Model of Longitudinally Laser Diode Pumped Erbium–Ytterbium-Codoped Phosphate Glass Microchip Laser With Upconversion

A theoretical model of longitudinally laser diode (LD) pumped erbirum-ytterbium-codoped phosphate glass microchip laser that includes the influence of cooperative upconversion and cumulative upconversion effects has been developed. The analytic solution with an approximation of top-hat pump and laser profile is derived to show the influence of the both upconversions on the threshold and slope efficiency. When the Guassian profiles of both pump and oscillating lasers are considered, rigorous numerical calculations have been made to study the influence of cooperative upconversion and cumulative upconversion effects. The results of calculations are in good agreement with our experimental data. The influence of the round-trip dissipative optical loss, the waist of pump beam and the transmission on laser optimization is also discussed when considering the upconversion effects.