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

Thermometer probe using the chromium doped spinel crystals, MgAl/sub 2/O/sub 4/:Cr/sup 3+/, has been fabricated and the wavelength dependences of PL lifetime are evaluated as compared with those using ruby crystals. Lifetimes and temperature coefficients of the spinel crystals (/spl tau/=10 ms, 37 /spl mu/s/K), which were typically 3 times larger than that of the ruby crystals (/spl tau/=4 ms, 10 /spl mu/s/K), varied from 4.74 ms to 1.65 ms with wavelength from 667.5 nm to 780 nm.