Preparation Of Tm³⁺/Yb³⁺ Co-doped Oxyfluorosilicate Glass-ceramic Waveguide And Research On The Optical Property

Rare earth (RE) doped transparent oxyfluoride glass ceramics, which have been extensively studied, have good potential application value in laser, display and optical communication. This is not only because of their high mechanical strength and excellent chemical stability like oxide glass, but also their low phonon energy and efficient luminescence properties like fluoride glass. In this paper, the Tm3+/Yb3+co-doped Na2O-La2F6-Al2O3-SiO2 transparent glass ceramics were fabricated by high temperature sintering method, and the fluorescence and waveguide characteristic were mainly studied.Firstly, the influence of different heat treatment on micro structure and luminescence property of RE doped glass ceramics were measured by x-ray diffraction analysis, transmission electron microscope analysis, absorption and luminescence spectra analysis. It was shown that there were some LaF3 nano-crystals generated and evenly dispersed in the glass matrix. As the heat treatment temperature increasing (650,670,700℃), the size of LaF3 nano-crystals gradually increased (14.2,20.7,24.4 nm), while the quality of transparency declined (86,84,79%) in the corresponding. The sample became opaque when the temperature increased to 750℃. The up-conversion emission at 475 nm,650 nm and 796 nm, which are correspond to1G4â†'3H6,1G4â†'3F4 and 3H4â†'3H6 transition of thulium, were observed obviously excited by 980 nm laser. The reason for the bright blue fluorescence was that Tm3+/Yb3+ions were chiefly incorporated into LaF3 nano-crystals which provide a low-phonon-energy environment (350 cm-1) to reduce the multiphonon relaxation and realize the fluorescence emission. The mechanism discussion of up-conversion demonstrated that the blue fluorescence (475 nm) vest in three-phonon absorption and the red fluorescence (650 and 796 nm) vest in two-phonon absorption. The 1.47μm infrared luminescence, which is correspond to 3H4â†'3F4 transition of thulium, had also been observed and the full width at half maximum was about 100 nm under the excitation of 980 nm laser. The fluorescence intensity of 1.47μm was much weaker than that of up-conversion fluorescence. That was due to the competition between 1.47μm and 796 nm emission, the fluorescence emission probability was 0.083 to 0.893.Secondly, the glass and glass ceramic planar waveguides were prepared by ion-exchange method. The m-line, refractive index profile and effective diffusion depth properties of the both planar waveguides were measured contrastively by prism coupler. Both glass and glass ceramic matrixes were immerged in a molten salt mixture with 99.5 KNO3 and 0.5 AgNO3 in mole at 340℃for 3min,3.5min,4min and 4.5min to form waveguides. The prism coupler test results indicated that both matrixes were good at ion-exchange. The refractive index change and diffusion coefficient were 0.0116+0.00095 and 0.054μm2/s for glass planar waveguide, respectively, while that were 0.0121+0.000925 and 0.071μm2/s for glass ceramics waveguide.This study shows that RE doped transparent oxyfluosilicate glass ceramics have excellent performance in up-conversion fluorescence and ion-exchange. It can be concluded that this kind of materials have a good potential value in up-conversion laser and optical communication.