Abstract

Ultrafast optical pulse generation plays important role in pump/probe measurement for the fastest dynamics study in atoms, molecules and materials. Among all of nonlinear effects to generate short pulses, high-order harmonic generation (HHG) opens a path towards the production of the shortest light pulses, with durations in the order of the attosecond time scale. The generation mechanism of HHG is easily understood by the semi-classical three-step model: an electron is ionized and accelerated by an intense driving electrical field; after half-cycle of the driving pulse, the electron is pulled back, re-colliding with the parent ion [1,2]. The kinetic energy accumulated during propagation in the continuum is released as high-energy –or high-frequency– radiation, ranging from the extreme ultraviolet (EUV) to the soft X-rays. Due to the nature of the HHG process, attosecond bursts are emitted every half cycle of the infrared (IR) laser field, resulting in the generation of an attosecond pulse train when multi-cycle driving pulses are used.

© 2019 IEEE