Thermal effect on multiphonon-assisted anti-Stokes excited upconversion fluorescence emission in Yb3+-sensitized Er3+-doped optical fiber

The temperature effect upon infrared-to-visible frequency upconversion fluo rescence emission in Yb3+-sensitized Er3+-doped germanosilicate optical fib ers excited with cw radiation at 1.064 mu m is investigated. The experiment al results revealed an eightfold enhancement in the visible upconversion em ission intensity as the fiber temperature was increased from 17 degrees C t o 180 degrees C. The fluorescence emission enhancement is attributed to the temperature-dependent multiphonon-assisted anti-Stokes excitation process of the ytterbium sensitizer. A theoretical approach that takes into account a sensitizer absorption cross-section, which depends on the phonon occupat ion number, has proven to agree very well with the experimental data.