240-fs pulses with 22-W average power from a passively mode-locked thin-disk Yb:KY(WO/sub 4/)/sub 2/ laser

Summary form only given. Femtosecond lasers with high average output power are of great interest for numerous applications such as simple and efficient nonlinear frequency conversion or multi-photon spectroscopy. Such lasers can be realized by combining a diode-pumped thin-disk laser head with a semiconductor saturable absorber mirror (SESAM) for passive mode locking. In this paper we present the first passively mode-locked thin-disk laser which is based on the novel gain medium Yb:KY(WO/sub 4/)/sub 2/ (Yb:KYW). This laser crystal has a larger amplification bandwidth than Yb:YAG and is therefore suitable for significantly shorter pulses. We obtained 240-fs pulses at 1028 nm with 22-W average power and 3.3-MW peak power. The pulse repetition rate is 24.6 MHz, and the pulse energy is 0.9 /spl mu/J. The beam quality is close to the diffraction limit, with M/sup 2/ = 1.1. Focusing the beam to a spot diameter of 2 /spl mu/m would result in a peak intensity of 2 /spl middot/ 10/sup 14/ Wcm/sup -2/.