
Pulse Amplitude and Phase Reconstruction 473
intensity autocorrelation. Obtaining such an intensity autocorrelation, however,
assumes that the beams coming from both arms of the correlator add construc-
tively toward the detector, destructively toward the source. Such a condition is
difficult to implement, because it requires subwavelength stability and accuracy
in controlling either arm. For this particular correlator, it is more convenient to
introduce a small tilt of either end mirror of the Michelson interferometer. Such
a tilt produces a pattern of parallel fringes at the output. Before the frequency
doubling crystal, we have thus generated a