Abstract
Extending single attosecond pulse technology from currently sub-200 eV to the so called 'water window' spectral range may enable for the first time the unique investigation of ultrafast electronic processes within the core states of bio-molecules as proteins or other organic materials. Aperiodic multilayer mirrors serve as key components to shape these attosecond pulses with a high degree of freedom and enable tailored short pulse pump-probe experiments. Here, we report on chirped CrSc multilayer mirrors, fabricated by ion beam deposition with sub-angstrom precision, designed for attosecond pulse shaping in the 'water window' spectral range.
Highlights
Multilayer XUV/soft X-ray mirrors are key components for steering attosecond pulses from high harmonic radiation [1]
Based on the layer accuracy achieved on the periodic CrSc multilayer results, as presented in chapter 3, we have simulated and optimized a set of two different aperiodic broadband CrSc multilayer mirrors aiming for the reflection of single attosecond pulses from the high harmonic plateau in the ‘water window’ spectral range around a photon energy of 326 eV
High Harmonic Generation (HHG) sources producing single isolated attosecond pulses, with pulse durations of 80 as [8] or trains of 63 as pulses [29], are possible based on few cycle intense near-infrared (NIR) laser pulses from carrier envelope phase stabilized Ti:sapphire amplifiers, which are converted into a high harmonic spectrum ranging into the XUV spectral range by non-linear frequency conversion in a rare gas medium (e.g. Ar, Ne, He) [3,30] or solid [31,32,33]
Summary
Multilayer XUV/soft X-ray mirrors are key components for steering attosecond pulses from high harmonic radiation [1] These pulses pave the way towards the observation of electron dynamics in atoms, molecules or solid surfaces/nanostructures with an unprecedented temporal precision [2,3,4]. Previous experiments have shown that aperiodic multilayer mirrors can control the attosecond pulse dispersion around 100 eV [5,6,17] being used for resonant excitation of distinct atomic core states [18] Extending this control, into the ‘water window’ spectral range, requires multilayer optics of sub-angstrom layer precision as their spectral amplitude and phase are extremely sensitive to even the smallest thickness errors of only a fraction of the nominal layer thickness [19] being typically around 1 nm [20]. By using the measured reflectivity and calculated spectral phase data (derived from the experimental multilayer structure) the temporal response to a chirped single attosecond pulse at ~320 eV has been calculated
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