Sub-5-fs transform-limited visible pulse source and its application to real-time spectroscopy

Transform-limited (TL) visible pulses with as short a duration as 4.7 fs with a 5-μJ pulse energy have been generated for the first time from a novel noncollinear optical parametric amplifier. Both signal-idler group-velocity matching and pulse-front matching are essential to generate coherent down-converted pulses compressible to the TL pulse with more than 150 THz bandwidth. Tunable operation with bandwidth-limited sub-10-fs pulses in the visible (550-700 nm) and near-infrared (900-1300 nm) ranges, achieved by increasing the seed chirp, is also a marked property. Applications for ultrafast spectroscopy of the sub-5-fs pulse source to the real-time spectroscopy of conjugated polymer, a dye molecule, and J-aggregates are also described