Generation of ultrashort coherent XUV pulses by harmonic conversion of intense laser pulses in gases:: towards attosecond pulses

The generation of high-order harmonics of intense laser pulses focused in gases is an intriguing and spectacular process: nonlinear orders as high as 300 have been reported recently. In addition to its fundamental interest, this radiation presents unique properties of coherence and ultrashort pulse duration that makes it a useful XUV source. The measurement of such short durations has required us to develop new characterization techniques in the XUV range, that have evidenced harmonic pulses as short as a few femtoseconds. This property opens the way to studying ultrafast dynamics in atomic and molecular spectroscopy, solid-state and plasma physics. Moreover, the possibility of generating yet shorter pulses, so-called attosecond pulses, is under investigation.