Characteristics of chromium doped spinel crystals for a fiber-optic thermometer application

The chromium doped spinel crystals, MgAl2O4:Cr3+, have been grown using floating zone technique and its application for the fiber-optic thermometer is discussed on the basis of the temperature dependence of the fluorescence lifetime. Lifetimes of the spinel crystals (tau=10 ms), which decrease with temperature, were about 3 times larger than that of the ruby crystals (tau=4 ms) at room temperature. Temperature coefficients of the photoluminescence (PL) lifetimes for spinel crystals (37 mus/K) are also 3 times longer than that for the ruby crystals (10 mus/K). The spinel crystals are potentially useful sensor probes for the fiber-optic thermometer, which have an advantage of high sensitivity due to long PL lifetime and large temperature coefficient. (C) 2002 American Institute of Physics.