Signatures of Γ1–Γ5 mixed-mode polaritons in polarized reflectance spectra of ZnO

Abstract

Theoretical and experimental studies were carried out on exciton-polaritons excited in ZnO. Polaritons in which both Γ1 and Γ5 excitons couple to electromagnetic waves simultaneously are shown to exist, and their signatures are observed in polarized reflectance spectra measured under k⊥a and E ∥ c configurations for an m-plane sample. Theoretical calculations reveal that the mixed-mode polaritons consist of one Γ1 transverse mode and two Γ5 longitudinal modes. It is also shown that the signatures are sensitive to the valence band ordering.