Filamentation-assisted isolated attosecond pulse generation

The advancement of attosecond science relies on achieving stable generation of isolated attosecond pulses (IAPs), which are essential for capturing ultrafast dynamics in atoms, molecules and solids. Our study in an extended gas medium demonstrates filamentation-assisted spatiotemporal reshaping of the infrared driving pulse, enabling transient phase-matching gating and the generation of bright, high-contrast IAPs. Our experimental and theoretical results reveal that a semi-infinite gas cell naturally forms a stable propagation region, where the driving pulse undergoes controlled self-compression and spatial cleaning. In an argon-filled gas cell, filamentation reduces the duration of Ytterbium-based 1030 nm pulses from 4.7 fs to 3.5 fs, while simultaneously producing high-contrast IAPs of 200 as, at 65 eV, with an excellent output beam profile. Similar filamentation-assisted transient gating is observed in neon and helium, yielding pulses of 69 as at 100 eV and 65 as at 135 eV. This filamentation-enabled transient phase-matching mechanism opens a simple and robust route to provide high-contrast attosecond sources, advancing both post-compression techniques and attosecond-based technologies.