Research On Strong Light-exciton Coupling And Strain Control In Micro-nano Materials

Micro-nanomaterials have gained a great deal of research in many fields due to their good optoelectronic properties,such as nanometer light source,detector,biomedicine and so on.In this dissertation,the optical-material coupling characteristics and optical properties modulated by Strain-Engineering of semiconductor micro/nano materials are studied,including the fluorescence and kinetic behaviors of exciton polaritons in ZnO tetrapod,optical waveguide properties of strain CdS and the light-exciton-state coupling in MoS₂ and WSe₂ layered materials The main contents of the dissertation are as follows:1.The radius of ZnO tetrapod is adjustable continuously,which provides favorable conditions for the study of exciton-polariton in ZnO whispering gallery microcavities.First,the relationship between the scan position and the radius of the ZnO tetrapod is obtained by using an electron scanning microscope,which is conducive to the quantitative analysis of the experimental data.After that,we used the micro-area fluorescence spectroscopy system designed and built by ourselves to scan along one arms to obtain the radius-modulated spectra and make theoretical fitting.To better explore the exciton polariton kinetics,we measured the fluorescence lifetime at different positions using a one-photon time-resolved test system.Finally,we get the lifetime of ZnO tetrapod exciton polaritons is mainly determined by the radiation decay process,and the radiation lifetime decreases linearly with the increase of sample surface-to-volume ratio.2.We mechanically exfoliated the molybdenum disulfide and tungsten diselenide to obtain a certain thickness of the nanosheet,thereby obtaining the self-configuring Fabry-Perot cavity.The difference between excitations and self-configuration Fabry-Perot cavities in two kinds of materials is studied by the micro-area reflectance spectroscopy system designed by ourselves.Then we use the Coupled Oscillator Model to fit the dispersion relation between microcavity mode and exciton.Finally we get the Rabi split value and oscillator strength of the exciton.This provides a good platform for further study of layered materials.3.Optical waveguides under subwavelength scale have great application prospects,such as for on-chip photonics to link various optical elements or to realize logical operations.We investigate the optical waveguide propagation loss of strain-controlled CdS buckled nanowires at room temperature.In order to get periodically curved CdS nanowires,we first propose a method to prepare buckled nanowires.This method is simple and effective,at the same time,the buckled nanowires are relatively stable.In order to clearly understand the influence of waveguide propagation loss in traveling distance and local strain-induced bandgap shift,we also measured the optical waveguide loss on traight nanowires without strain effect and on buckled NW with fixed traveling distance.Our results indicate that strain-modulated semiconductor nanowires would pave new way to develop multifunctional optical elements and interconnects for integrated and flexible nanophotonic devices.