Amplitude and phase characterization of weak blue ultrashort pulses by downconversion

We present difference-frequency generation cross-correlation frequency-reso lved optical gating, a new method of characterizing the amplitude and phase of weak ultrashort pulses in the blue spectral region. The method uses the spectrally resolved downconversion signal of the blue pulse and a fully ch aracterized reference pulse with a lower center frequency. The amplitude an d phase of the blue test pulse are retrieved from the corresponding spectro gram and electric field of the reference pulse with an interactive Fourier- transform algorithm. (C) 1999 Optical Society of America.