Improving the brightness of a multi-kilowatt single thin-disk laser by an aspherical phase front correction

We report on results obtained with an aspherical mirror to compensate for the phase front aberrations of a cw thindisk laser with a single disk in the resonator. A record output power of 5kW with a beam quality suitable for laser cutting (beam propagation factor M2 ¼ 9:2) has been achieved.