Phase-matched high-order harmonic generation in pre-ionized noble gases

O Finke (1, 2) , J Vábek (1, 2, 3) , M Nevrkla (1, 2) , N Bobrova (2) , O Hort (1) , M Jurkovič (1, 2) , M Albrecht (1, 2) , A Jančárek (1, 2) , F Catoire (3) , Stefan Skupin (4) , J Nejdl (1, 2)

1 FZU / CAS - Institute of Physics of the Czech Academy of Sciences
2 FJFI CTU - Faculty of Nuclear Sciences and Physical Engineering [Prague]
3 CELIA - Centre d'Etudes Lasers Intenses et Applications
4 iLM - MMCI - iLM - Modélisation de la matière condensée et des interfaces

One of the main difficulties to efficiently generating high-order harmonics in long neutral-gas targets is to reach the phase-matching conditions. One issue is that the medium cannot be sufficiently ionized by the driving laser due to plasma defocusing. We propose a method to improve the phase-matching by pre-ionizing the gas using a weak capillary discharge. We have demonstrated this mechanism, for the first time, in absorption-limited XUV generation by an 800 nm femtosecond laser in argon and krypton. The phase-mismatch control ability of our method is confirmed by an analytical model and numerical simulation of the complete generation process. Our method allows increasing the efficiency of the harmonic generation significantly, paving the way towards photon-hungry applications of these shortwavelength compact sources.

Domaines: Physique des plasmas [physics.plasm-ph]; Physique Atomique [physics.atom-ph]; Optique [physics.optics]

O Finke, J Vábek, M Nevrkla, N Bobrova, O Hort, et al.. Phase-matched high-order harmonic generation in pre-ionized noble gases. Scientific Reports, 2022, 12, pp.7715. ⟨10.1038/s41598-022-11313-6⟩. ⟨hal-03583906v2⟩