A predicted "Faraday oscillation" in photoexcited semiconductors

TL;DR

This paper predicts a novel Faraday oscillation effect in photoexcited semiconductors when pumped with linearly polarized light, involving a transition from Faraday rotation to oscillation due to exciton-photon coherence.

Contribution

It introduces the concept of Faraday oscillation in semiconductors under linearly polarized pumping, expanding understanding of light-matter interactions in these systems.

Findings

Prediction of Faraday oscillation effect

Dependence on pump and probe polarization orientations

Explanation via many-body exciton-photon coherence

Abstract

While, for semiconductors photoexcited by a circularly polarized pump, the polarization plane of a linearly polarized probe has been shown to rotate, we here predict a spectacular change when the pump beam is linearly polarized, from Faraday rotation to Faraday oscillation, the oscillation of the polarization plane going along a change of the photon polarization from linear to elliptical. This effect, which reduces to zero when the probe field is parallel or perpendicular to the pump field, comes from coherence between the real excitons created by the pump and the virtual exciton coupled to the unabsorbed probe, as easy to see from the Shiva diagrams which represent the many-body physics taking place in this coupled photon-composite-exciton system.