| Rare earth ions doped optical glasses are important for laser, optical fiber communication, optical waveguide and optical fiber amplifier. Fluorescence of trivalent rare earth ions doped phosphate, silicate, germanate and tellurite glasses in infrared region has attracted much attention of the researchers. Among these, the infrared fluorescence of Er3+, Tm3+, Pr3+ and Ho3+ have been some in-depth studied and applied. Simultaneously, study on rare earth ions with a multi-level system like Ce3+, Sm3+, Eu3+, Tb3+, Dy3+, which offer efficient visible emissions, has become an active hot spot and attracted a considerable number of researchers, demonstrating their tempting prospects in visual display device. Borate with the advantages of high transmittance, low synthesis temperature, high rare earth ion solubility absorption and big emission cross-section can produce the effective fluorescence, when doped with Ce3+, Sm3+, Eu3+, Tb3+, Dy3+. Borate glasses doped with different rare earth ions were synthesized by high temperature melting method, namely Dy3+ doped LKZBSB luminescent glasses, Sm3+ doped LKZBSB luminescent glasses, Ce3+ doped LKZBSB luminescent glasses, and Ce3+-Sm3+ codoped LKZBSB luminescent glasses. Spectral characteristics of the obtained glass samples, such as absorption spectrum, excitation spectrum and emission spectrum in visible region were analysed, and the absolute spectral parameters were studied by using of integrating sphere test system. The followings are results this work achieved:1. Based on optical absorption, Judd-Ofelt parameters W2, W4 and W6 calculated to be Ω2=5.36′10-20 cm2, Ω4=1.46′10-20 cm2 and Ω6=1.95′10-20 cm2. And the oscillator strengths of each energy level transition, radiative lifetimes and fluorescence branch ratios of Dy3+ in LKZBSB glasses were calculated. The absolute spectral parameters, such as spectral power distribution and photon distribution were systematic characterized by using an integrating sphere, which connected to a CCD detector. Dy3+-doped LKZBSB glasses exhibit a quantum yield as high as 16.65%, indicating that the effectiveness of the warm yellowish-white luminescence in Dy3+-doped LKZBSB glasses. High quantum yield and multifarious emission channels illustrate great advantages of Dy3+-doped LKZBSB glasses in developing fiber-lighting sources, display devices, tunable visible lasers, and optical signal amplifiers.2. In the Sm3+ doped borate glass, Judd-Ofelt parameters were derived to be Ω2=3.50′10-20 cm2, Ω4=3.75′10-20 cm2 and Ω6=2.46′10-20 cm2, respectively. Then the measured and calculated oscillator strengths, the radiative transition probabilities, the fluorescence branch ratios and the radiative lifetimes of Sm3+ were calculated. Fluorescence lifetimes, quantum efficiencies, and cross-relaxation rates for 4G5/2 level of 0.2wt%, 0.4wt%, 1wt% and 2wt% Sm2O3 doped LKZBSB Sm3+ in LKZBSB glasses were also obtained. Corresponding to the 4G5/2®6HJ(J=5/2, 7/2, 9/2 and 11/2), the transition probability of spontaneous radiation were calculated to be 24.74, 129.72, 117.03 and 32.23 s-1, associated with fluorescent branching ratio were 7.17%, 37.61%, 33.93% and 9.34%. Sm3+ doped LKZBSB glass presents bright red fluorescence emission and has large cross section under UV radiation, the fluorescence quantum yield under excitation of 374 nm LED is as high as 13.29%, further confirming that efficient red light emission can be obtained in the Sm3+ doped LKZBSB glass.3. Ce3+ doped LKZBSB glasses show bright blue fluorescence, and with the introduction of Ce3+, the effective excitation wavelength range and the emission intensity of Sm3+ in LKZBSB glasses are remarkably expanded and improvedby a maximum sensitization factor of 9.02 in the UVB region. These results proved that the glass system is expected to be as ultraviolet and visible light conversion layer to improve the efficiency of solar cells, especially for the solar cells working in outer space. |
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