Attosecond control of solid-state high harmonic generation using {\omega}-3{\omega} fields

TL;DR

This study demonstrates attosecond precision control of high harmonic generation in solids by shaping the waveform of mid-infrared laser fields using a fundamental and its third harmonic, revealing the link between electron tunneling and harmonic emission.

Contribution

It introduces a novel experimental scheme to control and monitor high harmonic generation in solids using combined  fields, showing phase-dependent modulation of emission delays and electron populations.

Findings

Maximum harmonic yield occurs at a  phase shift of about /2.

Emission delays of high harmonic photons can reach hundreds of attoseconds.

The phase shift correlates with electron tunneling timing and electric field ratios.

Abstract

High harmonic spectra generated in condensed matter carry the fingerprints of sub-cycle electronic motion and the energy structure of the studied system. Here we show that tailoring the waveform of mid-infrared driving light by using a coherent combination with its third harmonic frequency allows to control the time of electron tunneling to the conduction band within each half-cycle of the fundamental wave with attosecond precision. We introduce an experimental scheme in which we simultaneously monitor the modulation of amplitude and emission delays of high harmonic radiation and the excited electron population generated in crystalline silicon as a function of the relative phase between the $\omega$-3$\omega$ fields. We observe that the mutual $\omega$-3$\omega$ phase required for the maximum yield of high harmonic generation is shifted by approximately $\pi/2$ with respect to the phase leading to maximal generated carrier population. The observed emission delays of high harmonic photons of up to few hundred attoseconds scale with the time delay and with the ratio between the electric field amplitudes of the two-color fields. These results reveal the connection between electron tunneling and high harmonic emission processes in solids.