Delay and distortion of slow light pulses by excitons in ZnO

TL;DR

This study investigates how excitons in ZnO influence the delay and distortion of slow light pulses, revealing the role of exciton-polariton resonances and providing detailed excitonic parameters for bulk ZnO.

Contribution

It presents a detailed analysis of exciton-induced pulse distortion and delay in ZnO, including modeling and determination of excitonic parameters with surface and internal discrepancies.

Findings

Pulse delay approaches 1.6 ns at 3.374 eV for 0.3 mm propagation

Bound excitons cause pulse dissection and slowing

Exciton-polariton resonances govern overall delay and attenuation

Abstract

Light pulses propagating through ZnO undergo distortions caused by both bound and free excitons. Numerous lines of bound excitons dissect the pulse and induce slowing of light around them, to the extend dependent on their nature. Exciton-polariton resonances determine the overall pulse delay and attenuation. The delay time of the higher-energy edge of a strongly curved light stripe approaches 1.6 ns at 3.374 eV with a 0.3 mm propagation length. Modelling the data of cw and time-of-flight spectroscopies has enabled us to determine the excitonic parameters, inherent for bulk ZnO. We reveal the restrictions on these parameters induced by the light attenuation, as well as a discrepancy between the parameters characterizing the surface and internal regions of the crystal.