vHere, we consider the possibility of involving the photo-EMF detectors in registration of the parameters peculiar to ultrashort
optical pulses, and it is compared whit the recently triple correlator via Direct and Cascade Third Harmonic
Generation. Knowledge of triple auto-correlation function, whose Fourier transformation shapes the corresponding
bispectrum, makes possible recovering such train-average parameters as, for instance, the pulse width and frequency
chirp as well as revealing asymmetry of ultra-short pulse envelope. The main advantage of applying the photo-EMF
detectors lies in an opportunity to detect triple correlations directly, without any intermediate frequency conversion with
optical nonlinear processes in additional crystals. Then, the theory of three-beam-correlations at photosensitive layer of
the photo-EMF detector is developed, so that principal possibility of registering the high-order-correlations is
demonstrated. It can be done within schematic arrangement including the three-beam Michelson interferometer, so that
the obtained high-order-correlations have non-traditional form and need rather specific algorithm for their further
processing. Also, the experimental characterizations are presented for gallium arsenide (GaAs) semiconductor and the
poly-fluoren 6-co-triphenyldiamine (PF6-TPD) photo-conductor-polymer, which both exhibit the photo-EMF-effect.
They both exhibit high-pass transfer functions that give us high vibration stability. This novel approach provides more
reliable analyzing train-average parameters of picosecond pulses due to significantly higher level of the output optical
signals under processing.