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Abstract:
The generation of energetic laser pulses with durations below one optical cycle is one of the current frontiers of ultrafast optics. Such sources attract enormous attention due to the implications they hold for studying extreme light-matter interactions and to harness attosecond pulse production via high harmonic generation (HHG). This thesis presents the implementation of a parallel parametric waveform synthesizer which generates sub-cycle pulses of light spanning more than two octaves of spectral bandwidth (500 nm to 2.2 µm) by coherent combination of individual ultra-broadband OPA sources covering different spectral ranges in the visible, near-infrared and infrared. The parallel approach to parametric waveform synthesis offers unique scaling potential with respect to bandwidth and pulse energy and it provides several control knobs to custom-sculpture the synthesized light-field transient. Challenges of the parallel scheme are the required active timing stabilization and control system to stabilize such a complex multi-path interferometer to sub-cycle precision and to custom-sculpture the synthesized waveform. In the frame work of this thesis, several techniques to implement such a complex experiment with enhanced mechanical stability were demonstrated and furthermore this thesis introduces and demonstrates the first full timing control system for such a synthesizer. This includes newly developed optical timing tools, for which an active timing synchronization down to few tens of attoseconds is demonstrated. Furthermore, unique FPGA-based timing sensors were developed and allow to gain a deeper understanding of the timing and phase dynamics in such parametric sources. A novel scheme for carrier-envelope phase stable multi-octave-wide seed generation is also proposed and experimentally investigated. These efforts allowed for the very first controlled HHG driven with sub-cycle pulses from such a parallel parametric waveform synthesizer. A full characterization of these novel pulses via attosecond streaking to fully recover the electric field transient of the synthesized waveform is ongoing. The synthesized pulse has a center wavelength of 1.8 µm and aims for efficient isolated attosecond pulse (IAP) production up to the water-window (284 eV - 543 eV). This source can be scaled potentially beyond the mJ-level of pulse energy by using novel pump laser technologies, which holds great potential for attosecond science.
