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Tuesday, 10 January 2017

17/1-2017 Allan: High Harmonic Half-Cycle Cutoffs Beyond the Oxygen K-edge

Using high harmonic generation (HHG) to make attosecond pulses in the soft X-ray (SXR) for time-resolved X-ray spectroscopy measurements is a topic of great interest. Recent work has demonstrated the first CEP dependent harmonic generation into the so-called "water window" region between 284 eV and 540 eV [1]. This region is of interest because there are numerous absorption edges of interesting atoms, while water is largely transparent, allowing in principle for invivo imaging and spectroscopy. Other recent work includes improved X-ray generation up to 500 eV [2] and time-resolved measurements at the carbon K-edge (284 eV) [3].
I'll present our work on generation of CEP dependent HHG across the water window (implicitly, attosecond pulses). We have generated HHG from neon and helium up to maximum energy of 650 eV, and can move our cutoff energy (and thus, attosecond pulse) to any absorption edge in the water window. Our source also exhibits excellent spatial quality, as demonstrated by a SWORD measurement, suggesting the potential for imaging applications and even, intriguingly, X-ray non-linear optics. We also perform the first X-ray absorption measurement with an HHG source at the oxygen K-edge (540 eV).

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