Spatio–spectral structures in high-order harmonic beams generated with Terawatt 10-fs pulses

Abstract

A large international effort is nowadays devoted to increase the energy of the extreme ultraviolet pulses by using high-peak power ultrashort fundamental pulses (Terawatt level). Using such fundamental pulses brings specific constraints that need to be addressed. Here we study high-order harmonic generation in gases with 10 fs pulses at Terawatt peak power and demonstrate that extreme ultraviolet beams can be highly structured and complex in various conditions. We use a single-shot spatially resolved spectral detection and demonstrate direct observation of the spatio-temporal coupling occuring in the generating medium. Clear and reproducible complex spatio-spectral structures are observed in the far field. Similar structures are reproduced with simulations and we show that they are intimately associated to the high nonlinearity of high-order harmonic generation. Those findings are of prime importance for the generation of high-energy attosecond pulses and reveal important issues for their applications.

Spectrally resolved spatiotemporal features of quantum paths in high-order-harmonic generation

“…The single-atom dipole phase is naturally coupled with the macroscopic response, which leads to different phasematching and therefore rich spatial and spectral features of HHG [18]. Thus, in turn, the spatial and spectral features offer useful information on the HHG process [19,20] and the gas medium [21].…”

Macroscopic scaling of high-order harmonics generated by two-color optimized waveforms in a hollow waveguide

“…We anticipate this study to inspire further interest in studying macroscopic HHG scaling in other guided geometries, free geometries, or beam truncated geometries [50,51] by using single-or multicolor laser pulses.…”

Compression of TW class laser pulses in a planar hollow waveguide for applications in strong-field physics

“…It might result from blueshifting of the fundamental on-axis due to high ionization yield [30]. In addition, the transversely varying spectrum and pulse duration of the waveguide output can potentially lead to complicated spatio-temporal couplings in combination with nonlinear propagation and the strongly nonlinear dynamics of the HHG process itself [31]. Although interesting in itself, a detailed interpretation of the particular shape of the harmonics is beyond the scope of this article.…”