Extended Data Fig. 1: Isosurfaces in 3D space of a helical wave packet synthesized experimentally.
From: Broadband control of topological–spectral correlations in space–time beams
The corresponding topological-spectral correlation of this beam is shown in Fig. 2e. Here, the temporal coordinate is replaced by the z-propagation coordinate, as we obtain from hyperspectral off-axis holography the space-time beam propagation at different times: a, t = 0; b, t = 67 fs, corresponding to a beam propagation of 20 μm; c, t = 167 ps, corresponding to a beam propagation of 5 cm. Apart from a very small lateral shift, the beam essentially translates along the z-axis as it propagates (in the direction marked by the red arrow in a). Due to its helical structure, at a given z-plane the space-time beam appears as a pulse that rotates over time on a circular trajectory, as shown in the space-time isosurface of Fig. 2f. The isosurfaces are defined at 10% of the intensity peak.
