Versatile Sources of High-order Harmonics for Multiple Applications

High-order harmonic generation (HHG) in gases and its applications is today an active field of research worldwide. High-order harmonics are created when intense laser radiation interacts with a gas of atoms or molecules. In the time domain, the emission is a train of pulses in the extreme ultraviolet range, separated by half a laser cycle and with attosecond duration. The interference between attosecond pulses results in a frequency comb of high-order (odd) harmonics. This tutorial will introduce the physics of high-order harmonic generation and attosecond pulses.