Fiber thermometer based on the cross detection of the fluorescence lifetime of Cr~(3+):YAG crystal fiber and Plank's blackbody radiation from cryogenic up to 1400 ℃

摘要

A fiber thermometer using the cross detection of the fluorescence lifetime and blackbody radiation was presented to measure temperature from -10℃ up to 1400℃. Using a long pure YAG crystal fiber as the seed and a 0.1 at. % Cr_2O_3-doped Y_3Al_5O_12) sintered powder rod as the source rod, a YAG fiber thermal probe with Cr~(3+) -ions doped end was grown by laser heated pedestal growth method. A blackbody cavity was constructed by sintered a thin ceramic layer around the Cr~(3+): YAG fiber end. A phase-locked detection scheme was used for the fluorescence lifetime detection. The fluorescence characteristics of the Cr~(3+) -ions doped YAG was analyzed in a temperature range from -10℃ up to 500 ℃. From 350 ℃ to 1400 ℃ the blackbody radiation signal in a narrow waveband were detected. Because the fluorescence lifetime was intensity independent, it should have the long-term stability and would not change if the fiber connectors of the probes were realigned. So the fluorescence lifetime based temperature measurement could be used to recalibrate that based on the blackbody radiation detection. Preliminary experimental results showed that the system could achieve a resolution much better than 1℃ over the whole temperature range from -10℃ to 1400℃.