Ion-Based Hard X-Ray High-Harmonic Generation with a Transverse Disruptive Pulse for Quasi-Phase-Matching

Recognized by the 2023 Nobel Prize in Physics, high-harmonic generation (HHG) from laser-irradiated gases or solids has been established as a reliable, coherent light source with ultrashort durations and wavelengths. Achieving shorter wavelengths demands higher laser intensity, but this increases the ionization ratio and causes severe phase mismatch. Traditional phase-matching methods are ineffective in a highly ionized medium, making the efficient generation of high harmonics at short wavelengths a persistent challenge.