Solution synthesis and spectroscopic characterization of high Er3+ content LaF3 for broadband 1.5 μm amplification

Erbium-doped LaF3 transparent gels have been synthesized by the solution synthesis of metal inorganic precursors. The solid solubility of Er3+ can reach 60 mol %, which is almost double the solubility limit of Er3+ in LaF3 synthesized by the Bridgman technique. A quantitative analysis of the absorption and emission spectral data shows that the quantum efficiency of the 1.55 μm emission band is comparable to that of melt grown single crystal. However, the emission spectral width of the 1.55 μm band is found to be 40% greater than that of the melt grown single crystal, which extends the spectral bandwidth to 11 THz. The high solid solubility of Er3+ supports 36 cm−1 single pass optical gain, which is three times higher than that in zirconium barium lanthanum aluminum sodium glass. The high Er3+ concentration and spectral bandwidth enable LaF3:Er amplifiers to be made by a low-temperature solution-based technique.