The filtering, steering and control of attosecond XUV pulses from HHG requires
customised soft X-ray multilayer optics with unprecedented layer thickness and atomic interface accuracy. These multilayer optics are fabricated on superpolished glass surfaces by dual ion beam deposition at UHV in combination with in-situ spectral ellipsometry for process control on the Angstrom scale. Characterisation of the multilayer systems is performed by hard-X-ray diffractometry, transmission electron microscopy (collaboration with T. Bein, LMU Großhadern) and soft-X-ray reflectometry (collaboration with E. Gullikson, LBL/ALS Berkeley).
The temporal pulse response of the multilayer optics is experimentally accessed by using them for reflecting attosecond XUV pulses that are fully characterised via attosecond streaking followed by FROG-CRAB pulse retrieval. Stimulated by the7ongoing progress of HHG sources towards higher photon energies, we plan to extend our work to new spectral ranges in the soft-X-ray range; first to the “water-window” (280-550 eV photon energy) and later even beyond (--> 1 keV). This requires the investigation of new layer materials as well ultrathin few atomic layer systems with ~ 1 nm layer thickness, layer numbers of several hundreds and with atomic (< 0.2 nm) interface precision. Furthermore, new optics for nano-focusing of attosecond pulses based on diffractive multilayer optics (C.1.1) are being developed by electron beam lithography followed by multilayer deposition and lift-off resulting in three dimensional diffractive nanostructures. These developments will benefit all attosecond experiments (B.1.2 – B.1.5, B.3.3) and extend the frontiers of attosecond science.