Optical harmonic generation on the exciton-polariton in ZnSe

TL;DR

This paper investigates optical harmonic generation on exciton-polaritons in ZnSe, revealing intense resonances and symmetry-based insights into the underlying exciton states through experimental and theoretical analysis.

Contribution

It presents a detailed experimental and theoretical study of harmonic generation on exciton-polaritons in ZnSe, including resonance shifts and symmetry analysis, which is novel in this context.

Findings

Resonant harmonic generation spectra show narrow exciton resonances.

Resonance energies are shifted by 3.2 meV from linear reflectivity.

Symmetry analysis elucidates the origin of harmonic signals.

Abstract

We study optical harmonic generation on the 1S exciton-polariton in the semiconductor ZnSe. Intense and spectrally narrow exciton resonances are found in optical second (SHG), third (THG), and fourth (FHG) harmonic generation spectra. The resonances are shifted to higher energy by 3.2 meV from the exciton energy in the linear reflectivity spectrum. Additional resonances are observed in the THG and FHG spectra and assigned to combinations of incident and backscattered photons in the crystal. Rotational anisotropy diagrams are measured and further information on the origin of the optical harmonic generation and the involved exciton states is obtained by a symmetry analysis using group theory in combination with a microscopic consideration.