Fig. 1: Experimental configuration for beam shaping and measurement.

An input beam (in our case, a Gaussian pulsed beam presenting horizontal linear polarization and a time duration of 100 fs at full width half maximum, FWHM) is divided into two arms by a beam splitter. The reference pulse is calibrated by a standard method and collected by one of the two single-mode optical fibre port. This port can be moved in the propagation direction in order to adjust a certain delay \(\tau _{{\mathrm{XR}}}\) between the arms of the reference and the unknown beam (x projection), needed for the implementation of the spatiotemporal measurements. The beam in the other arm (unknown beam arm) is shaped by a beam shaper made of an s-waveplate, a multiple-order quarter-waveplate introducing a certain delay \(\tau _{{\mathrm{PG}}}\) between the horizontal and vertical polarization components, and a zero-order quarter waveplate (the last two to create the polarization gate). The x and \(y\) components of the polarization shaped (unknown) beam are delayed with a birefringent plate, introducing a delay \(\tau _{{\mathrm{YX}}}\) for the polarization resolved measurements. The unknown beam is spatially scanned with an optical fibre port, that is recombined with the reference beam by means of a fibre coupler. The x projection spectrally interferes with a known reference pulse, while the \(y\) and x components spectrally interfere after a 45° linear polarizer. Inset polarization ellipse: scheme of the polarization ellipse defined through the polarization azimuth angle \(\chi\) and the ellipticity \(\varepsilon' = b/a\). Inset coordinate axes: the unknown beam propagates in the z-axis, the x- and y-axes are defined in the transverse plane, where the azimuthal coordinate \(\theta\) is measured with respect to the x-axis.