The interplay between high-harmonic generation and photoluminescence in ZnO: Anisotropic spectral properties of harmonic emission and the role of excitons

TL;DR

This study explores the complex interaction between high-harmonic generation and photoluminescence in ZnO, revealing how intense infrared excitation influences their spectral properties and underlying mechanisms.

Contribution

It uncovers the spectral and intensity-dependent behaviors of HHG and PL in ZnO, highlighting their roles as probes for strong-field and many-body effects in wide-bandgap semiconductors.

Findings

HHG exhibits non-perturbative scaling and spectral blueshift.

PL shows superlinear increase and redshift due to exciton interactions.

Transition in fifth harmonic generation mechanism with intensity.

Abstract

We investigate the nonlinear optical response of bulk ZnO under intense short-wave infrared excitation, focusing on the interplay between high-harmonic generation (HHG) and photoluminescence (PL). While HHG exhibits non-perturbative intensity scaling and a spectral blueshift consistent with plasma-induced refractive index changes, the PL signal shows a pronounced superlinear increase and a redshift, attributed to a combination of exciton-exciton scattering and phonon-assisted exciton recombination emission. A similar PL response under above-bandgap excitation supports its intrinsic origin. Spectral analysis of the HHG emission reveals an intensity-driven transition in the characteristics of the fifth harmonic, indicating a change in the underlying generation mechanism. These findings establish PL and spectral HHG analysis as complementary probes of strong-field and many-body effects in wide-bandgap semiconductors.