Abstract

Growing demands for high average and peak powers in extreme nonlinear optics, attosecond-pulse and extreme ultraviolet comb generation experiments can find a powerful solution in fibre-based mode-locked lasers. Using passive enhancement cavities, fibre lasers have produced high-repetition-rate femtosecond pulse trains with multikilowatt average powers and peak powers reaching hundreds of megawatts. One major challenge for novel high-resolution spectroscopy and precision measurement in suboptical wavelength regions is to transfer the state-of-the-art optical phase coherence into the extreme ultraviolet domain through the extreme nonlinear optics enabled by these high-power systems. We demonstrate here that optical frequency combs produced by high-power fibre lasers reach unprecedented levels of performance in both precision and average power. We achieve a record low relative linewidth of mHz between a traditional Ti:sapphire frequency comb and a novel 10|[nbsp]|W average power fibre comb, at the same time demonstrating all the necessary elements for power scaling precision comb technology to beyond 10|[nbsp]|kW.