Orange Surface Waveguide Laser in Pr:LiYF4 Produced by a Femtosecond Laser Writing.

Depressed-cladding surface channel waveguides were inscribed in a 0.5 at.% Pr:LiYF4 crystal by femtosecond Direct Laser Writing. The waveguides consisted of a half -ring cladding (inner diameter: 17 mu m) and side structures ("ears") improving the mode confinement. The waveguide propagation loss was as low as 0.14 +/- 0.05 dB/cm. The orange waveguide laser operating in the fundamental mode deliv-ered 274 mW at 604.3 nm with 28.4% slope efficiency, a laser threshold of only 29 mW and linear polarization (pi), repre-senting record-high performance for orange Pr waveguide lasers. (c) 2023 Optica Publishing Group