Temperature dependence of the whispering gallery modes obtained in a glass microsphere codoped with Er3+-Yb3+ ions

A microsphere made from a Strontium Barium Niobate glass codoped with Er3+ and Yb3+ ions is proposed in order to be employed as an optical temperature sensor. By means of the fluorescence intensity ratio technique, the effect of temperature changes in the emission bands of the erbium thermalized levels is characterized. At the same time, the position in wavelength of the whispering gallery modes is altered as a consequence of temperature shifts. The analysis of temperature shifts enables to estimate that the temperature could be obtained with a resolution limit of about 0.01 K.