1. Exciton Polariton Waveguide in ZnO Nanorod
Yanjing Ling, Liaoxin Sun,Hongxing Dong,Zhanghai Chen,,Qijun Ren, Jian Lu,Hui Xiong,, Xuechu Shen
1Surface Physics Laboratory, Department of Physics, Fudan University, Shanghai , China
2Department of Electronic Engineering, East China Normal University, Shanghai , China
An experimental demonstration of exciton polariton guiding in terapod ZnO is studied by micro photoluminescence spectroscopy. A strong coupling of exciton polariton is observed by performing spectral measurement along the arm with a fixed distance between signal detection and the excitation spot. Life-time measurement further supports the polariton waveguide model.
Motivation
Experimental results
The design of optical waveguide has been studied extensively and used in various of applications. However, the wave guide for exciton polaritons has not been reported so far.
The exciton polaritons propagation plays a critical role in understanding the dynamics of exciton polaritons.
Here, we demonstrate, for the first time, a strong exciton-photon coupling in a ZnO WG waveguide.
Spatial-resolved spectra
The physics we are interested in
FIG.4: Spatial-resolved PL mapping along the ZnO tapered arm .
FIG.5: Corresponding waterfall plots of the PL mapping .
FIG.1 : In-plane dispersion of microcavity polariton.
FIG.2: SEM image of the ZnO tetrapod.
A transition from the pure WG optical modes in the weak interaction regime to the excitonic polariton in the strong coupling regime is observed.
Polaritons are quasi-particles originating from strong light and matter coupling in solids. ZnO tetrapod used here has flat and smooth hexagonal resonator facets—whispering gallery (WG) resonator, which allows the strong coupling between WG optical mode and exciton.
The physics of propagation in the two different regime is not the same. In the weak coupling regime, it is photon waveguide, while in the strong coupling, it is exciton polariton waveguide.
Experiment setup
Time-resolved spectra
FIG.6: lifetime measurement of polariton pL at the energy of 3.201eV .
FIG.7: Fit data of Decay time..Inset: PL of polariton.
FIG.3: Confocal micro-photoluminescence system.
Conclusion
we have reported an experimental demonstration of exciton polariton guiding phenomena in tetrapod ZnO, giving a comprehensive picture of the spectra evolution when the emission propagation along the arm of ZnO nanostructure. Tetrapod ZnO, one dimensional structure with unique optical properties, acts as an excellent candidate to investigate the wave guiding behavior .