Pushing the frontiers of attosecond metrology and spectroscopy

Here we proposed two routes – which eventually will combined together – for pushing the frontiers of attosecond metrology and spectroscopy. The first will be to extend isolated attosecond pulses towards photon energies of the order of 1 keV. Such pulses will provide access to K-shell electrons in constituents of biological and magnetic matter and pave the way towards combining atomic resolution in space and time. Moreover, the enhanced photon energies (> 150 eV) will be instrumental in extending attosecond spectroscopy to surfaces and solids (C.1.4, C.1.5, C.1.7). By driving the process with LWS-1 (λ carrier = 2.1 μm, A.1.3), we expect to extend it into the keV regime with a better efficiency. This is because the generation of the same or higher-harmonic photon energies will be possible at much lower field strengths owing to the quadratic scaling of the maximum harmonic photon energy (cut-off) with the driving laser wavelength. The second route will be to increase the HHG photon flux. An intense XUV source will provide access to nonlinear phenomena in the XUV regime and for some XUV-pump XUV-probe experiments. Here we plan to use a few cycle, high energy laser (20 TW, λ carrier~750 nm) in the loosely focusing geometry to enhance the conversion efficiency due the low Gouy phase mismatch, which enable longer interaction length. Further enhancement of the conversion efficiency will be carried out by means of quasi phase matching (QPM) technique with multi gas jet target (see photo). The combination of high-power few cycle laser with the high conversion efficiency into the high harmonics affords promise for providing isolated attosecond XUV/SXR pulses with microjoule energies, implying peak powers comparable to those available from FLASH at DESY.