Fully coherent plasma x-ray laser by injection of a parametrically amplified high-order harmonic beam*

Conventional plasma x-ray lasers have the characteristics of spatial coherence, while less temporal one. In order to realize fully coherent plasma x-ray lasers, we have employed a seed-amplifier scheme. In this setup, a high-order harmonics as a seeder is injected into an amplifier plasma medium. As a result, the harmonics is amplified while maintaining its original coherencies. For generation of a narrow beam divergence and intense high-order harmonics, we focus on the x-ray parametric amplification. The high-order harmonics generated in two He gas jets are amplified due to parametric interaction, by which the quality of the harmonics are even improved. On the other hand, plasma amplifier is created by using the same Ti:Sa laser by a grazing incident pumping. To meet the requirements on the spatial and spectral coupling is essential to achieve the efficient amplification. Thus, the central wavelength of the laser is tuned at 792.3 nm, by which the lasing transition (13.9 nm) matches the 57^th order harmonics. The preliminary results of the parametric amplification of the harmonics will be presented.