Er:LiYF4 planar waveguide laser at 2.8 <i>μ</i>m

We report on a mid-infrared erbium planar waveguide laser operating on the 4I11/2 → 4I13/2 transition. It employs a heavily doped 10.6 at. % Er3+:LiYF4 single-crystalline layer grown by liquid-phase epitaxy. The waveguide laser delivers a maximum output power of 191 mW at ∼2809 nm with a slope efficiency of 15%, a linear polarization, and a laser threshold of 134 mW. The waveguide propagation losses are 0.4 ± 0.2 dB/cm. The polarized spectroscopic properties of the Er3+:LiYF4 layers are also investigated. The stimulated-emission cross section of Er3+ ions amounts to 0.87 × 10−20 cm2 at 2809 nm for π-polarization. Er3+:LiYF4 epitaxial layers represent a promising platform for integrated low-loss mid-infrared light sources.