Mainz 2026 – wissenschaftliches Programm

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K: Fachverband Kurzzeit- und angewandte Laserphysik

K 3: THz, EUV and X-Ray Sources and their Application

K 3.1: Vortrag

Montag, 2. März 2026, 17:45–18:00, HS 20

Overdriven High-Harmonic Generation in a Sub-mm Glass-Chip — •Linda Oberti for the HHG in glass-chip collaboration — Centre for Free-electron Laser Science, Deutsches Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg, Germany — Institute for Photonics and Nanotechnologies, Consiglio Nazionale delle Ricerche, piazza L. da Vinci 32, 20133 Milano, Italy — Physics Department, Politecnico di Milano, piazza L. da Vinci 32, 20133 Milano, Italy

Attosecond light sources based on high-harmonic generation provide a table-top route to coherent broadband radiation from the extreme ultraviolet to the soft X-ray region. One approach to extending the harmonic cutoff is to increase the driving wavelength, though this reduces conversion efficiency. Alternatively, the overdriven regime can be accessed at the same wavelength, requiring precise control of plasma formation over sub-millimeter distances. We address this challenge using a newly designed differentially pumped glass-chip target that ensures efficient gas confinement on sub-mm scales. Driven with multicycle near-infrared pulses at 800 nm and 1500 nm, it enables a cutoff extension up to a factor of two compared with conventional phase-matching geometries. Three-dimensional propagation simulations reproduce the experimental results and reveal that efficient phase matching of cutoff harmonics is achieved only in short media. They also show that plasma-induced reshaping of the driving field confines high-energy emission to the leading edge of the pulse and directs it off-axis in the near field. These results clarify key mechanisms governing overdriven HHG and demonstrate the importance of strong gas confinement.

Keywords: HHG; Soft-x rays; gas confinement; Non adiabatic regime; phase matching