High dynamic range characterization of ultrabroadband white-light continuum pulses

We demonstrate an improved method for characterizing ultrashort pulses. Our apparatus is based on spectral phase interferometry for direct electric-field reconstruction (SPIDER) and particularly suited for measurement of compressed white-light continuum pulses with their strong spectral amplitude variations. Phase-sensitive noise rejection allows for a significant increase of the dynamic range of the SPIDER trace. We show that characteristic SPIDER artifacts can be avoided and demonstrate the method by characterizing 4.3-fs pulses from a two-stage hollow-fiber compressor.