Figure 2

(a) Variation of the measured intensity width W_M with q (open red squares). Inset: comparison between the intensity profiles for q = 23 (open orange diamonds) and q = 41 (filled pink triangles). A Gaussian fit to q = 41 is shown by the brown line. (b) Variation of harmonic coherence width with q (open blue diamonds). A fit to orders 27–43 of the 1/q dependence predicted by the VCZ theorem is shown by the solid mauve line. The normalised coherence width ζ is plotted on the right hand axis with grey circles. Inset: CCF magnitude for q = 41 (filled purple triangles) with a Gaussian fit (light blue solid line). The open grey diamonds show the CCF magnitude for q = 23. (c) The measured wavefront curvature R_M−Z_GM is plotted as a function of q (open green squares). Inset: Spatial phase profile of order q = 41 (open dark green diamonds) with a fitted parabola (turquoise solid line). The same quantity for q = 23 is shown with filled yellow triangles. The error bars are smaller than the symbol size for all data points.