Mirrorless Yb3+-Doped Monoclinic Double Tungstate Waveguide Laser Combining Liquid Phase Epitaxy and Multiplexed Beam fs Laser Writing

In this paper, a mirrorless Yb³⁺-doped KY_1-x-yGd_xLu_y(WO₄)₂ waveguide laser with cw operation at 981.5 and 1001 nm, fabricated by liquid phase epitaxy and femtosecond laser microstructuring, is reported. A planar waveguide was fabricated by growing an Yb³⁺-doped KY_1-x-yGd_xLu_y(WO₄)₂ epitaxial layer by liquid phase epitaxy over a KY(WO₄)₂ substrate. This planar waveguide was then microstructured by means of a multiplexed beam femtosecond laser writing technique in order to define ridge waveguides. Mirrorless laser action is demonstrated in ridge waveguides with different fabrication parameters, obtaining maximum slope efficiency of 78% versus absorbed power, which confirms the feasibility of this technique for the development of integrated laser devices.