Phase measurement in long chirped pulses with spectral phase jumps.

Characterization of the chirp in stretched laser pulses is performed with a novel, simple method, based on the use of a plasma mirror switch coupled with a spectrometer. For a 36nm full width half maximum bandwidth and 360ps chirped laser pulse, the spectral phase of the pulse was measured in few hundred of points. Besides the chirp measurement, the approach allows the detection of jumps in the optical path, hence spectral phase jumps corresponding to less than 3ps.