Spectroscopic investigation of 2.02 μm emission in Ho~(3+)/Tm~(3+) codoped transparent glass ceramic containing CaF_2 nanocrystals

摘要

Tm~(3+) and Ho~(3+) codoped transparent glass ceramic (GC) containing CaF_2 nanocrystals were fabricated by melt-quenching and subsequent thermal treatment. X-ray diffraction and transmission electron microscopy analysis confirmed the precipitation of CaF_2 nanocrystals among the glass matrix. Energy-dispersive x-ray spectroscopy results evidenced the incorporation of Tm~(3+) and Ho~(3+) into the CaF_2 nanocrystals. Judd-Ofelt parameters were calculated based on the absorption spectra, the smaller Ω _2 and larger Ω _6 imply that Tm~(3+) and Ho~(3+) ions has entered into a symmetrical ionic crystal field. 2.02 μm emission spectral of the GC samples were recorded at room temperature with an excitation of 808 nm laser diode. The enhancement of the emission at 2.02 μm in the GC samples could be attributed to more efficient cross relaxation process of Tm~(3+):~3H_4+Tm~(3+):~3H_6 → 2Tm~(3+):~ 3H_4, and energy transfer from Tm~(3+) to Ho~(3+) benefited from the incorporation of rare earth ions into CaF_2 nanocrystals.