Coherent Polariton Modes and Lasing in ZnO Nano‐ and Microwires

Abstract

This article presents a topical literature survey on types of coherent states in bare and functionalized ZnO nano‐ and microwire microcavities, together with own new approaches of the authors. By optical excitation, coherent emission from electron–hole plasma and from exciton‐polariton Bose–Einstein condensates, both up to room temperature, have been observed by various research groups. The impact of the interplay between the excitation properties and geometry of the structures as well as of the charge carrier dynamics on the emission behavior of the structures has been discussed. For different cavity types spectrally tunable mono‐/dual‐mode laser operation as well as propagation of coherent polariton states have been demonstrated. Further functionalization of the bare structures in hybrid systems allows optimization and engineering of the cavity as well as the polariton mode structure and the design of sophisticated light–matter states.

Determination of Dispersion Relation and Optical Parameters Induced by Exciton–Polariton Effect in Whispering-Gallery Microcavities Using Photoluminescence Spectroscopy

“…This effect can be utilized in the aspect of slow light technique. , We can also indicate the Rabi splitting energy ℏΩ B ∼ 210 meV and ℏω C ∼ 248 meV directly from the E – k diagrams (Figure ). The Rabi splitting energy of our modified model seems smaller than the analytical predictions ( ) of the unmodified Lorentz oscillator model, which are 294 and 317 meV due to the interactions between cavity photons and B, C excitons. In fact, this analytical formula ℏ , derived from the unmodified model, is strongly dependent on the choices of the constant dielectric term ε b .…”

“…) of the unmodified Lorentz oscillator model, 10 which are 294 and 317 meV due to the interactions between cavity photons and B, C excitons. In fact, this…”

“…In the strong coupling regime, cavity photons can couple strongly with light-induced excitons to form exciton–polaritons, which have the properties of bosons. Due to the small polariton effective mass, the Bose–Einstein Condensate (BEC) can be realized at room temperature. − With the polariton condensation, the stimulated polariton recombination process can lead to polariton lasing without the requirement of population inversion. Therefore, it can reduce the power consumption and facilitate the development of all optical integrated devices, such as polariton transistor, polariton router, polariton spin switches, and quantum computing …”

“…ZnO microrods (MRs) grown by chemical vapor deposition (CVD) method possess a typical hexagonal cross section, which reflects the wurtzite crystal structure in nature. The resonant optical modes corresponding to the whispering gallery modes (WGMs) in the hexagonal cross section can be determined by considering the phase matching condition due to the total internal reflection. , Because of the strong light–matter interactions, the refractive index changes significantly and enhanced the absorption when the energy of the cavity mode approaches the exciton resonance energy. , Practically, the upper polariton branch (UPB) is hard to be detected by PL measurements due to the intense absorption of conduction band. Hence, only lower polariton branch (LPB) can be utilized to extract the Rabi splitting energy.…”

“…The resonant optical modes corresponding to the whispering gallery modes (WGMs) in the hexagonal cross section can be determined by considering the phase matching condition due to the total internal reflection. 10,29 Because of the strong light−matter interactions, the refractive index changes significantly and enhanced the absorption when the energy of the cavity mode approaches the exciton resonance energy. 30,31 Practically, the upper polariton branch (UPB) is hard to be detected by PL measurements due to the The success of this concise method can be credit to the morphology of the microcavity due to its crystal structure and the strong oscillator strength in nature.…”