Intense blue upconversion fluorescence of TM3+/Yb3+-codoped bismuth tellurite glasses

In this paper, Tm3+/Yb3+ -codoped bismuth tellurite glasses with high refractive index have been synthesized. The refractive index of Tm3+ /Yb3+ -codoped bismuth tellurite glasses were measured by Metricon 2010 prism coupler at two wavelengths, and the values n(1) = 2.0365 at 632.8 run and n(2) = 1.9795 at 1550 nm were obtained. The absorption spectra, fluorescence spectra and infrared transmittance spectra of this glass were measured and analyzed. Based on Judd-Ofelt theory, and intensity parameters ohm(t) (t = 2, 4 and 6) were obtained to be 3. 90 x 10(-20), 2.03 x 10(-20) and 9.03 x 10(-21) cm(2), respectively. Then the radiative transition probabilities, radiative lifetimes and fluorescence branching ratio were calculated. Intense blue three-photon upconversion fluorescence and near-infrared two-photon upconversion fluorescence were investigated under the excitation of 980 run diode laser at room temperature. Wide infrared transmission window, high refractive index and strong blue three-photon upconversion emission of Tm2+ indicate that Tm3+ /Yb3+ -codoped LKBBT glasses are promising upconversion optical and laser materials.