Sayrac, Muhammed (2017-01). High Harmonic Generation Optimization in Atomic and Molecular Gases. Doctoral Dissertation. Thesis uri icon


  • High harmonic generation (HHG) is a unique process in which atoms/molecules ionized by an intense laser field at frequency ?0 emit radiation of higher frequencies, which are multiples of frequency ?0, at much shorter wavelengths ranging from the ultraviolet to the soft x-ray region (XUV region). These so-called high harmonics (HHs) are very promising for spectroscopic and imaging applications since HHs possess high spatial and temporal coherence. Unfortunately, HHG suffers from its low conversion efficiency of the driving radiation (usually in the IR region) to the XUV range. This dissertation reports experimental works based on the HHG technique. In this work, we present different experimental approaches, which enhance the output of the HHG radiation, i.e. the conversion efficiency. In the first approach, a differentially pumped gas cell is used to control the pressure in the interaction region. This approach allows us to optimize the efficiency of the HHs yield by finding the optimum atomic/molecular density, taking into account also the absorption and phase matching conditions. In the second approach, gas mixtures of Ne with H2 are investigated to improve the conversion efficiency of the HHs output. In the third approach, an enhancement of HHs radiation in aligned molecules is investigated. In the fourth approach, the enhancement of even and odd harmonics in a two-color laser field is explored. Finally, the application of the XUV radiation, obtained via HHG with the goal to improve the spatial resolution of imaging of the nano- to micron sized structures is presented.

publication date

  • May 2017