Self-imaging of tailored vortex pulse arrays and spectral Gouy rotation echoes.

Self-imaging of femtosecond pulses with orbital angular momentum is studied in spectral domain by illuminating the orthogonal arrays of spiral gratings. Spectral Gouy rotation, i.e., the characteristic circulation of extremal regions near phase singularities in spatial spectral maps, is found to partially reappear at discrete distances. The self-imaging of co-rotating and counter-rotating vortices is compared in intensity and spectral behavior. High-selectivity pattern recognition from weakly modulated spectral maps is demonstrated by analyzing spectral moments. By our experiments, the classical Talbot effect is extended to polychromatic pulsed vortex arrays with controlled maps of rotation sign.