Hongtao Sun

Shanghai Institute of Optics and Fine Mechanics, CAS, Shanghai, Shanghai Shi, China

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Publications (40)48.09 Total impact

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    ABSTRACT: Er3+, Yb3+ and Tm3+ codoped fluorophosphate glasses emitting blue, green and red upconversion luminescence at 970 nm laser diode excitation were studied. It was shown that Tm3+ behaves as the sensitizer to Er3+ for the green upconversion luminescence through the energy transfer process: Tm3+:3H4+Er3+:4I 15/2-->Er3+:4I 9/2+Tm3+:3H6, and for the red upconversion luminescence through the energy transfer process: Tm3+:3F4+Er3+:4I 11/2-->Tm3+:3H6+Er3+:4F 9/2. Moreover, Er3+ acts as quenching center for the blue upconversion luminescence of Tm3+. The sensitization of Tm3+ to Er3+ depends on the concentration of Yb3+. The intensity of blue, green and red emissions can be changed by adjusting the concentrations of the three kinds of rare earth ions. This research may provide useful information for the development of high color and spatial resolution devices and white light simulation.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 11/2007; 68(3):531-5. · 1.98 Impact Factor
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    ABSTRACT: Er3+/Tm3+/Yb3+ tridoped oxyfluoride glass ceramics was synthesized in a general way. Under 980 nm LD pumping, intense red, green and blue upconversion was obtained. And with those primary colors, multicolor luminescence was observed in oxyfluoride glass ceramics with various dopant concentrations. The red and green upconversion is consistent with 4F9/2 → 4I15/2 and 2H11/2, 4S3/2 → 4I15/2 transition of Er3+ respectively. While the blue upconversion originates from 1G4 → 3H6 transition of Tm3+. This is similar to that in Er3+/Yb3+ and/or Tm3+/Yb3+ codoped glass ceramics. However the upconversion of Tm3+ is enhanced by the energy transfer between Er3+ and Tm3+.
    Materials Letters. 01/2007; 61:2200-2203.
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    ABSTRACT: The sensitization mechanisms of Yb3+ to Tm3+ for the blue upconversion luminescence in fluorophosphate glass were studied. Two different mechanisms exist in the sensitization. One is the sequential sensitization that Tm3+ is excited from 3H6 to 1G4 through absorbing three photons transferred from Yb3+ one by one. Another is the cooperative sensitization that two Yb3+ ions form a couple cluster firstly, and then the couple cluster Yb3+ ions transfer their energy to Tm3+ and excite it to 1G4. With the increment of the concentration of Yb3+ ions, the sequential sensitization becomes weak and the cooperative sensitization becomes intense, and the transformation trend of sensitization mechanism with the increment of Yb3+ concentration can be clarified by the introduction of Tb3+ ions in the glass.
    Materials Letters - MATER LETT. 01/2007; 61(2):470-472.
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    ABSTRACT: The thermal stability and structure of RF–RF2–AlF3–Al(PO3)3 fluorophosphate glasses were investigated. Analyses of infrared absorbance spectra and Raman spectra reveal that with increasing number of alkali and alkaline earth fluoride components, the sum of POP bond and OPO bond increases and glass network is strengthened. Consequently, the inhibition to nucleation and crystallization processes is improved, which is proved by the increment of thermal stability factors ΔT and S determined by differential scanning calorimetry. In addition, it was found that LiF has poor ability to form glass in univalent alkali fluorides and MgF2 has comparative strong ability to form glass in bivalent alkaline earth fluorides.
    Materials Chemistry and Physics. 07/2006; 98(1):154–158.
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    ABSTRACT: Er3+/Yb3+-codoped novel oxyfluoride bismuth–germanium glass was prepared and its up-conversion fluorescence property under 975 nm excitation has been studied. Intense green and weak red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2, respectively, were observed at room temperature. The possible up-conversion mechanism was also evaluated. The optimal Yb3+–Er3+ concentration ratio is found based on the direct lifetime measurements of excited levels for Er3+ ion. The structure of this novel oxyfluoride bismuth–germanium glass has been investigated by peak-deconvolution of FT-Raman spectrum, and the structural information was obtained from the peak wavenumbers. This novel oxyfluoride bismuth–germanium glass with relatively lower maximum phonon energy (∼731 cm−1) can be used as potential host material for up-conversion lasers.
    Optical Materials. 03/2006;
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    ABSTRACT: In a three-components fluorophosphate glass system, the introduction of H3BO3 brings some valuable influence to the spectroscopic and thermal properties of the glasses. With H3BO3 increases from 2 to 20mol%, Ω6, Sed4I13/2, FWHM, Tg and fluorescence lifetime change from 3.21×10−20cm2, 1.77×10−20cm2, 45nm, 480°C and 8.8ms to 4.66×10−20cm2, 2.11×10−20cm2, 50nm, 541°C and 7.4ms, respectively. σabs, σemi, FWHM×τf×σemi has a maximum when H3BO3 is 11mol%. Tg and Tx−Tg increases with H3BO3 introduction. Results showed that in fluorophosphate glasses, proper amount of B2O3 can be used as a modifier to suppress upconversion and improve spectroscopic properties, broadband property and crystallization stability of the glasses while keeps the fluorescence lifetime relatively high.
    Journal of Luminescence 01/2006; 117(1):46-52. · 2.14 Impact Factor
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    ABSTRACT: Tm3+/Yb3+-codoped heavy metal oxide-halide glasses have been synthesized by conventional melting and quenching method. Structural properties were obtained based on the Raman spectra, indicating that halide ion has an important influence on the phonon density and maximum phonon energy of host glasses. Intense blue and weak red emissions centered at 477 and 650 nm, corresponding to the transitions 1G4-->3H6 and 1G4-->3H4, respectively, were observed at room temperature. The possible up-conversion mechanisms are discussed and estimated. With increasing halide content, the up-conversion luminescence intensity and blue luminescence lifetimes of Tm3+ ion increase notably. Our results show that with the substitution of halide ion for oxygen ion, the decrease of phonon density and maximum phonon energy of host glasses both contribute to the enhanced up-conversion emissions.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 01/2006; 63(1):149-53. · 1.98 Impact Factor
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    ABSTRACT: 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 Ω2 parameter decreases, while the Ω6 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 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2, respectively, were simultaneously observed at room temperature. With increasing PbF2 content, the intensity of red (657 nm) emissions increases significantly, while that of the green (525 and 546 nm) emission increases slightly. The results indicate that PbF2 has more influence on the red (657 nm) emission than the green (525 and 546 nm) emissions in oxyfluoride germanate glasses. The possible upconversion luminescence mechanisms have also been estimated and discussed.
    Journal of Luminescence 01/2006; 117(2):179-186. · 2.14 Impact Factor
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    ABSTRACT: Fluorophosphate glasses codoped with Tm3+ and Yb3+ were prepared and their thermal stability, phonon states, and upconversion properties were studied. It is found that the increment of phosphate content is good for the thermal stability but increases the phonon density of states. However, the phonon density of states of these fluorophosphate glasses is very low due to the low phosphate content in their composition. The upconversion luminescence spectra were measured under excitation of 970 nm laser diode, and the intense blue (476 nm) and near infrared (794 nm) emission were simultaneous obtained at room temperature. The sensitizing mechanisms of Yb3+ to Tm3+ for blue and red emission contain both sequential and cooperative sensitization. The near infrared emission is a two-photon upconversion process. These researches suggest that when the phosphate content in the composition is low enough, fluorophosphate glass can be suitable host material of Tm3+ codoped with Yb3+ for blue and near infrared upconversion luminescence.
    Materials Letters - MATER LETT. 01/2006; 60(15):1783-1785.
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    ABSTRACT: Yb3+Er3+-codoped chloride-modified germanate-bismuth-lead glasses have been synthesized by the conventional melting and quenching method. Structural and thermal stability properties have been obtained on the basis of the Raman spectra and differential thermal analysis, which indicate that the PbCl2 addition has an important influence on the phonon density of states, maximum phonon energy, and thermal stability of host glasses. The Judd-Ofelt intensity parameters and quantum efficiencies were calculated on the basis of the Judd-Ofelt theory and lifetime measurements. For the 1.53 μm emission band, the full widths at the half-maximum increase and peak wavelengths are blueshifted with increasing PbCl2 content. Moreover, the effect of the PbCl2 addition on the phonon density of states, OH- content, and upconversion luminescence has been discussed and evaluated. Our results reveal that, with increasing PbCl2 content, the decrease of phonon density and OH- content contributes more to the enhanced upconversion emissions than that of maximum phonon energy.
    Journal of the Optical Society of America B 12/2005; 22(12):2601-2609. · 2.21 Impact Factor
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    ABSTRACT: Ytterbium-sensitized erbium-doped oxide-halide tellurite and germanate-niobic-lead glasses have been synthesized by conventional melting method. Intense green and red emissions centered at 525, 546 and 657 nm, corresponding to the transitions 2H11/2-->4I15/2, 4S3/2-->4I15/2 and 4F9/2-->4I15/2, respectively, were simultaneously observed at room temperature in these glasses. The quadratic dependence of the 525, 546 and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs. Tellurite glass showed a weaker up-conversion emission than germanate-niobic-lead glass, which is inconsistent with the prediction from the difference of maximum phonon energy between tellurite and germanate-niobic-lead glasses. In this paper, Raman spectroscopy was employed to investigate the origin of the difference in up-conversion luminescence in the two glasses. Compared with phonon side-band spectroscopy, Raman spectroscopy extracts more information including both phonon energy and phonon density. Our results reveal that the phonon density and the maximum phonon energy of host glasses are both important factors in determining the up-conversion efficiency.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 12/2005; 62(4-5):1000-3. · 1.98 Impact Factor
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    ABSTRACT: Effect of fluoride ions introduction on structural, OH− content and up-conversion luminescence properties in Er3+-doped heavy metal oxide glasses have been investigated. Structure was investigated, indicating that fluoride has an important influence on the phonon density, maximum phonon energy of host glasses. With increasing fluoride content, the up-conversion luminescence intensity and quantum efficiencies increase notably, which could not be explained only by the maximum phonon energy change of host glasses. Our results show that, with the introduction of PbF2, the decrease of phonon density and OH− content contributes more to the enhanced up-conversion emissions than that of maximum phonon energy.
    Chemical Physics Letters 06/2005; 408:179-185. · 2.15 Impact Factor
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    ABSTRACT: 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 nm, corresponding to the transitions 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2, 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 4I11/2 level is supposed to serve as the intermediate state responsible for the upconversion processes.
    Journal of Alloys and Compounds. 04/2005; 391(s 1–2):198–201.
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    ABSTRACT: A systematic investigation on glass formation in the PbF2–InF3–BaHPO4 ternary system has been carried out. These glasses have characterized by IR spectra, Raman spectra and differential thermal analysis. The results show that the structure of these glasses is mainly affected by BaHPO4 and InF3 contents. With decreasing BaHPO4 content, the glass structure gradually transforms from metaphosphate to polyphosphate. When InF3 content is low, it mainly acts as network modifier, when its content is high; it enters glass matrix and forms In(O,F)6 groups connecting the polymerized phosphorus oxygen species. PbF2 mainly acts as network modifier in this system. Systematic variations of the glass transition temperature and the thermal stability index agree well with these results. The most stable glass with ΔT = 230 °C and S = 21.79 K is obtained.
    ChemInform 04/2005; 391(s 1–2):151–155.
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    ABSTRACT: Infrared-to-visible upconversion fluorescence of Er(3+)/Yb(3+) co-doped lithium-strontium-lead-bismuth (LSPB) glasses for developing potential upconversion lasers has been studied under 975-nm excitation. Based on the results of energy transfer efficiency and upconversion spectra, the optimal Yb(3+)-Er(3+) concentration ratio is found to be 5:1. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H_(11/2)-->4I_(15/2), 4S_(3/2)-->4I_(15/2), and 4F_(9/2)-->4I_(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 high-populated 4I_(11/2) level is supposed to serve as the intermediate state responsible for the upconversion processes. The intense upconversion luminescence of Er(3+)/Yb(3+) co-doped LSPB glasses may be a potentially useful material for developing upconversion optical devices.
    Chinese Optics Letters 02/2005; 3(2):103-106. · 1.07 Impact Factor
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    ABSTRACT: Er3+-doped strontium lead bismuth glass for developing upconversion lasers has been fabricated and characterized. The Judd–Ofelt intensity parameters Ωt (t = 2, 4, 6), calculated based on the experimental absorption spectrum and Judd–Ofelt theory, were found to be Ω2 = 2.95 × 10−20, Ω4 = 0.91 × 10−20, and Ω6 = 0.36 × 10−20 cm2. Under 975 nm excitation, intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2, respectively, were observed. The upconversion mechanisms are discussed based on 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 4I11/2 level is supposed to serve as the intermediate state responsible for the upconversion processes.
    Journal of Non-Crystalline Solids 02/2005; · 1.72 Impact Factor
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    ABSTRACT: For the first time, effect of halide ions (F−, Cl−, Br−, and I−) introduction on structure, thermal stability, and upconversion fluorescence in Er3+/Yb3+-codoped oxide–halide germanium–bismuth glasses has been systematically investigated. The results show that halide ions modified germanium–bismuth glasses have lower maximum phonon energy and phonon density, worse thermal stability, longer measured lifetimes of 4I11/2 level, and stronger upconversion emission than germanium–bismuth glass. All these results indicate that halide ions play an important role in the formation of glass network, and have an important influence on the upconversion luminescence. The possible upconversion mechanisms of Er3+ ion are also evaluated.
    Solid State Communications 01/2005; · 1.53 Impact Factor
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    ABSTRACT: Thermal stability, Raman spectra and blue upconversion luminescence properties of Tm3+/Yb3+-codoped halide modified tellurite glasses have been studied. The results showed that the mixed halide modified tellurite glass (TFCB) has the best thermal stability, the lowest phonon energies and the strongest upconversion emissions. The effect of halide on upconversion intensity is observed and discussed and possible upconversion mechanisms are evaluated. The intense blue upconversion luminescence of Tm3+ in TFCB glass may be a potentially useful material for developing upconversion optical devices.
    Solid State Communications 01/2005; · 1.53 Impact Factor
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    ABSTRACT: Er3+-doped lithium–barium–lead–bismuth glass for developing upconversion lasers has been fabricated and characterized. The Judd–Ofelt intensity parameters Ωt (t = 2, 4, 6), calculated based on the experimental absorption spectrum and Judd–Ofelt theory, were found to be Ω2 = 3.05 × 10−20 cm2, Ω4 = 0.95 × 10−20 cm2, and Ω6 = 0.39 × 10−20 cm2. Under 975 nm excitation, intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2, respectively, were observed at room temperature. The upconversion mechanisms are discussed based on 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 4I11/2 level is supposed to serve as the intermediate state responsible for the intense upconversion processes. The intense upconversion luminescence of Er3+-doped lithium–barium–lead–bismuth glass may be a potentially useful material for developing upconversion optical devices.
    Materials Science and Engineering: A. 01/2005;
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    ABSTRACT: 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 657nm, corresponding to the transitions 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2, respectively, were observed at room temperature. With increasing PbCl2 content, the intensity of green (525 and 546nm) emissions increases significantly, while the red (657nm) 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.
    Solid State Communications 01/2005; 133(12):753-757. · 1.53 Impact Factor

Publication Stats

117 Citations
48.09 Total Impact Points

Institutions

  • 2005–2007
    • Shanghai Institute of Optics and Fine Mechanics, CAS
      Shanghai, Shanghai Shi, China
    • University of Jinan (Jinan, China)
      Chi-nan-shih, Shandong Sheng, China
    • China Jiliang University
      Shanghai, Shanghai Shi, China
  • 2004–2007
    • Chinese Academy of Sciences
      • Anhui Institute of Optics and Fine Mechanics
      Beijing, Beijing Shi, China
  • 2004–2006
    • Northeast Institute of Geography and Agroecology
      • Anhui Institute of Optics and Fine Mechanics
      Beijing, Beijing Shi, China