Low-threshold, mirrorless emission at 981nm in an Yb,Gd,Lu:KYW inverted rib waveguide laser

In this work, we demonstrate 3-level laser operation in a Yb,Gd,Lu:KYW waveguide laser fabricated by combination of liquid phase epitaxy and Ar+ ion beam milling. Laser emission was observed at 981 nm with an absorbed threshold power of 23 mW and a slope efficiency of 58% without the use of any mirrors. With an HR/6%T cavity, the threshold was reduced to 13 mW. The output was single mode with beam radii of 4.8 µm and 3 µm in the in-plane and out-of-plane direction respectively. Laser emission was also observed at 999.8 nm with a threshold of 8 mW by using mirrors favouring the 999.8 nm transition and forming an HR/5%T cavity.