Spatio-spectral structures in high harmonic generation driven by tightly focused high repetition rate lasers

Aura Inés Gonzalez (1, 2, 3) , Gaëtan Jargot (4, 3) , Philippe Rigaud (3) , Loic Lavenu (5, 3) , Florent Guichard (5) , Antoine Comby (6) , Thierry Auguste (7, 1) , Olivier Sublemontier (8) , Michel Bougeard (9, 1) , Yoann Zaouter (5) , Patrick Georges (3) , Marc Hanna (3) , Thierry Ruchon (7, 1)

1 LIDYL - Laboratoire Interactions, Dynamiques et Lasers (ex SPAM)
2 Amplitude Technologies
3 Laboratoire Charles Fabry / Lasers
4 FASTLITE - Ultrafast scientific Instrumentation
5 Amplitude Systèmes
6 CELIA - Centre d'Etudes Lasers Intenses et Applications
7 ATTO - Attophysique
8 LEDNA - Laboratoire Edifices Nanométriques
9 SLIC - Serveurs Laser

We investigate the spatio-spectral properties of extreme ultraviolet (XUV) high harmonic radiation driven by high repetition rate femtosecond laser systems. In the spatio-spectral domain, ring-shaped structures at each harmonic order associated with long-trajectory electrons are found to form arrow-shaped structures at the cutoff. These structures are observed with two different laser systems: an optical parametric chirped-pulse amplifier system at a central wavelength of 1.55 μm and 125 kHz repetition rate, and a temporally compressed femtosecond ytterbium fiber amplifier at 1.03 μm wavelength and 100 kHz repetition rate. As recently pointed out, the observed structures are well explained by considering the space–time atomic dipole-induced phase for short and long electron trajectories in the generation plane. The tighter focusing geometry and longer wavelength associated with these emerging driving laser systems increase the ring-like divergence and spectral broadening for high harmonics. Cutoff energies and photon fluxes obtained in argon and neon are also reported. Overall, these results shed new light on the properties of XUV radiation driven by these recently developed high average power laser systems, paving the way to high photon-flux XUV beamlines.

Mots clés: Ultrafast lasers; Ultrafast nonlinear optics; extreme ultraviolet (EUV); soft x-rays

Domaines: Optique [physics.optics]

Aura Inés Gonzalez, Gaëtan Jargot, Philippe Rigaud, Loic Lavenu, Florent Guichard, et al.. Spatio-spectral structures in high harmonic generation driven by tightly focused high repetition rate lasers. Journal of the Optical Society of America B, 2018, 35 (4), pp.A6-A14. ⟨10.1364/JOSAB.35.0000A6⟩. ⟨cea-01788352⟩