Enhanced green upconversion in Tb3+–Yb3+ co-doped oxyfluoride glass ceramics containing LaF3 nanocrystals

Tb3+–Yb3+ co-doped transparent oxyfluoride glass ceramics containing LaF3 nanocrystals were successfully fabricated by the melt-quenching technique in air atmosphere. The structural and luminescent properties were systemically investigated by X-ray diffraction, transmission electron microscopy and upconversion spectra. All samples exhibited intense characteristic emissions of Tb3+ (5D4→7FJ (J=3−6) and 5D3→7FJ (J=4−6)) under 980 nm laser excitation. Besides, the upconversion intensity in glass ceramics was stronger than that in precursor glass and increased with crystallinity degree, which could be ascribed to the incorporation of Tb3+ and Yb3+ ions into LaF3 nanocrystals with low phonon energy. Laser power dependence of upconversion proved two-photon process was responsible for green emission.