Polariton condensation and surface enhanced Raman in spherical ZnO microcrystals

Abstract

Preparation and characterization of polariton Bose–Einstein condensates in micro-cavities of high quality are at the frontier of contemporary solid state physics. Here, we report on three-dimensional polariton condensation and confinement in pseudo-spherical ZnO microcrystals. The boundary of micro-spherical ZnO resembles a stable cavity that enables sufficient coupling of radiation with material response. Exciting under tight focusing at the low frequency side of the bandgap, we detect efficiency and spectral nonlinear dependencies, as well as signatures of spatial delocalization of the excited states which are characteristics of dynamics in polariton droplets. Expansion of the photon component of the condensate boosts the leaky field beyond the boundary of the ZnO microcrystals. Using this, we observe surface polariton field enhanced Raman responses at the interface of ZnO microspheres. The results demonstrate how readily available spherical semiconductor microstructures facilitate engineering of polariton based electronic states and sensing elements for diagnostics at interfaces.

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

“…These results indicate that the intensity changes of the two peaks have a strong dependence on the polarization, and the peak at the 378 nm has the greatest dependence. As mentioned in previous reports, the generation of resonance peaks in the UV region is mainly due to the selective transition rule of A exciton, B exciton and C exciton; A exciton has polarization properties, so the fluorescence intensity of TE polarization is higher than that of TM polarization, and the transition selectivity rule determines that A exciton is a complete TE polarization, B exciton has a certain transition probability under TE and TM polarization, while C exciton is mainly TM polarization [18,19,25,32]. According to the experimental results, the 0 • polarization angle corresponds to the TE polarized light: in this case the light collected by the WGM microcavity is the light of the A and B exciton transitions, which exhibits strong intensity.…”

“…It is found that the typical ZnO luminescence is mainly concentrated on two bands: one is the UV region (shorter than 400 nm), and the other is the visible region (mainly concentrated in region of 500-700 nm) [15,16]. Excellent luminescence properties appear both in the UV region and the visible region; therefore, ZnO has superior prospects for the research of UV or visible photon nanodevices [17,18]. 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 also been studied [22,23].…”

Ultra-responsive and highly sensitive 1D ZnO nanotubes for detecting perilous low levels of NO2 gas

“…Additionally, ZnO shows good electron mobility, inherent sensing capabilities, and robust electrical properties and offers the most diverse range of nanostructures. [35][36][37][38][39][40][41] Furthermore, it has drawn the attention of many researchers due to its excellent ability to detect NO 2 gas. A comparison of NO 2 responses of ZnO-based sensors with those of other materials demonstrates that ZnO-based sensors are capable of detecting NO 2 gas, as shown in Table 1.…”