Temperature rise monitoring through red-to-green up conversion in Er3+: Sr0.3Cd0.7F2 crystals

We have determined the temperature into the bulk of a transparent material excited by a red dye tunable laser thanks to a nondestructive method using the green fluorescence emitted by the Er3+ ions incorporated in the material. A homemade Er3+-doped fluorite type mixed crystal was investigated. The green emission obtained following the optical excitation of Er3+ ions around 652 nm is, in this material, much more intense than in the oxides. The green emitting levels are composed of Stark sub-levels whose the electronic populations obey the Boltzmann's law we applied to determine the temperature as a function of time and of the incident power. The percentage of the energy absorbed by the Er3+ ions which is converted into heat was estimated from a thermal model which we developed.