Observation of Midinfrared 4- Emission in Ho3+-Doped Fluoroaluminate Glasses

Ho³⁺ activated fluoroaluminate glasses were prepared successfully via melt-quenching method. Not only 2- and 2.85-μm emissions but also 4-μm emissions were observed for the first time by 900-nm Ti: sapphire laser pumping. The optimal midinfrared emissions were obtained when Ho³⁺ concentration reaches 1 mol%. Spectroscopic properties and energy transfer mechanism of Ho³⁺ were investigated in detail. Results indicate that the prepared glasses possess high midinfrared transmittance (90%), large emission cross sections at 2 μm (7.6 × 10^-21 cm²), 2.85 μm (17.6 × 10^-21 cm²), and 4 μm (6.87 × 10^-21 cm²) together with superior gain properties. It is suggested that Ho³⁺ activated fluoroaluminate glass is an attractive candidate for midinfrared laser materials application.