Local Symmetry Structure And The Ambient Temperature On Rare-earth Doped Transparent Nano-glass-ceramic System Fluorescence Radiation

LaF₃ is an ideal low-phonon host for rare earth ions due to its ability to form extensive solid solutions with all the rare earth ions, but its chemical and mechanical stability limited its application. Oxyfluoride transparent glass ceramics containing rare earth doped LaF₃ nanocrystals, for which the LaF₃ nanocrystals are embedded in the oxide glass that is chemically and mechanically stable, have both advantageous of LaF₃ crystal and oxide glass. Without sacrificing good glass-forming ability, glass stability and ease of glass fabrication, improved luminescence properties for the doped rare earth ions were achieved due to the precipitation of a fluoride crystalline phase with low maximum vibrational energy within an oxide glass matrix of high stability. A number of useful properties for transparent glass ceramics were obtained thereof, especially for photonics applications such as fiber amplifiers, upconversion lasers and displays. Here we present a systematic investigation on the fluorescence spectroscopy properties for Tm³⁺-doped oxyfluoride glass ceramics containing LaF₃ nanocrystals under direct excitation and selective excitation of ¹D₂ level at about 20 K. The thesis is divided into three parts:Part one:A systematic investigation on the optical fluorescence emission for Tm³⁺-doped oxyfluoride glass ceramics containing LaF₃ nanocrystals has been carried out in the spectral range of 400 nm to 900 nm under the direct excitation of ¹D₂ level at low temperature. Specific optical transitions related to the corresponding fluorescence emission bands are studied based on the experimental measurements of fluorescence emission in frequency and time domain. Fluorescent emissions from the ions in crystal phase were observed and their spectroscopic properties were explored. The fluorescent dynamical process shows that the temporal decay of fluorescence emission consists two parts: a fast decay from the ions in glass phase and a slower decay from the ions in crystal phase.Part two:Fluorescence from the Tm³⁺ ions in crystal phase and glass phase were separated under selective exciting the ¹D₂ level of Tm³⁺ ions in transparent oxyfluoride glass ceramics containing LaF₃ nanocrystals, which makes some emission spectra only come from the crystal phase and others only from glass phase. We discussed the effect to optical characteristics of two local field ions from the interaction between glass oxide and fluoride from crystal phase.Part three:Exciting the Tm³⁺-doped oxyfluoride glass ceramics, the influence of phonon on the frequency up-converted fluorescence emission is studied with laser spectroscopy in different symmetry configuration of matrixes and different ambient temperature. The photon energy can be adjusted by varying contents of SiO₂ in Tm³⁺-doped glass and glass ceramics, which will affect the up-converted fluorescence emission. Since the phonon energy depends on the temperature, the variation of the temperature can also affect the population rate of ³H₄ level in Tm³⁺-doped low photon energy LaF₃ material, improving the up-conversion efficiency.