The temporal confinement of laser light pulses to durations approaching the optical period, and the subsequent conversion of these pulses into extreme ultraviolet and x-ray wavelengths through the process of high-order harmonic generation (HHG), has enabled measurement and control of ultrafast processes spanning picosecond to attosecond timescales. Typically achieved by nonlinear compression of multi-cycle pulses in gas-filled hollow-core fibers, compression to single-and even sub-cycle durations is now becoming routine due to the availability of state-of-the-art Ti:sapphire laser amplifiers outputting millijoule level pulses with pulse durations below ten cycles. Even so, reliance on mJ-level Ti:sapphire lasers has in most cases limited repetition rates to the few kilohertz regime, therefore restricting their application to time-resolved spectroscopies for which high repetition rates are needed. Toward this end, nonlinear compression of Yb-doped solid state and fiber sources, for which small quantum defect allows for high average powers, has garnered considerable attention in recent years. In this dissertation, I investigate the spectral broadening and temporal compression of sub-millijoule, 280 femtosecond pulses from a high average power Yb-doped laser amplifier by nonlinear compression in gas and solid media. The application of these pulses to high-repetition rate time-resolved studies is further established through their use in both HHG and time- and angle-resolved- photoemission spectroscopy. Moreover, I demonstrate the ability to harness the delayed nonlinearity of molecular gases to obtain multi-octave spectral broadening from pulses with long input durations and achieve compression to sub-two cycle durations. The fidelity of the sub-two cycle pulses is demonstrated through the generation of a high-order harmonic XUV continuum, suggesting a path to perform attosecond measurements with commercial laser systems. Finally, I investigate the potential to extend this technique to high average powers by studying the effects of nonequilibrium rotational state distributions in the repetitively laser-heated molecular gas on the supercontinuum spectrum.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Beetar, John, "Tunable Few- to Many-Cycle Source for High-Order Harmonic Generation and Time-Resolved Spectroscopy" (2020). Electronic Theses and Dissertations, 2020-. 327.