Sub-Cycle Control of Strong-Field Processes on the Attosecond Timescale

Abstract: This PhD thesis deals with the sub-cycle nature of ultrafast phenomena that occur in strong-field light–matter interactions. As it is of interest to control these phenomena, we must understand them in order to manipulate them. The tools at our disposal are intense laser pulses of short duration, and the systems we study are atoms. A host of exotic phenomena may occur in strong-field light–matter interaction, such as high-order harmonic generation and above-threshold ionization. These processes exhibit aspects of both quantum mechanics and classical mechanics, in a fascinating blend.An important part of the work described in this thesis concerns the quantum paths of the electrons involved in these processes. The link between their journey and the time at which their journey begins is examined in a variety of ways. One property that quantum mechanical particles do not share with their classical counterparts is that the former may take a multitude of paths to reach their final destination. Furthermore, these paths may interfere such that the probability of detecting the particle is enhanced, suppressed, or sometimes even completely cancelled out.