Generation of 3.8 fs pulses from adaptive compression of a cascaded hollow fiber supercontinuum.

We demonstrate generation of 3.8-fs pulses with energies of up to 15 ?J from a supercontinuum produced in two cascaded hollow fibers. Ultrabroadband dispersion compensation was achieved through a closed-loop combination of a spatial light modulator for adaptive pulse compression and spectral-phase interferometry for direct electric-field reconstruction (SPIDER) measurements as feedback signal.