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.