Deep-red planar waveguide laser operation of Eu:KY(WO) layers.

We report on the first deep-red europium planar waveguide laser. It employs 30-µm thick heavily-doped 11.5 at.% Eu:KY(WO) layers grown by liquid phase epitaxy on undoped substrates using KWO as a solvent. When pumped with a green laser at 532 nm, the Eu-waveguide laser delivers a maximum output power of 7 mW at 704.7 nm with a slope efficiency of 9.5%, a laser threshold of 21 mW, and linear polarization. The waveguide propagation losses are as low as 0.05 dB/cm. The morphology, vibronic, and spectroscopic properties of the epitaxial layers are also studied. In the deep red, for the D → F transition, the stimulated-emission cross-section reaches 1.76 × 10 cm at 704.7 nm for light polarization || , and the luminescence lifetime of the D manifold is 472 µs.