The spectrally resolved photoluminescence decay in YAG:Er, ZnO and SiO2 crystals

We present an optical setup for measuring spectrally resolved photoluminescence (PL) mean decay time using conventional UV LED with sinusoidal excitation and a phase shift method. The phase sensitive detection was applied on the Er-doped yttrium aluminium garnet single crystal (YAG:Er, grown by the micro-pulling-down method) and hydrothermally grown zinc oxide micro-crystallites (ZnO). Commercial ZnO and silicon oxide (SiO2) microcrystalline powders were measured for comparison. SiO2 powder was annealed in O2 plasma at 500 °C for cleaning. While YAG:Er shows well resolved greenish PL peaks with mean decay time about 15 μs related to the Stark splitting of Er3+ (4f11) states and ZnO micro-powder broad reddish PL with similar PL decay time, the plasma treated SiO2 powder shows weak bluish defect-related PL with significantly faster mean decay times below 100 ns.