Optical Temperature Sensor Based on Green Fluorescence of Er2O3 $\cdot $ 3Nb2O5 Phosphor

We report an optical temperature sensor based on the thermal effect of fluorescence intensity ratio of 980-nm upconverted green 530- and 550-nm emissions of Er
₂
O
₃
· 3Nb
₂
O
₅
phosphor. The sensor consists of only a 980-nm LD, two narrow-band interference filters and two Si-photocells, while being without the use of optical lens to collect the fluorescence. Thermal effect on the photocell output was calibrated. The results show that the output has a linear relation to the temperature and the linearity is independent of input power. The performance characterization shows that the sensor exhibits a relative sensitivity (5-7) 10
^-3
K
^-1
in the temperature range of 303-353 K. The setup is applicable to other Er
³⁺
-doped materials with a higher relative sensitivity.