CRAB-and VAMPIRE-Techniques

The basic principle of CRAB (complete reconstruction of attosecond bursts) is shown in Fig. 6.59. 

Further information can be obtained from measurements of the energy spectrum of the photo-electrons. A weak low frequency laser field is applied to the interaction 

In order to remove the ambiguities of pulse analysis for the FROG technique, a self referenced two-pulse measurement technique was invented [791], which is called VAMPIRE very advanced method for phase and intensity retrieval). 

Its basic principle [779] is illustrated in Fig. 6.85. The signal beam 1 interferes in a nonlinear medium with the signal beam 2, specially prepared by a conditional filter which consists of a spectral and a temporal phase modulator. The spectral phase modulator can be realized by an unbalanced Mach-Zehnder interferometer (see Vol. 1, Sect. 4.2.4) with a dispersive element placed in one of the arms. The spectral phase modulator breaks the symmetry of the measured signal and therefore avoids ambiguities caused by symmetric VAMPIRE spectrograms. 

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