In the present study, oxyfluoride glass-ceramics (GCs) containing NdF3-doped LaF3 nanocrystals were prepared with different amounts of Ag as a co-dopant. The structural and optical properties of the GCs were characterized to identify the presence of the metallic nanoparticles, as well as their role in Nd3+ photoluminescence. Site-selective emission spectra show that Ag co-doped samples, thermally treated in an N2 atmosphere, exhibit increased luminescence of Nd3+ ions in the crystalline phase compared to Ag-free analogues. This effect can be attributed to the local field enhancement at the LaF3 nanocrystals due to the presence of Ag0 nanoparticles.
Tuning color output and enhancing upconversion emission of Er3+ ions in transparent sodium lutetium fluoride glassceramics in bulk and optical fibers, by adjusting the Yb3+ doping level and the excitation power, has been demonstrated. The addition of Yb3+ enhances the UC emission and tunes the color from green to yellow due to an increase of the red-to-green intensity ratio. Moreover, the relative emission intensities of blue, green, and red emissions can be changed by controlling the excitation power which tunes the color from yellow to green.
In this work, we report the influence of the excitation power density on the upconversion emission of Er3+ ions in novel glass-ceramic optical fibers containing NaLuF4 nanocrystals codoped with 0.5ErF3 and 2YbF3 (mol%) prepared by the rod-in-tube method and controlled crystallization. Intense upconverted green and red emissions due to (2H11/2,4S3/2)→4I15/2 and 4F9/2→4I15/2 transitions, respectively, together with a blue emission due to 2H9/2→4I15/2 transition has been observed under excitation at 980 nm. The upconversion emission color changes from yellow to green by increasing the excitation power density which allows to manipulate the color output of the Er3+ emission in the glass ceramic fibers. The tunable emission color is easily detected with the naked eye. This interesting characteristic makes these glass-ceramic fibers promising materials for photonic applications.
Transparent oxyfluoride glass-ceramics obtained by the adequate heat treatment of Nd3+-doped glass with composition 70SiO2–7Al2O3–16K2O–7LaF3 (mol%) are investigated. Site-selective laser spectroscopy demonstrates that depending on the Nd3+ concentration, cubic (α-phase) and hexagonal (β-phase) KLaF4 nanocrystals precipitate from the starting glass. The presence of both crystalline phases are unambiguously identified from the emission and excitation spectra and lifetime measurements of the 4F3/2 state of Nd3+ ions. The spectroscopic results are in agreement with those obtained with XRD and HR-TEM techniques: α-KLaF4 nanocrystals are found to be present for all NdF3 concentrations whereas β-KLaF4 nanocrystals are predominant in the GC samples doped with 0.5 mol%.
Transparent oxyfluoride glass-ceramics obtained by the adequate heat treatment of Nd3+-doped glass with composition SiO2-Al2O3-Na2O-LaF3 are investigated. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM) show that the precipitated nanocrystals are LaF3 with a crystal size between 9-12 nm. Furthermore, energy dispersive X-ray (EDX) analysis shows the incorporation of Nd3+ ions into the LaF3 nanocrystals. Site-selective and time-resolved emission and excitation spectra of the 4F3/2 and 4F5/2 states, allows to unambiguously isolate the emission of Nd3+ ions in LaF3 nanocrystals which shows well defined spectra, similar to those obtained for pure LaF3 crystal.
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