Effect of erbium concentration on optical properties of Er:YLF laser crystals

Four Er-doped LiYF4 crystals with different Er-concentrations were grown by Czochralski method. The laser crystals were characterized by measurements of ICP-AES, XRD, absorption spectra, up-conversion fluorescence spectra, near-infrared (NIR) and mid-infrared (Mid-IR) fluorescence spectra, as well as luminescence decays. It was found that the heavily 15 at% Er-doped YLF crystal is more proper in up-conversion or ∼3 μm laser applications; while the 5 at% Er-doped YLF is a better candidate for ∼1.5 μm lasers within these four crystals.