Pulse characterization via two-photon auto- and cross-correlation

We present the application of a previously proposed multiple-Gaussian approach to characterize ultrashort vacuum (VUV) and deep ultraviolet (DUV) pulses via auto- and cross-correlation methods. The knowledge of the temporal variation of amplitude and phase of such pulses is important for spectroscopic and dynamical imaging techniques. The method, which is an extension of the single Gaussian autocorrelation technique, is based on the expansion of the pulse in a series of Gaussian functions at different frequencies and the use of analytic solutions for two-photon ionization of atoms by Gaussian pulses. Using this approach we compare the characterization of a pulse via the auto- and the cross-correlation techniques and find that an accurate characterization even in the case of more complex pulse forms can be achieved. Furthermore, the comparison of the application of unchirped and chirped Gaussian pulses reveals some specific advantages in the use of pulses with a linear chirp. Finally, we quantify our conclusions from the qualitative comparisons by defining errors and using results from information theory.