Fluorescence thermometry application of photoluminescence image from Cr-doped YAG

The temperature dependence of a photoluminescence (PL) image from a Cr-doped Y3Al5O12 (YAG:Cr) crystal was evaluated for a fluorescence thermometry application. The brightness of a red PL image of YAG:Cr was found to be increased by increasing the temperature. Temperature variations of the peak intensity and peak area of red PL related to the PL peaks at lambda = 680, 690, 708, and 725 nm were evaluated to reveal the cause of the increase in brightness of the PL image. While intensities of the PL peaks at lambda = 690, 690, and 708 nm decreased with temperature due to thermal quenching, the peak intensity at lambda = 725 nm and the peak area increased with temperature up to 250 & DEG;C. The latter factor greatly affects the temperature variation of the brightness of PL images. The increase in the brightness of the PL image with temperature is evidently linked with the thermal excitation of electrons at the E-2 level responsible for the increase in the PL peak area. Cr concentration suitable for the temperature sensor is suggested based on the temperature variation of the PL peak area.