Optimisation of Quantum Trajectories Driven by Strong-field Waveforms

TL;DR

This paper demonstrates how optimized cycle-shaped laser waveforms can significantly enhance high harmonic generation by controlling electron trajectories at the quantum level, leading to increased XUV flux and spectral cutoff in strong-field physics.

Contribution

The study introduces an experimental method to generate and utilize cycle-shaped waveforms for controlling electron dynamics in HHG, surpassing limitations of traditional sinusoidal fields.

Findings

Two orders of magnitude increase in XUV flux

Enhanced spectral cutoff in high harmonic generation

Controlled electron trajectories at the quantum level

Abstract

Quasi-free field-driven electron trajectories are a key element of strong-field dynamics. Upon recollision with the parent ion, the energy transferred from the field to the electron may be released as attosecond duration XUV emission in the process of high harmonic generation (HHG). The conventional sinusoidal driver fields set limitations on the maximum value of this energy transfer, and it has been predicted that this limit can be significantly exceeded by an appropriately ramped-up cycleshape. Here, we present an experimental realization of such cycle-shaped waveforms and demonstrate control of the HHG process on the single-atom quantum level via attosecond steering of the electron trajectories. With our optimized optical cycles, we boost the field-ionization launching the electron trajectories, increase the subsequent field-to-electron energy transfer, and reduce the trajectory duration. We demonstrate, in realistic experimental conditions, two orders of magnitude enhancement of the generated XUV flux together with an increased spectral cutoff. This application, which is only one example of what can be achieved with cycle-shaped high-field light-waves, has farreaching implications for attosecond spectroscopy and molecular self-probing.