Attosecond electromagnetic pulses: generation, measurement, and application. Attosecond metrology and spectroscopy

When intense laser radiation interacts with matter, high-order harmonic generation (HHG) takes place; recent achievements in this area were reported by the authors in a review [V V Strelkov et al. Phys. Usp. 59 425 (2016)]. Under certain conditions, the phases of the harmonics can be synchronized in such a way that, adding up, the fields of the harmonics form attosecond ultraviolet (or X-ray) pulses. In this review, we address the generation of a train of attosecond pulses and a single attosecond pulse from a group of high-order harmonics. The problem of measuring the duration of attosecond pulses required both a serious modernization of the measurement methods known in femtosecond optics and the development of fundamentally new approaches. This review describes the main methods for measuring attosecond pulses that have been successfully demonstrated to date. Finally, the use of such pulses to probe the dynamics of electronic processes in matter and to control such processes at attosecond times is discussed.