Dynamics of high-harmonic generation in terms of complex Floquet spectral analysis

TL;DR

This paper analyzes high-harmonic generation in a two-level quantum system driven by a laser using complex Floquet spectral analysis, revealing quantum interference effects and phase control of HHG dynamics.

Contribution

It introduces a microscopic Floquet spectral analysis approach to understand HHG, highlighting the role of resonance states and phase control in the process.

Findings

Quantum interference of Floquet resonance states influences HHG regimes

Phase of the laser controls HHG photon emission dynamics

Spectral features resemble those of HHG in solids

Abstract

High-harmonic generation (HHG) of a two-level-system driven by an intense monochromatic phase-locked laser is studied in terms of complex spectral analysis with the Floquet method. In contrast to the phenomenological approaches, this analysis deals with the whole process as a coherent quantum process based on microscopic dynamics. The spectral decomposition corresponding to the contributions of the Floquet resonance and dressed continuous states of the total system have been obtained. The calculated HHG spectrum exhibits the characteristic features of the HHG from solids. We found that the quantum interference of the Floquet resonance states is responsible for the transition from the adiabatic to the stationary regime in the HHG process and that the phase of the driving laser controls the dynamics of the HHG photon emission.