Recent progress in secondary sources produced by multi-terawatt femtosecond lasers

Summary form only given. X-rays produced from intense subpicosecond laser systems have the unique properties to provide subpicosecond X-ray pulse duration and to be fully synchronized with the laser system. This allows the probing by X-rays of ultrafast phenomena, previously limited to all-visible pump-probe investigation. Ultrafast X-ray science is important to biologists, chemists and physicists because it will allow them to follow atomic motions, which ultimately drive processes like (bio-) chemical reactions and phase transitions, on the time-scale at which they occur. The last 2 years have shown important advances, both in the study of coherent radiation in the sub-keV range by high harmonics or X-ray lasers, and in the development of optical pump-keV X-ray probe ultrafast spectroscopy using synchrotrons and laser-produced plasmas.