Fig. 4

Measuring interference between an XUV vector beam and a XUV reference beam. a Experimental setup. The polarization of the reference beam is controlled by a half-wave plate (HWP) for the fundamental. The XUV beams are spectrally resolved and spatially overlapped in an XUV spectrometer. The interference images are recorded by the micro-channel plate (MCP). b Interference between the XUV reference and vector beam. The blue curve shows the fringes when the reference beam is p-polarized, and the green curve shows the fringes when the reference beam is s-polarized. The dotted red lines indicate periods of the modulation. All the red dotted lines aligned with all the peaks of the green curve, which indicates the s-component at intersections are all in phase. For the p-component shown with the blue curve, either the peaks or the valleys are aligned with the red dotted line, and that indicates p-components at intersections that are out of phase with respect to the adjacent one