@phdthesis{Selle2007,
  author    = {Selle, Reimer Andreas},
  title     = {Adaptive Polarization Pulse Shaping and Modeling of Light-Matter Interactions with Neural Networks},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-25596},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2007},
  abstract  = {The technique of ultrafast polarization shaping is applied to a model quantum system, the potassium dimer. The polarization dependence of the multiphoton ionization dynamics in this molecule is first investigated in pump-probe experiments, and it is then more generally addressed and exploited in an adaptive quantum control experiment utilizing near-IR polarization-shaped laser pulses. The extension of these polarization shaping techniques to the UV spectral range is presented, and methods for the generation and characterization of polarization-shaped laser pulses in the UV are introduced. Systematic scans of double-pulse sequences are introduced for the investigation and interpretation of control mechanisms. This concept is first introduced and illustrated for an optical demonstration experiment, and it is then applied for the analysis of the intrapulse dumping mechanism that is observed in the excitation of a large dye molecule in solution with ultrashort laser pulses. Shaped laser pulses are employed as a means for obtaining copious amounts of data on light-matter interactions. Neural networks are introduced as a novel tool for generating computer-based models for these interactions from the accumulated data. The viability of this approach is first tested for second harmonic generation (SHG) and molecular fluorescence processes. Neural networks are then utilized for modeling the far more complex coherent strong-field dynamics of potassium atoms.},
  subject      = {Lasertechnologie},
  language  = {en}
}
@phdthesis{Walter2006,
  author    = {Walter, Dominik},
  title     = {Adaptive Control of Ultrashort Laser Pulses for High-Harmonic Generation},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-21975},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2006},
  abstract  = {The generation of high harmonics is an ideal method to convert frequencies of the infrared- or visible range into the soft x-ray range. This process demands high laser intensities that are nowadays supplied by femtosecond laser systems. As the temporal and spatial coherence properties of the laser are transferred during the conversion process, the generated high harmonics will propagate as a beam with high peak-brightness. Under ideal conditions the generation of soft-x-ray pulses shorter than one femtosecond is possible. These properties are exploited in many applications like time-resolved x-ray spectroscopy. The topic of this thesis is the generation and optimization of high harmonics. A variety of conversion setups is investigated (jet of noble gas atoms, gas-filled hollow-fiber, water microdroplets) and theoretical models present ideas to further enhance the conversion efficiency (using excited atoms or aligned molecules). In different setups the peak intensity of the fundamental laser pulses is increased by spectral broadening and subsequent temporal compression. This is achieved with the help of pulse shaping devices that can modify the spectral phase and therefore also the temporal intensity distribution of laser pulses. These pulse shaping devices are controlled by an evolutionary algorithm. With this setup not only adaptive compression of laser pulses is possible, but also the engineering of specific laser pulse shapes to optimize an experimental output. This setup was used to influence the process of high harmonic generation. It is demonstrated that the spectral distribution of the generated soft-x-ray radiation can be controlled by temporal pulse shaping. This method to tailor high harmonics is complemented by spatial shaping techniques. These findings demonstrate the realization of a tunable source of soft-x-ray radiation.},
  subject      = {Frequenzvervielfachung},
  language  = {en}
}