Effects Of Ag Substrate On Photoluminescence Of ZnO Microcavity

In the past two decades, the coupling of excitons and photons in planar microcavities has been studied in both experimental and theoretical research, Weisbuch et al. made the first demonstration of the strong coupling in a semiconductor quantum microcavity. They used a Fabry-Perot (F-P) microcavity made of GaAs quantum wells imbedded between two distributed Bragg reflectors (DBRs). Compared to those planar microcavities, semiconductor microcavities have the advantage of offering both excitons and confined cavity at the same time. Compared to other semiconductor microcavities, wide band-gap ZnO microcavity with binding energy (-60meV) is more popular because it has the possibility to couple excitons with photons in room temperatures, and the coupling is much easier to be observed. Furthermore, the property of the microcavity will be changed when we bring in metal substrate, which may lead in surface plasmon polaritons(SPPs) to break the diffraction limit of the conventional optics so that we can open an area of subwavelength optics.In this study,We compared the photoluminescence(PL) spectra of different parts of the same ZnO microrod with half on the Ag substrate and half impending in the air. Their dispersion curves were than attained from the PL spectra. We bring in a factor Γ to describe the enhancement of the oscillator strength of the exciton-photon interaction. With the appropriate value of Γ, our dispersion curves fitted the theoretical result of the exciton-photon interaction well, which showed strong coupling effects between the F-P modes and the excitons at room temperature. Moreover, we found that enhancement of the oscillator strength of the ZnO microrod on the Ag substrate was 1.96 while that of the ZnO microrod impending in the air was 1.68, which showed the exciton-photon coupling in ZnO microrod on the Ag substrate was obviously enhanced. Meanwhile, we obtained the reflection phase of Ag was-0.77π at 416nm which was similar with the result -0.72π got from the Refractive Index Database.