Bulk lateral shearing interferometry for spatiotemporal study of time-varying ultrashort optical vortices

The spatiotemporal measurement of ultrashort laser beams usually involves techniques with complex set-ups or limited by instabilities that are unable to accurately retrieve the frequency-resolved wavefront. Here, we solve these drawbacks by implementing a simple, compact, and ultra-stable spatiotemporal characterization technique based on bulk lateral shearing spectral interferometry using a birefringent uniaxial crystal. We apply it to retrieve complex spatiotemporal structures by characterizing ultrafast optical vortices with constant and time-varying orbital angular momentum. This technique can operate in all the transparency range of the anisotropic elements,enabling the characterization in different spectral ranges like infrared, visible, or ultraviolet.