Diamond-saw-diced multi-color ridge Pr,Gd:LiYF₄ waveguide lasers

Single-crystalline layers of 0.3 at.% Pr, 3.5 at.% Gd:LiYF₄ were grown by liquid phase epitaxy and microstructured using precision diamond-saw dicing, resulting in low-loss (0.16 dB/cm in the red) ridge waveguides with a sub-nm sidewall surface roughness. The continuous-wave red channel waveguide laser generated 504 mW at 639.6 nm with a high slope efficiency of 57.8%, a laser threshold of 34 mW, linearly polarized emission (σ), and high beam quality (M² = 1.66). Laser operation in the orange and deep-red was obtained. The polarized emission properties of Pr³⁺ ions in the epitaxial layers are reported.