfer is nonradiative in nature and it could occur in Ce(3+) and Mn(2+) clusters through a short-range interaction mechanism. The efficiency of this transfer increases with the Mn(2+) ion concentration, so that an efficiency of about 78% is attained for a 5 at.% of MnCl(2) concentration, which makes these films interesting phosphors for the design of luminescent layers with blue, green and red emissions

Phase transition in SrxBa1-xNb2O6 ferroelectric crystals probed by raman spectroscopy

In this paper the temperature evolution of the main Raman peak at about 630 cm(-1) has been studied in order to detect the ferroelectric to paraelectric phase transition in strontium barium niobate (SrxBa1-xNb2O6) crystals with different stoichiometries (x = 0.33, 0.5 and 0.61). Both its peak wavenumber and width have been shown to be strongly dependent on temperature and display clear anomalies around the Curie temperature. The obtained results manifest the usefulness of simple unpolarized Raman spectra to probe the changes in T-c as a result of modifications in the crystal composition

Optical absorption spectroscopy of Nd3+ in the Ca3Ga2Ge3O12 laser garnet crystal

A systematic investigation of the optical absorption of the Nd3+ ion in the Ca3Ga2Ge3O12:Nd3+ garnet (CCGG:Nd) crystal is presented. An assignment of the Stark energy levels was carried out assuming a D-2 symmetry site for the Nd3+ ions in CGGG:Nd, Some relevant spectroscopy parameters for laser applications: radiative lifetime, branching ratios and quantum efficiency from the F-4(3/2) emitting state were estimated using the Judd-Ofelt theory. (C) 1999 Elsevier Science B.V. All rights reserved

Spectroscopic characterization and optical waveguide fabrication in Ce(3+), Tb(3+) and Ce(3+)/Tb(3+) doped zinc-sodium-aluminosilicate glasses

A spectroscopy investigation of Ce3+ and Tb3+ ions in sodium-zinc-aluminosilicate glasses is performed using the photoluminescence technique. Blue-white light, with x = 0.24 and y = 0.24 CIE chromaticity coordinates, is obtained for the Tb3+ singly-doped glass excited at 351 nm. When the sodium-zinc-aluminosilicate glass is co-doped with Ce3+ and Tb3+ a non-radiative energy transfer from Ce3+ to Tb3+ ions is observed upon 320 nm excitation. From an analysis of the cerium emission decay curve, the Ce3+ -> Tb3+ energy transfer microscopic parameter and efficiency are obtained. Different concentrations of Ce3+ and Tb3+ ions in the glass host gives rise to blue and blue-green emissions, with different Ce3+ coordinates. Optical waveguides were produced in the samples by Ag+-Na+ ion-exchange, and their characterization is presented. (C) 2011 Elsevier B.V. All rights reserved