Intense blue upconversion fluorescence of Tm3+/Yb3+-codoped bismuth tellurite glasses

Abstract

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 n1=2.0365 at 632.8nm and n2=1.9795 at 1550nm 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 Ωt(t=2，4 and 6) were obtained to be 3.90×10-20, 2.03×10-20 and 9.03×10-21cm2, 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 980nm diode laser at room temperature. Wide infrared transmission window, high refractive index and strong blue three-photon upconversion emission of Tm3+ indicate that Tm3+/Yb3+-codoped LKBBT glasses are promising upconversion optical and laser materials.