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 fluorescence emission in Yb³⁺-sensitized Er³⁺-doped germanosilicate optical fibers excited with cw radiation at 1.064 μm is investigated. The experimental results revealed an eightfold enhancement in the visible upconversion emission intensity as the fiber temperature was increased from 17 °C to 180 °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 occupation number, has proven to agree very well with the experimental data Received: 6 April 1999 / Revised version: 27 August 1999 / Published online: 27 January 2000