Concentration-dependent optimization of Yb3+/Er3+ highly-doped phosphate glass waveguide amplifiers and lasers using a microscopic statistical formalism

Abstract The dependence of the optimal performance of bidirectionally-pumped integrated amplifiers and lasers based on fs-laser written Yb 3+ /Er 3+ -codoped phosphate glass waveguides on the concentration of dopants is numerically analysed. A novel macroscopic rate-equation propagation model is used which considers concentration-dependent rates for the energy-transfer inter-atomic migration-assisted mechanisms. Optimal small-signal gain for an amplifier and output laser power for a ring laser are computed for various working conditions and broad dopants-concentration ranges. Optimal waveguide lengths are also analysed in detail. The large variations obtained in the dopants concentration required for optimal amplifier gain or output laser power and in the waveguide optimal length confirm that a previous rigorous numerical design is essential in order to achieve the optimized performance of these active devices.