3-Dimensional heat analysis in short-length Er^3+/Yb^3+ co-doped phosphate fiber laser with upconversion

A 3-dimenstional (3D) heat flow model of laser diode (LD) pumped short-length Er(3+)/Yb(3+) heavily co-doped phosphate fiber laser that includes the energy-transfer upconversion (ETU) effects has been developed. The fully 3D analytical solution with the consideration of longitudinal heat flow has been given to describe the temperature distribution in phosphate fiber. The calculated results show that both ETU processes and longitudinal heat conduction have a great influence on the fiber laser performance. Finally, we have validated the analytical expression by measuring the temperature distribution of an end-pumped short-length Er(3+)/Yb(3+) co-doped fiber laser, which was placed into the copper tube.