Properties of steady state in Er^(3+) Yb^(3+) co doped phosphate glass for optic

Transitions of laser diode (LD) pumped Er^(3+)-Yb^(3+) co-doped glass laser are rather complicated. Considering energy transfer between Er^(3+) and Yb^(3+) ions, cross-relaxation, upconversion luminescence, and other transition processes, rate equations of quasi-three energy-level-system of the Er^(