Fiber length impact on MIR cascade lasing in yellow Dy-doped ZBLAN fiber lasers

Recent advances in low-loss fluoride glasses have enabled the development of Dy-doped ZBLAN fibers for yellow lasers, either tunable or not, pumped by blue GaN laser diodes. Recently, the impact of excited state absorption on Dy-doped tunable FLs has been investigated, showing potential enhancements enabled by MIR cascade lasing. In this study, the optimal fiber length for MIR and yellow emission was analyzed as a function of pump power and mirror reflectivity. Results reveal a mismatch between the optimal lengths for yellow and MIR emission. This suggests the possibility of minimizing the cascade lasing threshold through cavity optimizations aimed at reducing the length mismatch, thus enhancing performance at low pump power levels too.