Spectral broadening and pulse duration reduction during cross-polarized wave generation:: influence of the quadratic spectral phase

Cross-polarized wave (XPW) generation is used for the contrast improvement of ultra-intense femtosecond laser pulses in a double CPA configuration. We present theoretical and experimental evidence that the XPW output spectrum depends in a predictable way on the input chirp. Therefore, a chirp controlled pulse can experience a pulse duration shortening up to a factor of root 3, and an initial amount of chirp that leads to the exact preservation of the spectral width of a given pulse can be predicted.