High-Order Resonant Peaks and Polarization Dependence of Microphotoluminescence in Whispering-Gallery Mode ZnO Microrod Cavity

Jiatian Guo,Xiaobo Yuan,Yunhui Guo,Jingyi Song,Huihui Wei

doi:10.3390/cryst11070824

Abstract

High order phenomena in the visible range and with polarization dependence in the ultraviolet (UV) region of the microphotoluminescence (micro-PL) spectrum in whispering-gallery mode (WGM) ZnO microrod cavity have been thoroughly studied at room temperature. WGM ZnO microrod cavity with good crystallinity is produced by the CVD growth method, and the ZnO microrod structures are characterized by structural and optical methods. Through the micro-PL spectrum measurement of the ZnO microrod, it is found that high-order resonance peaks appeared in the visible region. The different polarization conditions can be adjusted by rotating the angles of the polarizer, and it is proved that the micro-PL spectrum has strong polarization-dependent behavior in the UV region. Our results imply broad application potentials in the study of ZnO microrod-based photonic cavity devices.

Highlights

As an ideal semiconductor material, Zinc oxide (ZnO) has a wide direct band gap and strong exciton binding energy, so the study of its optical properties has aroused great interest [1,2,3,4]
Previous studies reported that the energy difference between the cavity modes and the excitons can be controlled by modulating the radius of the ZnO microrod, so that the energy and the resonance order of the whisper gallery mode (WGM) mode can be tuned [25]
We reported the high order phenomenon in the visible range and the polarization-dependent behavior in the UV region of the micro-PL spectrum in ZnO WGM, which was prepared by chemical vapor deposition method (CVD) method

Summary

Introduction

As an ideal semiconductor material, Zinc oxide (ZnO) has a wide direct band gap and strong exciton binding energy, so the study of its optical properties has aroused great interest [1,2,3,4]. The micro/nanostructure of ZnO can be used as a natural hexagonal whisper gallery mode (WGM) cavity. The ZnO WGM microcavity has become a research hotspot because it has a better laser mode, higher quality factor and lower laser threshold than other microcavities [7,10]. Previous research on the optical properties of WGM microcavities mainly focused on changing the laser pump power density [19,20] or increasing the luminous intensity in the visible region [21] (so high quality factor (Q) and lower lasing threshold optical microcavities can be achieved), and the resonance peaks in the UV region induced by the Rabi splitting have been studied [22,23]. There is still a lack of detailed investigations about the dependence of the resonance peaks on the polarization angle in the UV region

Methods

Results

Conclusion