Near-transform-limited visible and near-IR femtosecond pulses from optical parametric amplification using type II β -barium borate

Type II phase-matched b-barium borate is used in the f irst stage of amplif ication of a white-light continuum in a two-stage optical parametric amplif ier pumped by the second harmonic of a regeneratively amplif ied Ti:sapphire laser system operating at 824 nm. Near-transform-limited sub-190-fs pulses with microjoule energies are achieved in the signal branch, which is tunable from 475 nm to degeneracy. This system effectively bridges the wavelength gap between the fundamental and the second harmonic of amplif ied Ti:sapphire laser systems.