A novel measurement scheme for the radial group delay of large-aperture ultra-short laser pulses

•This measurement scheme is based on self-reference, which can work without any extra struggle for the wanted reference pulses.•The size of optical components in this RGD measurement scheme can be decreased when compared with the other methods.•It is the first time to realize the direct RGD measurement of large-aperture ultra-short laser pulses.

In femtosecond high-peak-power laser system, the radial group delay (RGD) of the pulse front introduced by conventional lens-based beam expanders can significantly decrease the achievable focal intensity, especially when it is larger than the pulse duration. In order to quantitatively analyze and compensate the RGD, a novel measurement scheme based on self-reference and second-order cross-correlation technology is proposed and applied to measure the RGD of the large-aperture ultra-short laser pulses directly. The measured result of the RGD in a 200 TW Ti:sapphire laser system is in good agreement with the theoretical calculation. To our knowledge, it is the first time to realize the direct RGD measurement of large-aperture ultra-short laser pulses.