Direct interferometric techniques for characterizing ultrashort optical pulses

The two-time nonstationary correlation function is defined and applied to the problem of characterizing pulses whose amplitude and phase vary randomly from pulse to pulse. Using a linear-systems approach developed in earlier work, four simple interferometric techniques for measuring this quantity are described and analyzed. We show that these four methods offer simple and direct algorithms for reconstructing the correlation function and, in the case of a single pulse or a coherent ensemble of pulses, return the electric field amplitude and phase.