Speaker: John Beetar, UC Berkeley
Program Description:
Over the last decade, Yb-based laser systems have matured into a robust, high-average power scalable technology, and their application as drivers of high-order harmonic generation (HHG) for table-top extreme ultraviolet (XUV) sources has garnered considerable attention. This work reports on the development of a tunable few- to- many- cycle source for time-resolved spectroscopies based on HHG, where prioritization of temporal or spectral resolution becomes achievable. I will present my work on the temporal compression of sub-mJ, 280 fs pulses from a high average power Yb-doped laser amplifier to few-cycle durations using multi-stage nonlinear compression in solid and gas media. Emphasis will be given to the large compression factors that can be obtained by harnessing the delayed nonlinearity of molecular gases to compress pulses with long input durations down to sub-two cycle durations. The versatility of the source is demonstrated through its use in HHG, where few-cycle pulses can be used to generate an XUV continuum, suggesting a path to perform attosecond measurements. Additionally, I’ll show how the uncompressed output can be used to obtain high spectral resolution time- and angle-resolved- photoemission spectra at high-repetition rates, allowing the characterization of nonequilibrium electronic band structures in novel quantum materials.
