High-order Harmonic Generation (HHG)

The mechanism of high-order harmonic generation in gas will be employed in a kHz beam line of ultra-short pulses of tunable coherent EUV–soft X-ray radiation that will be installed in the E1 hall of the ELI Beamlines facility.

Generation of high-order harmonics of an intense laser pulse is now widely considered to be an efficient source of ultra-short pulses in the spectral range from EUV to soft X-rays. The atoms of noble gases interacting with a strong laser field (1014-1015Wcm-2) are likely to be partially ionized and the freed electrons are first accelerated and then rescattered from the parent ion while generating radiation of short wavelength in attosecond bursts repeating every laser cycle. The coherent addition of this radiation from a significant target volume through phase matching (or quasi-phase matching) leads to a substantial increase in the power that is generated.

Using the L1 laser driver (100mJ in 20fs at 1kHz) with long-focusing geometry and a two-color driving scheme will allow for an mW-level beam of fully coherent radiation in the spectral range from 5 to 120nm that can be synchronized to a VIS/IR laser beam or plasma X-ray source with femtosecond precision. The ability to provide two independent fully synchronized beams of HHG is also foreseen in monochromatic or “multi-color” modes within this beam line.

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