Strong-Field Physics with a High Energy Waveform Synthesizer

The motivation to control and temporarily isolate a single quantum mechanical event like an electronic transition has driven the quest for ever shorter light pulses. Controlling a highly intense electric field in the visible to infrared wavelength range on a sub-cycle time scale becomes feasible with the concept of the parametric waveform synthesizer. High harmonic generation (HHG) is explored as a primary application with the aim to generate isolated attosecond pulses and high photon energies in the ”Water Window” spectral region from 284 eV to 533 eV. The tight synchronization of pulses from optical parametric amplifiers (OPAs) spanning from 650 nm to 2200 nm is achieved with long-term synthesized waveform stability. To work out and monitor the ideal synthesis parameters, a set of characterization methods are developed in the time and spatial domain.The ability to control sub-cycle fields is displayed via the large variety of XUV and soft X-ray continua as generated via HHG covering photon energies starting from 30 eV all the way upentering the ”Water Window”. The peculiarity of sub-cycle infrared driving pulses allows togenerate isolated attosecond pulses a priori without further gating techniques. The phase-stablecontrol of the driver pulse allows to shape the harmonic continua in bandwidth and central en-ergy.Characterization of both the generated isolated attosecond pulses and the synthesized infrareddriving field is performed in an attosecond streaking experiment yielding reproducible and com-pressed XUV pulses down to 80 as FWHM, including the retrieval of an ≈ 2 octaves spanningdriver pulse.A partial redesign of the vacuum apparatus to aim for high-pressure phase-matching conditionsinside the HHG gas nozzle enabled the generation of soft X-ray continua up to 450 eV. The con-tinuous spectra in neon and helium are investigated as a function of the driving waveform andmacroscopic parameters. A comparison of the pulse energies at soft X-ray bandwidths oncegenerated with the infrared OPA (two-cycle pulse) and once generated with the synthesizedpulse (sub-cycle), shows an up to 5-fold flux increase. The absolute maximum pulse energy ismeasured to 1 pJ integrated from 200 eV onwards.Finally, the design of an experimental chamber, an updated toroidal mirror and a soft X-Rayspectrometer prepare for future attosecond transient absorption experiments