Compression of high-energy laser pulses below 5 fs

High-energy 20-fs pulses generated by a Ti:sapphire laser system were spectrally broadened to more than 250 nm by self-phase modulation in a hollow fiber filled with noble gases and subsequently compressed in a broadband high-throughput dispersive system. Pulses as short as 4.5 fs with energy up to 20-$\mathit{\mu }\mathrm{J}$ were obtained with krypton, while pulses as short as 5 fs with energy up to $70 \mathit{\mu }\mathrm{J}$ were obtained with argon. These pulses are, to our knowledge, the shortest generated to date at multigigawatt peak powers.