Enhanced 2 μm broad-band emission and NIR to visible frequency up-conversion from Ho3+/Yb3+ co-doped Bi2O3–GeO2–ZnO glasses

Abstract

In this work, a new and non-conventional oxide glass composition based on Bi2O3–GeO2–ZnO system has been formulated with an aim to realize low phonon oxide glass and elucidate its performance when co-doped with Ho3+/Yb3+ for the energy transfer based NIR emission at 2μm from Ho3+ ions under Yb3+ excitation. The glass with 1.0mol% Ho2O3 and 0.5mol% Yb2O3 has exhibited maximum energy transfer rate (3602s−1) and energy transfer efficiency (65.92%). Important radiative properties have been predicted for emission transitions of Ho3+ ions using intensity parameters derived from measured absorption spectra using standard Judd–Ofelt theory. At lower acceptor ion concentration (0.1mol%), an efficient NIR to visible up-conversion emission has been observed based on two photon absorption process which has found to be reduced significantly at higher Ho3+ concentrations with simultaneous enhancement in 2μm emission. Hence, this newly developed glass codoped with Yb3+/Ho3+ is promising glass for sensitized 2μm emission applications as broad band tunable lasers because of the combination of low phonon energy (707cm−1), high energy transfer efficiency, moderately high emission cross-section (5.33×10−21cm2) and larger effective half-width of the emission band value of 169nm.