| The strong coupling effect between cavity modes and excitons in various semiconductor optical microcavities has been extensively studied in many fields.As a typical wide bandgap direct bandgap material,II-VI semiconductor materials have a specific morphology,and have a very large exciton binding energy and strong exciton oscillator strength,which provides a favorable method for studying light-matter coupling platform.it is also found that the nanostructure materials have extremely limited adjustment methods for the coupling effect,which greatly hinders the progress of this research field,but in practical applications,it is very necessary to achieve dynamic controllability,and subsequently proposed "strain engineering " This method has low equipment requirements and a large adjustment band gap area,which promotes the application prospects.In this work,ZnO micro/nano materials will be used as the experimental sample,and conduct the experimental characterization of the dispersion,the dependence of power and lasing of the cavity polariton in ZnO microwire under stress regulation by means of the spectral method with sub-micron spatial resolution.The main research contents of this article are as follows:First of all,it is proposed to dynamically modulate the exciton polariton the ZnO whispering gallery microcavity through strain engineering.By using home-made strain apparatus,a nearly uniaxial stress is precisely applied to ZnO microwire and thus induces an internal strain along its c-axis.This method is simple,accurate and stable.Using angle-resolved micro-photoluminescence spectroscopy to clearly characterize the dynamic tuning of cavity polariton modes.It is clear from the experimental results that the similar repulsion behavior caused by the coupling of cavity mode and exciton in ZnO microwires.Moreover,the coupled oscillator's model with fitting parameters of strain-dependent excitons' energies can well describe the modes' red-shift,the dispersion relationship between cavity mode and exciton is calculated,which can commendably describe the red shift of microcavity mode.In order to further understand the effect of elastic strain on the cavity polariton modes,a micro-area fluorescence spectroscopy system built by ourselves was used to study the microcavity mode movement of ZnO microwires under strain regulation.Moreover,in the near band-edge region,it shows that the modes' red-shift can be also understood by strain-induced the refractive index increasing,described by Lorentz model,of which underlying mechanism is also related to light-exciton strong coupling.This study shows that strainengineered cavity polariton would pave an alternative way to develop polariton-based integrated or flexible optoelectronic devices.Secondly,the lasing behavior of the exciton polariton in a single ZnO microwire at different injection powers is demonstrated.The material is characterized by a fluorescence spectrum using a micro-fluorescence spectroscopy test system.Acquisition of information such as the lasing peak width,intensity and energy of the cavity polariton,so as to quantitatively or qualitatively analyze the lasing and power dependence of micro /nano materials and explore the physical mechanism.In the angular resolution test technology,it is clearly observed experimentally that with the continuous increase of laser power,the proportion of exciton-polariton in the ground state becomes more and more.At this time,a coherent condensed state is exhibited,thereby verifying the appearance of the cavity polarization lasing phenomenon.At last,using a stress stage,the lasing spectra collected from the same sample under different degrees of bending can be obtained,and the behavior of ZnO lasing peak energy movement under different stresses can be observed,this actually opens up new evidence for the survival of the mechanism polariton state above the threshold.These results provide new possibilities for better understanding of the strong coupling of micro / nano structures. |
PDF Full Text Request