Highly efficient Yb³⁺-doped channel waveguide laser at 981 nm

Channel waveguide lasers operating at 981 nm are demonstrated in KY_1−x−yGd_xLuy(WO₄)₂:Yb³⁺ waveguides grown by liquid phase epitaxy onto undoped KY(WO₄)₂ substrates and microstructured by Ar⁺ beam etching. Under pumping at 934 nm of samples with different waveguide geometry and outcoupling degree, a record-high slope efficiency of 76% versus absorbed pump power and a record-high output power of 650 mW for rare-earth-ion-doped microstructured channel waveguide lasers is achieved. The laser performance is compared to that of the same devices when pumping at 981 nm and lasing near 1025 nm.