Highly efficient <i>Q</i>-switched Yb:YAG channel waveguide laser with 5.6 W of average output power

In this Letter, we present high-power continuous wave (CW) and <i>Q</i>-switched femtosecond laser-written Yb:YAG channel waveguide lasers. In <i>Q</i>-switched operation, obtained by a semiconductor saturable absorber mirror (SESAM), as well as in CW operation, the laser generates average output powers of more than 5.6 W and reaches slope efficiencies above 74%. The <i>Q</i>-switched laser operated at a maximum repetition rate of 5.4 MHz with a minimum pulse duration of 11 ns, and with a maximum pulse energy of 1 μJ. This laser has almost an order of magnitude higher average output power than previously reported <i>Q</i>-switched channel waveguide lasers.