Excited-State Absorption in ZBLAN:Er3+: Implications for a Diode-Pumped 3-µm Fiber Laser

Erbium-doped fluorozirconate (ZBLAN) fibers are promising candidates for the construction of compact and efficient all-solid-state 3-µm laser sources for surgical applications. Excited-state absorption (ESA) was found to have a major influence on the lasing properties of the erbium 3-µm transition in ZBLAN fibers. An approach has been suggested recently [1], which aims to avoid pump ESA and requires only low pump intensity, thus enabling high-power double-clad diode pumping of the erbium 3-µm fiber laser. However, the values of the relevant ESA cross-sections could not be determined experimentally so far. because the pump excitation is distributed between two metastable levels of erbium in ZBLAN, and ESA transitions from these two levels overlap in the spectral region of interest.