Spatially resolved temporal coherence of few-cycle pulses without and with orbital angular monentum.
Spatially resolved temporal coherence maps obtained by second-order autocorrelation of a Gaussian and a Laguerre-Gauss beam with topological charges of (a) mSHG = 0 and (b) mSHG = 2. The distributions were derived from central cuts through the spot arrays (data corresponding to Fig. 3b). The data sets allow for a reconstruction of complete 3D temporal coherence profiles. The conservation of temporal coherence information along the selected cut direction is indicated by homogeneous spatio-temporal distributions of the pulse duration in both cases. The detailed analysis shows some slight inhomogeneities over the beam cross section (cf. Figs. 6a, b). The curvature in time indicates the wavefront curvature of the field cycles in space. The theoretical time resolution is about 0.12 fs. Insets: cut profiles along the red bows and corresponding envelope (green solid curve). The centre-to-centre distance between neighbouring sub-beams of the orthogonal beam array was about 478 μm in this experiment.