Microspheres of diameters ranging from 30 μm to 100 μm, obtained from 0.1Pr3+-0.5Yb3+ codoped phosphate glass were fabricated and calibrated as optical temperature sensor. When the
microspheres where pumped under 457 nm laser excitation, Pr3+ typical emission was observed as
well as emission due to a Down Conversion (DC) process from Pr3+ to Yb3+ ions. Furthermore,
whispering gallery modes (WGM) peaks superimposed to the Pr3+ and DC emission bands were
observed. The microsphere was calibrated as a function of temperature using the intensity ratio of
the 925 and 875 nm Pr3+ bands and the spectral red-shift from the WGM. Temperature uncertainty
was obtained from both techniques obtaining values of 0.7 K and 0.4 K for the band ratio and
WGM results, respectively.
