Enhanced high-order harmonic generation in donor-doped band-gap materials

TL;DR

This paper demonstrates that donor doping in band-gap materials significantly enhances high-order harmonic generation efficiency by leveraging impurity states, with implications for advanced photonic applications.

Contribution

The study introduces a novel understanding of how donor-doped materials boost HHG efficiency through impurity states, supported by time-dependent density functional theory simulations.

Findings

Donor doping increases HHG efficiency by several orders of magnitude.

Impurity states within the band gap enable a new HHG mechanism.

Harmonic cutoff varies with doping type, explained by semiclassical analysis.

Abstract

We find that a donor-doped band-gap material can enhance the overall high-order harmonic generation (HHG) efficiency by several orders of magnitude, compared with undoped and acceptor-doped materials. This significant enhancement, predicted by time-dependent density functional theory simulations, originates from the highest-occupied impurity state which has an isolated energy located within the band gap. The impurity-state HHG is rationalized by a three-step model, taking into account that the impurity-state electron tunnels into the conduction band and then moves according to its band structure until recombination. In addition to the improvement of the HHG efficiency, the donor-type doping results in a harmonic cutoff different from that in the undoped and acceptor-doped cases, explained by semiclassical analysis for the impurity-state HHG.