Optimal control of high-harmonic generation by intense few-cycle pulses

TL;DR

This paper presents a quantum optimal control method to enhance high-harmonic generation in laser pulses, achieving higher yields and extended cutoff energies crucial for attosecond pulse production.

Contribution

It introduces a computational approach that optimizes driving pulses for high-harmonic generation, combining classical and quantum effects to improve performance.

Findings

Remarkable cutoff extension achieved in a 1D H-atom model

Yield enhancement due to increased tunneling probability

Method applicable to more realistic models and experiments

Abstract

At the core of attosecond science lies the ability to generate laser pulses of sub-femtosecond duration. In tabletop devices the process relies on high-harmonic generation, where a major challenge is to obtain high yields and high cutoff energies required for the generation of attosecond pulses. We develop a computational method that can simultaneously resolve these issues by optimizing the driving pulses using quantum optimal control theory. Our target functional, an integral over the harmonic yield over a desired energy range, leads to a remarkable cutoff extension and yield enhancement for a one-dimensional model H-atom. The physical enhancement process is shown to be twofold: the cutoff extension is of classical origin, whereas the yield enhancement arises from increased tunneling probability. The scheme is directly applicable to more realistic models and, within straightforward refinements, also to experimental verification.