Enhanced 2.0 μm emission in oxyfluoride glass-ceramics containing nanocrystals MF2 (MF3): Ho3+,Tm3+ (M = Ca, Ba, and La)

Transparent glass-ceramics containing MF2(MF3):Ho3+,Tm3+ (M = Ca, Ba, and La) nanocrystals have been prepared by melt quenching and subsequent thermal treatment. X-ray diffraction and transmission electron microscopy analysis confirmed the precipitation of MF2 (MF3) nanocrystals among the glass matrix. Energy-dispersive X-ray spectroscopy results evidenced the incorporation of Tm3+ and Ho3+ into the MF2 nanocrystals. Intense 2.0 μm emission originating from the Ho3+: 5I7 → 5I8 transition was achieved upon excitation with 808 nm laser diode. A large ratio of the forward Tm3+ → Ho3+ energy transfer constant to that of the backward process indicated high efficient energy transfer from Tm3+ (3F4) to Ho3+ (5I7), and benefited from the reduced ionic distances of Tm3+-Tm3+ and Tm3+-Ho3+ pairs and low phonon energy environment with the incorporation of rare earth ions into the precipitated MF2 nanocrystals. The results indicate that oxyfluoride glass-ceramic is a promising candidate for 2.0 μm laser.