Quasi-phase-matched 1-keV high-order harmonic generation with subcycle temporal gating in a tailored gas-target array
Phys. Rev. A 114, 033119 – Published 29 September, 2026
DOI: https://doi.org/10.1103/9zpv-995s
Abstract
We present a quasi-phase-matched (QPM) high-order harmonic generation (HHG) scheme based on a segmented gas target array for the generation of keV harmonics. By optimizing the gas density and intersegment spacing, the total phase mismatch arising from plasma dispersion, geometrical phase shift, and dipole phase variation is locally balanced within each gas segment. Compared with a single-segment configuration, this approach yields an eightfold enhancement in harmonic output. Furthermore, the time-dependent phase-matching condition produces subcycle temporal gating of the harmonic emission. For a 15-fs near-infrared driving pulse, a gating window of approximately 0.9 fs is obtained, with the emission dominated by a single HHG burst. The corresponding QPM bandwidth supports an attosecond-scale transform limit, estimated to be approximately 151 as under ideal spectral-phase compensation.
