High-order Harmonic Generation and Visualization of Phase Matching

• Main Author: Dempsey, Dennis
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2020
• Subjects: Optics
• ISBN: 9798664701302

High Harmonic Generation (HHG) is the process in which multiple photons are simultaneously absorbed and a single photon is emitted at a much higher frequency. This process is useful for generation of ultrashort, coherent ultraviolet and soft X-ray light that can be potentially used for tabletop particle accelerators, probing material properties, as well as a new regime of ultrashort time measurements into the attosecond regime (10$^{-18}$s). This process suffers from low efficiency often with conversion efficiencies of 10$^{-5}$ and instability. As a result much research has and continues to be performed in the optimization of high harmonic generation as well as theoretical studies of the underlying physics. The well accepted theory introduced to describe high harmonic generation in gasses is the three step model which includes tunneling ionization, acceleration of the free electron and eventual recombination with increased kinetic energy. Since this process depends critically on free electron creation and recombination, which often happen on picosecond and femtosecond timescales, there is a need to visualize the process to develop a better understanding of the nonlinear dynamics involved. I present a potential future study that will probe these dynamics of HHG using a technique called Frequency Domain Holography (FDH), which allows us to measure time evolving structures on the femtosecond timescale and diffraction-limited spatial resolution in a single shot.