Optical properties and upconversion in Yb3+—Tm3+ co-doped oxyfluoride glasses and glass ceramics

Abstract

Optical spectroscopy of Yb3+ and Tm3+ doped silica based oxyfluoride glass ceramics has been investigated and compared with results for the precursor glasses. Room-temperature absorption, luminescence and upconversion spectra (480, 700 and 800 nm) after infrared excitation at 975 nm have been recorded. From optical absorption spectra, the oscillator strengths have been obtained and used to calculate the Judd-Ofelt parameters. Changes in the spectra of the Yb3+ and Tm3+ ions indicate that the ceramming process modifies the environment of these ions. The dependence of the upconverted emissions on excitation intensity has been measured and from the results obtained the mechanisms involved in the upconversion processes are analysed in the different samples.