Attosecond Wave Packet Metrology

Abstract: Attosecond pulses allow the study of electrons on their natural timescale. They are created from the interaction of atoms with ultrashort, intense laser pulses whose electric field approaches the strength of inner-atomic electric fields. This thesis presents experiments around the generation, characterization and application of attosecond pulses. First, we study the influence of the atomic generation medium on the temporal properties of attosecond pulses. Their central photon energy can be controlled by using a two-color generation field and by thin-foil filtering techniques tailored to specific spectral bands. With these techniques, broadband attosecond pulses with durations down to 130 as have been measured. To characterize attosecond pulse trains at their birth, we introduce a new method that perturbs the generation laser field with its weak second harmonic. This allows us to assess the influence of the medium in the generation process. We then test the limits of a well-established pulse train characterization method with regard to probe intensity and demonstrate a way to circumvent these limitations. A second set of experiments uses attosecond pulses to excite atoms and molecules for the creation of ultrashort wave packets. Free electron wave packets can be controlled by an external laser field and driven to scatter off their parent ions. They also carry information on the atomic structure, which enables the phase-resolved characterization of unknown bound wave packets. Exposing molecules to attosecond pulses can trigger dissociation reactions that can be controlled by a delayed probe laser pulse. We present a study of different probe pulse properties and report the observation of attosecond electron dynamics inside a hydrogen molecule.