Kinetic limitation of anti-Stokes luminescence of Er and Yb doped infrared upconversion materials

Infrared-to-visible wave-length conversion in the Yb-Er doped phosphors system has been described by a simple three level model based on two ions mechanism. The excitation in the range of 900-1000 nm of an IR-photon is first absorbed by Yb ion as a sensitizer attributed to the resonant energy transition in Er ion from S→I and F→I, respectively for green and red emission. The essential energy transfer processes in this system i.e. upconversion from I and I, cross-relaxation from S and F are taken into account. The limitations of the rate-equation approach are examined with a focus on the underlying dynamics of this rare-earth system.