Generation of Ultrashort Pulses – From Femtoseconds to Attoseconds

Sammanfattning: Electronic dynamics takes place on the attosecond timescale and can thus only be studied using a tool with attosecond temporal resolution. High harmonic generation (HHG) provides coherent attosecond pulses in the extreme ultraviolet spectral region. The work presented in this thesis focuses on generating and characterizing ultrashort femtosecond pulses and using them for HHG, together with a gating scheme, in order to produce isolated attosecond pulses (IAPs).The first part describes the work on the generation of high-energy, few-cycle femtosecond pulses using post-compression schemes, with emphasis on gas-filled, hollow-core capillary post-compression systems. General scaling laws for nonlinear optics in gases were identified.The second part focuses on the compression and characterization of ultra-broadband femtosecond pulses with emphasis on the dispersion scan (d-scan) technique for characterization of the pulses and on the stabilization of the carrier-to-envelope offset phase. Significant improvements were made in the d-scan technique, namely, a new, faster retrieval algorithm and a novel, compact, single-shot design.The last part deals with HHG. First, a pump-probe scheme called RABBIT (reconstruction of attosecond beating by interference of two-photon transitions) is described, with emphasis on its application to measure the phase across a Fano resonance. Then, a novel gating technique, called noncollinear optical gating, allowing the generation of several, spatially separated, synchronized IAPs, is presented together with its experimental demonstration.