The composition of holmium-doped fibers has a fundamental influence on their fluorescence and laser properties. The same can apply for the preparation method, since it may affect the glass matrix in the close vicinity of active ions. We present fibers with different dopant levels, namely Al 2 O 3 and Ho 3+ , prepared through several methods to find their relations to fiber characteristics. We investigated fluorescence lifetime, laser threshold and laser slope efficiency as a function of Al/Ho molar ratio and Al 2 O 3 content. It was proved laser slope efficiency is affected primarily by Al/Ho ratio; for high-efficiency fibers with low laser threshold the Al/Ho needs to be greater than 50. Fluorescence lifetime was found to depend on both Al/Ho ratio and on total Al 2 O 3 content. It was increasing with Al/Ho ratio as well as with total Al 2 O 3 concentration. The best-performing fibers showed slope efficiency above 70%, laser threshold below 200 mW and fluorescence lifetime longer than 1200 μs. • Co-doped nanoparticles were used for preparation of holmium-doped fiber lasers • Powder-based sintering approach was used for preparation of holmium-doped fiber lasers • Fluorescence lifetime depends on Al/Ho molar ratio as well as on Al 2 O 3 content • Slope efficiency depends primarily on Al/Ho molar ratio not on Al 2 O 3 content • The best slope efficiencies are obtained in fibers with Al/Ho molar ratio above 50
Kamrádek et al. (Sun,) studied this question.