The Er^3＋/Yb^3＋ co-doped TeO2-Nb2O5-Li2O glass is prepared by conventional melting method, and its upconversion spectra are measured. The intense green upconversion luminescence upon excitation with a 976 nm laser d...The Er^3＋/Yb^3＋ co-doped TeO2-Nb2O5-Li2O glass is prepared by conventional melting method, and its upconversion spectra are measured. The intense green upconversion luminescence upon excitation with a 976 nm laser diode is observed with the naked eyes. The dependence of luminescence intensity on the ratio of Yb^3＋/Er^3＋ is discussed in detail, and the relationship between the ratio of green luminescence intensity to red luminescence intensity and the ratio of Yb^3＋/Er^3＋ is also studied, The luminescence intensity increases with the ratio of Yb^3＋/Er^3＋ increasing. The ratio of Yb^3＋/Er^3＋ plays a more important role than the concentration of Er^3＋ in determining the upconversion luminescence intensity. The ratio of green luminescence intensity to red luminescence intensity reaches a maximum when ratio of Yb^3＋/Er^3＋ is 3. Thus the glass could be one of the potential candidates for LD pumping solid-state lasers.展开更多
The widely used energy transfer theory is a foundation of luminescence, in which the rates of Stokes and anti-Stokes processes have the same calculation formula. An improvement on the anti-Stokes energy transfer to ex...The widely used energy transfer theory is a foundation of luminescence, in which the rates of Stokes and anti-Stokes processes have the same calculation formula. An improvement on the anti-Stokes energy transfer to explain the fluorescence intensity reversal between the red and green fluorescence of Er（0.5）Yb（9.5）：FOV is reported in the present article. The range of the intensity reversal Z was measured to be 877. Dynamic processes for 16 levels were simulated. A coefficient, the improvement factor of the intensity ratio of Stokes to anti-Stokes processes in quantum Raman theory compared to classical Raman theory, is introduced to successfully describe the anti-Stokes energy transfer. A new method to calculate the distance between the rare earth ions, which is critical for the energy transfer calculation, is proposed. The validity of these important improvements is also proved by experiment.展开更多
An iterative method is used to find the values of the Hamiltonian parameters for Yb^3＋ in a given low-symmetry crys- talline site. Samples of Yb^3＋ ：RETaO4 （RE = Gd, Y, and Sc） were prepared and their structures ...An iterative method is used to find the values of the Hamiltonian parameters for Yb^3＋ in a given low-symmetry crys- talline site. Samples of Yb^3＋ ：RETaO4 （RE = Gd, Y, and Sc） were prepared and their structures were determined. Based on the obtained structural data, their orbital-spin parameters and crystal field parameters were fitted by the superposition model （SM）. Using the crystal field parameters obtained by the SM fitting as the initial parameters, the Hamiltonian parameters were fitted iteratively. The calculated and experimental energy levels for Yb^3＋：RETaO4 are consistent, and the maximal mean-root-square deviation is only 2.84 cm^- 1, indicating that the method is effective to determine the Hamiltonian parameters of Yb^3＋ in low-symmetry crystalline sites.展开更多
In the present study, we investigated the effect of cerium and erbium doping of the zirconium dioxide matrix. We synthesized doped samples using hydrothermal process. The amounts of dopant used were 0.5%, 1% and 5% mo...In the present study, we investigated the effect of cerium and erbium doping of the zirconium dioxide matrix. We synthesized doped samples using hydrothermal process. The amounts of dopant used were 0.5%, 1% and 5% molar(rare earth oxide over zirconium dioxide) respectively. The samples have been studied via X-ray Diffraction measurements for the structural characterization. UV visible diffuse reflectance was used for the optical analysis, Brunauer-Emmett-Teller(BET) model for the measurement of the surface area. Finally the samples have been analysed via electron paramagnetic resonance(EPR) for the electronic characterization. Then we tested the new synthetized materials to determine their photocatalytic activity in the reaction of degradation of methylene blue performed under irradiation by diodes(LEDs) emitting exclusively visible light.展开更多
The Yb：YAG is an excellent high-average power and ultra-short pulse laser crystal. Transition intensity parameters A（tp）~k and Huang–Rhys factors are fitted to its emission spectrum by the full-profile fitting met...The Yb：YAG is an excellent high-average power and ultra-short pulse laser crystal. Transition intensity parameters A（tp）~k and Huang–Rhys factors are fitted to its emission spectrum by the full-profile fitting method. Calculated results indicate that the emission spectrum of Yb：YAG at cryogenic temperature consists of three pure electron state transitions and two phononassisted transitions, one vibronic transition releases one-phonon of 3 cm^（-1）, and the other vibronic transition absorbs onephonon of 22 cm^（-1）. At 300 K, the phonon assisted transition of 3 cm^（-1） turns into two-or more-phonon assisted transitions.The procedure absorbing phonon can reduce the thermal load of Yb：YAG and improve the laser efficiency, which may be one of the reasons why Yb：YAG has excellent performance. The emission bands of Yb：YAG are broadened thermally, and the peak values decrease by several times. The emission cross sections of Yb：YAG determined by Fuchtbauer–Ladenburg（F–L） formula are remarkably different from those calculated with A（tp）~k, which indicates that it is necessary for a laser material to determine its transition intensity parameters A（tp）~kin order to reasonably evaluate the laser performance.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 60307004） and the Science and Technology Program of Guangzhou, Guangdong province, China （Grant No 2004Z2-D0131）.
文摘The Er^3＋/Yb^3＋ co-doped TeO2-Nb2O5-Li2O glass is prepared by conventional melting method, and its upconversion spectra are measured. The intense green upconversion luminescence upon excitation with a 976 nm laser diode is observed with the naked eyes. The dependence of luminescence intensity on the ratio of Yb^3＋/Er^3＋ is discussed in detail, and the relationship between the ratio of green luminescence intensity to red luminescence intensity and the ratio of Yb^3＋/Er^3＋ is also studied, The luminescence intensity increases with the ratio of Yb^3＋/Er^3＋ increasing. The ratio of Yb^3＋/Er^3＋ plays a more important role than the concentration of Er^3＋ in determining the upconversion luminescence intensity. The ratio of green luminescence intensity to red luminescence intensity reaches a maximum when ratio of Yb^3＋/Er^3＋ is 3. Thus the glass could be one of the potential candidates for LD pumping solid-state lasers.
基金Project supported by the National Natural Science Foundation of China (Grant No 10674019)
文摘The widely used energy transfer theory is a foundation of luminescence, in which the rates of Stokes and anti-Stokes processes have the same calculation formula. An improvement on the anti-Stokes energy transfer to explain the fluorescence intensity reversal between the red and green fluorescence of Er（0.5）Yb（9.5）：FOV is reported in the present article. The range of the intensity reversal Z was measured to be 877. Dynamic processes for 16 levels were simulated. A coefficient, the improvement factor of the intensity ratio of Stokes to anti-Stokes processes in quantum Raman theory compared to classical Raman theory, is introduced to successfully describe the anti-Stokes energy transfer. A new method to calculate the distance between the rare earth ions, which is critical for the energy transfer calculation, is proposed. The validity of these important improvements is also proved by experiment.
基金supported by the National Natural Science Foundation of China (Grant Nos. 90922003,51172236,and 50872135)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. YYYJ-1002)
文摘An iterative method is used to find the values of the Hamiltonian parameters for Yb^3＋ in a given low-symmetry crys- talline site. Samples of Yb^3＋ ：RETaO4 （RE = Gd, Y, and Sc） were prepared and their structures were determined. Based on the obtained structural data, their orbital-spin parameters and crystal field parameters were fitted by the superposition model （SM）. Using the crystal field parameters obtained by the SM fitting as the initial parameters, the Hamiltonian parameters were fitted iteratively. The calculated and experimental energy levels for Yb^3＋：RETaO4 are consistent, and the maximal mean-root-square deviation is only 2.84 cm^- 1, indicating that the method is effective to determine the Hamiltonian parameters of Yb^3＋ in low-symmetry crystalline sites.
基金supported by the CARIPLO Foundation with the Advanced Materials Grant 2013 "Development of second generation photocatalysts for energy and environment"the Local Funding of the University of Torino call_2014_L2_126
文摘In the present study, we investigated the effect of cerium and erbium doping of the zirconium dioxide matrix. We synthesized doped samples using hydrothermal process. The amounts of dopant used were 0.5%, 1% and 5% molar(rare earth oxide over zirconium dioxide) respectively. The samples have been studied via X-ray Diffraction measurements for the structural characterization. UV visible diffuse reflectance was used for the optical analysis, Brunauer-Emmett-Teller(BET) model for the measurement of the surface area. Finally the samples have been analysed via electron paramagnetic resonance(EPR) for the electronic characterization. Then we tested the new synthetized materials to determine their photocatalytic activity in the reaction of degradation of methylene blue performed under irradiation by diodes(LEDs) emitting exclusively visible light.
基金supported by the National Natural Science Foundation of China(Grant Nos.61405206,51502292,and 51702322)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant Nos.CXJJ-16M251 and CXJJ-15M055)the National Key Research and Development Program of China(Grant No.2016YFB0402101)
文摘The Yb：YAG is an excellent high-average power and ultra-short pulse laser crystal. Transition intensity parameters A（tp）~k and Huang–Rhys factors are fitted to its emission spectrum by the full-profile fitting method. Calculated results indicate that the emission spectrum of Yb：YAG at cryogenic temperature consists of three pure electron state transitions and two phononassisted transitions, one vibronic transition releases one-phonon of 3 cm^（-1）, and the other vibronic transition absorbs onephonon of 22 cm^（-1）. At 300 K, the phonon assisted transition of 3 cm^（-1） turns into two-or more-phonon assisted transitions.The procedure absorbing phonon can reduce the thermal load of Yb：YAG and improve the laser efficiency, which may be one of the reasons why Yb：YAG has excellent performance. The emission bands of Yb：YAG are broadened thermally, and the peak values decrease by several times. The emission cross sections of Yb：YAG determined by Fuchtbauer–Ladenburg（F–L） formula are remarkably different from those calculated with A（tp）~k, which indicates that it is necessary for a laser material to determine its transition intensity parameters A（tp）~kin order to reasonably evaluate the laser performance.
