Highly efficient Q-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 ? Q-switched femtosecond laser-written Yb:YAG channel waveguide lasers.In ? Q-switched operation, obtained by a semiconductor saturable absorbermirror (SESAM), as well as in CW operation, the laser generatesaverage output powers of more than 5.6 W and reaches slopeefficiencies above 74%. The ? Q-switched laser operated at a maximum repetition rate of 5.4 MHzwith a minimum pulse duration of 11 ns, and with a maximum pulseenergy of 1 μJ. This laser has almost an order of magnitudehigher average output power than previously reported ? Q-switched channel waveguide lasers.