Pulse-front control of 15-TW pulses with a tilted compressor, and application to the subpicosecond traveling-wave pumping of a soft-x-ray laser

We have implemented an adjustable traveling-wave method of excitation for the transverse pumping of laser media based on tilting one of the gratings of the compressor of a chirped pulse amplification [Opt. Commun.56, 219 (1985)] (CPA) laser chain. We show that the only requirement to obtain the best locally compressed pulse is to slightly tilt and translate one of the gratings from its original position. Exact and approximate expressions of these two motions are derived, allowing an easy reconfiguration of any CPA laser. An experimental validation is performed with the first observation of a unidirectional soft-x-ray lasing when subpicosecond pumping pulses are used.