Optical properties of europium-activated hafnium fluoride-based glasses

摘要

We have studied the optical absorption, luminescence, and electron paramagnetic resonance of EuF3- and EuF2-activated fluorohafnate glasses. The glasses prepared with EuF2 contain both di- and trivalent europium. The fraction of divalent europium clusters in the glass host decreases with decreasing EuF2 concentration. Eu2+ luminescence in the fluorohafnate glasses is quenched, which is due the overlap of Eu2+ excited state levels with the conduction band of the glass, resulting in nonradiative relaxation through Hf3+ levels in the conduction band. The Eu3+ luminescence spectra contain lines corresponding to transitions from several levels of the (5) D multiplet to levels of the (7) F multiplet. The relationship between transitions from different (5) D levels depends on europium concentration and temperature.