Optimized ancillae generation for ultra-broadband two-dimensional spectral-shearing interferometry

To overcome the challenges of ancillae preparation in two-dimensional spectrally sheared interferometry, we apply the approach based on spectral filtering in the Fourier plane of a 4-f zero-dispersion compressor, which allows the generation of two sheared and synchronized monochromatic fields. The scheme provides direct and precise measurement of their spectral shear, greatly improving the accuracy and reliability of spectral phase retrieval. By characterizing few-optical-cycle pulses spanning nearly two octaves of bandwidth, we prove the applicability of this method to sub-single-cycle pulses.