Pulse front distortion occurring in lenses can broaden the temporal profile of the pulse at focus and therefore decrease the focused intensity, especially for large-aperture femtosecond lasers. A previously proposed self-reference cross correlator was improved to directly measure the pulse front distortion of high-peak-power femtosecond lasers. The measured results of a 200 TW/27 fs laser are in good accordance with the calculated value. Moreover, the temporal intensity distribution of the pulse in the focal region was also investigated, in order to better guide and further promote the strong laser-matter interaction investigations. According to the measured PFD, the effective pulse duration at far field of this 200 TW laser was theoretically simulated to be ≈49 fs, which is almost two times the generally regarded 27 fs. As a result, the actually available focused intensity of this laser is only 55% of the case without pulse front distortion.
Tunable, high peak power terahertz radiation from optical rectification of a short modulated laser pulse