Efficient frequency upconversion emission in Er3+-doped novel strontium lead bismuth glass

Er3+ -doped strontium lead bismuth glass for developing upconversion lasers has been fabricated and characterized. The Judd-Ofelt intensity parameters Omega(1) (t = 2,4,6), calculated based on the experimental absorption spectrum and Judd-Ofelt theory, were found to be Omega(2) = 2.95 x 10(-20), Omega(4) = 0-91 X 10(-20), and Omega(6) = 0.36 x 10(-20) cm(2). Under 975 nm excitation, intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions H-2(11/2) --> I-4(15/2), S-4(3/2) I-4(15/2), and F-4(9/2) --> I-4(15/2) respectively were observed. The upconversion mechanisms are discussed based oil the energy matching and quadratic dependence on excitation power, and the dominant mechanisms are excited state absorption and energy transfer upconversion for the green and red emissions. The long-lived I-4(11/2) level is supposed to serve as the intermediate state responsible for the upconversion processes. (C) 2004 Published by Elsevier B.V.

Energy-transfer frequency upconversion in neodymium-sensitized praseodymium-doped PbGeO3-PbF2-CdF2 glass excited at 810 nm

Visible frequency upconversion emission through resonant energy-transfer involving neodymium and praseodymium ions in PbGeO3-PbF2-CdF2 glass excited by a semiconductor laser at 8 10 nm is investigated. Luminescence emission centered around 485, 530, 610, and 645 nm, which correspond to the P-3(0) -> H-3(4), P-3(1) + I-1(6) -> H-3(5), P-3(0) -> H-3(6) and P-1(0) -> F-3(2) transitions of praseodymium ions, respectively, are observed. The upconversion excitation of the Pr3+ ions excited-state emitting levels was accomplished by means of an ion-pair interaction involving ground-state absorption, multiphonon relaxation, and excited-state absorption of pump photons at 8 10 nm by the Nd3+ (I-4(9/2) -> H-2(9/2), F-4(5/2); F-4(3/2) -> P-2(1/2)) and direct energy-transfer to Pr3+ ((4)G(11/2) + K-2(11/2), H-3(4) -> I-4(9/2), P-3(1) + I-1(6)). The dependence of the upconversion emission intensity upon the excitation power, and neodymium concentration are also examined. (c) 2004 Elsevier B.V. All rights reserved.

Intense frequency upconversion fluorescence emission of Er3+/Yb3+-codoped oxychloride germanate glass

Structural and frequency upconversion fluorescence properties of Er3+/Yb3+-codoped oxychloride germanate glasses have been investigated. The Raman spectrum investigation indicates that PbCl2 plays an important role in the formation of glass network and has an important influence on the upconversion luminescence. Intense green and red emissions centered at 525, 546 and 657 nm, corresponding to the transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2), respectively, were observed at room temperature. The possible upconversion mechanism was also estimated and evaluated. Intense upconversion luminescence indicates that Er3+/Yb3+-codoped oxychloride germanate glass is a promising laser material. (c) 2005 Elsevier B.V. All rights reserved.

Frequency upconversion fluorescence emission of Er3+-doped oxychloride germanate glass

Frequency upconversion fluorescence property of Er3+-doped oxychloride germanate glass is investigated. Intense green and red emissions centred at 525, 546, and 657nm, corresponding to the transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> 4I(15/2), and F-4(9/2) -> I-4(15/2), respectively, were simultaneously observed at room temperature. The quadratic dependence of the 525, 546, and 657nm emissions on excitation power indicates that a two-photon absorption process occurs under 975nm laser diode (LD) excitation. The Raman spectrum investigation indicates that oxychloride germanate glass has the maximum phonon energy at similar to 805 cm(-1). The thermal stability of this oxychloride germanate glass is evaluated by differential scanning calorimetry, and thermal stability factor Delta T (Delta T = T-x-T-g) is 187 degrees C. Intense upconversion luminescence and good thermal stability indicate that Er3+-doped oxychloride germanate glass is a promising upconversion laser material.

1.5 mu m emission and infrared-to-visible frequency upconversion in Er+3/Yb+3-doped phosphoniobate glasses

Sodium phosphoniobate glasses with the composition (mol%) 75NaPO(3)-25Nb(2)O(5) and containing 2 mol% Yb3+ and x mol% Er3+ (0.01 <= x <= 2) were prepared using the conventional melting/casting process. Er3+ emission at 1.5 mu m and infrared-to-visible upconversion emission, upon excitation at 976 nm, are evaluated as a function of the Er3+ concentration. For the lowest Er3+ content, 1.5 mu m emission quantum efficiency was 90%. Increasing the Er3+ concentration up to 2 mol%, the emission quantum efficiency was observed to decrease to 37% due to concentration quenching. The green and red upconversion emission intensity ratio was studied as a function of Yb3+ co-doping and the Er3+-Er3+ energy transfer processes. (c) 2006 Elsevier B.V. All rights reserved.

Frequency upconversion properties of Er3+/Yb3+-codoped lead-germanium-bismuth oxide glasses

The frequency upconversion properties of Er3+/Yb3+-codoped heavy metal oxide lead-germanium-bismuth oxide glasses under 975 mn excitation are investigated. Intense green and red emission bands centered at 536, 556 and 672 run, corresponding to the H-2(1/2) --> I-4(15/2), S-4(3/2) --> I-4(15/2) and F-4(9/2) -->I-4(15/2) transitions of Er3+, respectively, were simultaneously observed at room temperature. The influences of PbO on upconversion intensity for the green (536 and 556 nm) and red (672 nm) emissions were compared and discussed. The optimized rare earth doping ratio of Er3+ and Yb3+, is 1:5 for these glasses, which results in the stronger upconversion fluorescence intensities. The dependence of intensities of upconversion emission on excitation power and possible upconversion mechanisms were evaluated and analyzed. The structure of glass has been investigated by means of infrared (IR) spectral analysis. The results indicate that the Er3+/Yb3+-codoped heavy metal oxide lead-germanium-bismuth oxide glasses may be a potential materials for developing upconversion fiber optic devices. (C) 2006 Published by Elsevier Ltd.

Intense frequency upconversion luminescence in Yb3+/Tm3+-codoped oxychloride germanate glasses

Yb3+/Tm3+-codoped oxychloride germanate glasses for developing potential upconversion lasers have been fabricated and characterized. Structural properties were obtained based on the Raman spectra analysis, indicating that PbCl2 plays an important role in the formation of glass network and has an important influence on the maximum phonon energies of host glasses. Intense blue and weak red emissions centered at 477 and 650 nm, corresponding to the transitions (1)G(4) -> H-3(6) and (1)G(4) -> H-3(4), respectively, were observed at room temperature. With increasing PbCl2 content, the intensity of blue (477 nm) emission increases significantly, while the red (650 nm) emission increases slowly. The results indicate that PbCl2 has more influence on the blue emissions than the red emission in oxychloride germanate glasses. The possible upconversion mechanisms are discussed and estimated. Intense blue upconversion luminescence indicates that these oxychloride germanate glasses can be used as potential host material for upconversion lasers. C (c) 2005 Springer Science + Business Media, Inc.

Host dependent thermal stability and frequency upconversion of Er3+-doped heavy metal oxyfluoride germanate glasses

The upconversion properties of Er3+-doped heavy metal oxyfluoride germanate glasses under 975 nm excitation have been investigated. The intense green (551 and 529 nm) and relatively weak red (657 nm) emissions corresponding to the transitions S-4(3/2) -> I-4(15/2), H-2(11/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2), respectively, were simultaneously observed at room temperature. The content of PbF2 has an important influence on the upconversion luminescence emission. With increasing content of PbF2, the intensities of green (529 nm) and red (657 nm) emissions increase slightly, while the green emission (551 nm) increases markedly. These results suggest that PbF2 has an influence on the green (551 nm) emission more than on the green (529 nm) and red (657 nm) emissions.

Host dependent frequency upconversion of Er3+-doped oxyfluoride germanate glass

Er3+-doped oxyfluoride germanate glasses have been synthesized by the conventional melting and quenching method. The Judd-Ofelt intensity parameters were calculated based on the Judd-Ofelt theory and absorption spectra measurements. With the substitution of PbF2 for PbO, the Omega(2) parameter decreases, while the Omega(6) parameter increases. These change trends indicate that fluoride anions come to coordinate erbium cations and the covalency of the Er-O bond decreases. Structural and thermal stability properties were obtained by Raman spectra and differential thermal analysis, indicating that PbF2 plays an important role in the formation of glass network and has an important influence on the maximum phonon energy and thermal stability of host glasses. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2), respectively, were simultaneously observed at room temperature. With increasing PbF2 content, the intensity of red (657nm) emissions increases significantly, while that of the green (525 and 546nm) emission increases slightly. The results indicate that PbF, has more influence on the red (657nm) emission than the green (525 and 546nm) emissions in oxyfluoride germanate glasses. The possible upconversion luminescence mechanisms have also been estimated and discussed. (c) 2005 Elsevier B.V. All rights reserved.

Composition dependent frequency upconversion luminescence in Er3+-doped oxychloride germanate glasses

Er3+ -doped oxychloride germanate glasses have been synthesized by conventional melting and quenching method. Structural and thermal stability properties were obtained based on the Raman spectra and differential thermal analysis, indicating that PbCl2 plays an important role in the formation of glass network and has an important influence on the maximum phonon energy and thermal stability of host glasses. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2), respectively, were observed at room temperature. With increasing PbCl2 content, the intensity of green (525 and 546 nm) emissions increases significantly, while the red (657 nm) emission increases slowly. The results indicate that PbCl2 has more influence on the green emissions than the red emission in oxychloride germanate glasses. The possible upconversion luminescence mechanisms has also been estimated and discussed. (c) 2005 Elsevier Ltd. All rights reserved.

Intense frequency upconversion fluorescence of Er3+/Yb3+-codoped novel potassium-barium-strontium-lead-bismuth glasses

Er3+/Yb3+-codoped potassium-barium-strontium-lead-bismuth glasses for developing potential upconversion lasers have been fabricated and characterized. Based on the results of energy transfer efficiency, the optimal Yb3+/Er3+ concentration ratio is found to be 5:1. Intense green and red emissions centered at 525, 546, and 657 run, corresponding to the transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2), respectively, were observed. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation. The long-lived I-4(11/2) level is supposed to serve as the intermediate state responsible for the upconversion processes. (c) 2004 Elsevier B.V. All rights reserved.

Color tunability of intense upconversion emission from Er3+-Yb3+ co-doped SiO2-Ta2O5 glass ceramic planar waveguides

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Optical spectroscopy and frequency upconversion properties of Tm3+ doped tungstate fluorophosphate glasses

Tungstate fluorophosphate glasses of good optical quality were synthesized by fusion of the components and casting under air atmosphere. The absorption spectra from near-infrared to visible were obtained and the Judd-Ofelt parameters determined from the absorption bands. Transition probabilities, excited state lifetimes and transition branching ratios, were, determined from the measurements. Pumping with a 354.7 nm beam from a pulsed laser. resulted in emission at 450 nm. due to transition D-1(2)-->F-3(4) in Tm3+ ions and a broadband emission centered at approximate to 550 nm attributed to the glass matrix. When pumping at 650 nm, two emission bands at 450 nm (D-1(2)-->F-3(4)) and at 790 nm (H-3(4)-->H-3(6)) were observed. Excitation spectra were also obtained in order to understand the origin of both emissions. Theoretical and experimental lifetimes were determined and,the results were explained in terms of multiphonon relaxation. (C) 2003 American Institute of Physics.

Red-green-blue upconversion emission and energy-transfer between Tm3+ and Er3+ ions in tellurite glasses excited at 1.064 mu m

Red, green, and blue emission through frequency upconversion and energy-transfer processes in tellurite glasses doped with Tm3+ and Er3+ excited at 1.064 mum is investigated. The Tm3+/Er3+-codoped samples produced intense upconversion emission signals at around 480, 530, 550 and 660 nm. The 480 nm blue emission was originated from the (1)G(4)-->H-3(6) transition of the Tm3+ ions excited by a multiphoton stepwise phonon-assisted excited-state absorption process. The 5 30, 5 50 nm green and 660 mn red upconversion luminescences were identified as originating from the H-2(11/2), S-4(3/2) --> I-4(15/2) and F-4(9/2) --> I-4(15/2) transitions of the Er3+ ions, respectively, populated via efficient cross-relaxation processes and excited-state absorption. White light generation employing a single infrared excitation source is also examined. (C) 2003 Elsevier B.V. (USA). All rights reserved.

Temperature investigation of infrared-to-visible frequency upconversion in erbium-doped tellurite glasses excited at 1540 nm

Temperature investigation of infrared-to-visible frequency upconversion in erbium-doped tellurite glasses excited by CW laser radiation at 1540 nm and under cryogenic temperatures is reported. Intense upconversion emission signals around 530, 550 and 660 nm corresponding to the H-2(11/2), S-4(3/2), and F-4(9/2) transitions to the I-4(15/2) ground state were generated and studied as a function of the laser intensity and temperature. The upconversion excitation mechanism of the Er3+ ions emitting energy levels was accomplished via stepwise multiphoton absorption. The green upconversion luminescence exhibited a fivefold intensity enhancement when the temperature of the sample was varied in the range between 5 and 300 K. A maximum green upconversion intensity was attained around 120 K and a steady decreasing behavior for higher temperatures up to 300 K was observed. A model based upon conventional rate equations was used to model the observed temperature evolution of the upconversion luminescence. (C) 2002 Elsevier B.V. B.V. All rights reserved.