High Harmonic Generation by an Elliptically Polarized IR-Radiation on Atomic and Molecular Targets

The aim of the master thesis is to provide a theoretical study of the XUV-radiation production based on the High Harmonic Generation (HHG) in gaseous media. It focuses on two aspects: 1--temporal control using the so-called polarisation gating technique in order to reduce the pulse duration and control the spectral properties of the generated XUV and 2--studying spatial distribution of the XUV in order to confine spatially the XUV pulse. First, the theory of HHG is explained. Concerning the temporal control, the highest XUV-photon energy under the optical gating is analysed and we show an extend of the cut-off as compared to the linear case. Then, we have simulated the case where two delayed counter-rotating elliptical pulses of different amplitudes are used and we demonstrate, for the first time, that it allows for controlling the XUV-photon frequency. The spatial distribution analysis of the harmonic spectra is motivated by recent experimental observations. We have developed a model for simulating spatially resolved XUV generation in thin media. In these simulations, several microscopic response models (starting with a simple microscopic phenomenological dipole up to a fully quantum description) have been accounted showing qualitative agreement with experiments. Both aspects of HHG are essential for providing a realistic model and their common output may provide a powerful and robust tool requested for the design of experiments and also for their physical interpretation.