Bright isolated light pulses reaching 18 attoseconds from high-order harmonic generation by post-compressed Yb lasers

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Abstract
Generating ever-shorter and brighter light pulses is a central goal of ultrafast science, enabling coherent control and observation of electron dynamics on their natural timescale. State-of-the-art isolated attosecond pulse generation currently achieves pulse durations of 40-50 attoseconds. Here we demonstrate isolated attosecond light pulses with durations of 18 attoseconds, via high-order harmonic generation driven by a post-compressed industrial-grade Yb laser system. The high-harmonic spectrum spans photon energies from 50 to 320 eV, covering the carbon K-edge, with a calibrated photon flux exceeding 1012 photons per second. Pulse durations were characterized by angle-resolved photoelectron streaking in helium and optimized using a series of filters with different thicknesses to compensate the attochirp. We further developed a robust, fast-converging pulse-retrieval algorithm capable of reconstructing broadband isolated attosecond pulses and double pulses. These results establish Yb-laser-driven high-order harmonic generation as a powerful platform for bright isolated attosecond sources and next-generation ultrafast spectroscopy.