Scaling and Gating Attosecond Pulse Generation

Abstract: High-order harmonic generation (HHG) provides the basis for attosecond light sources delivering coherent pulses in the extreme ultraviolet spectral region. Such light sources are employed for a variety of applications within imaging, attosecond spectroscopy, and high-precision frequency metrology. However, the rather low efficiency of the HHG process, which implies a limited pulse energy and repetition rate, places restrictions on many applications. In this thesis, the scaling of different parameters controlling the generation conditions for HHG in gases is analyzed. A general scaling model is developed, which allows scaling of the pulse energy and repetition rate of attosecond sources over many orders of magnitude, while maintaining temporal and spatial pulse characteristics. The scaling model is applied to different attosecond beam lines, which were developed and built as part of this thesis work. This includes a high-repetition rate (200\,kHz) beam line used for photoelectron emission microscopy applications, and an intense harmonic beam line delivering pulses with up to 3 µJ in the extreme ultraviolet, which was used for coherent imaging as well as for nonlinear spectroscopy applications. In addition, microscopic sub-cycle control mechanisms based on multi-color field synthesis are studied, as well as noncollinear generation geometries. It is shown that a noncollinear geometry can be used to angularly streak attosecond pulse trains, allowing access to single pulses within the train. This technique is of interest for attosecond pump-probe measurements as well as for isolated attosecond pulse generation inside an optical cavity, a scheme that promises attosecond pulses at unprecedented power levels and repetition rates.