Research On The Strong Coupling Of Two-dimensional Perovskites In Optical Fabry-perot Microcavity

The Fabry-Perot cavity(F-P)microcavity is a precision optical system.Its internal volume is so small that it can form a cavity mirror structure,which can confine the light field and regenerate the photonic state in the microcavity.After the semiconductor material is embedded in the microcavity,excitons are excited by excitation light,and the coupling effect of excitons and photons is generated in the cavity.Considering that the coupling strength in the microcavity is closely related to the optical properties of the embedded material,choosing a suitable embedding layer can optimize the spatial structure of the cavity and improve the coupling strength,which is conducive to further research on strong coupling.The coupling strength is sensitive to the halogen composition,so quasi-2D perovskite is chosen as the intercalation material.Unlike 3D materials,stronger coupling can be created within the microcavity.In addition,most semiconductor materials generally have the coupling effect of internal excitons and external photons at low temperature,while perovskite materials can show relatively obvious exciton-photon coupling at room temperature,so we choose perovskite.It is a good object to study the strong coupling mechanism at room temperature.This paper aims to study the strong coupling effect inside the F-P microcavity after embedding a 2D perovskite layer.When strong coupling occurs,the coupling strength of excitons to the optical field is greater than the relaxation rate.At this time,Rabi oscillation occurs between the ground state and the excited state of the atom,which is manifested as Rabi splitting of coupling peaks in the ultrafast time spectrum.Split,and form half-light half-matter state exciton polarons(Exciton-Polaritons).Based on this,this project intends to build a femtosecond pumping system to detect steady-state spectroscopy,transient spectroscopy and coherent dynamics inside two-dimensional perovskite and F-P microcavity composites.The main contents of the research are as follows:1.Firstly,the problems existing in the development of the optical microcavity are discussed,and the structural characteristics of the optical microcavity system and the generation principle of the strong coupling effect in the cavity are summarized.At the same time,the exciton effect and the generation mechanism of polaron are introduced.Next,this paper discusses the structural characteristics and optical properties of intercalated media,namely perovskite materials,and the application advantages of 2D perovskite materials.Then,the principle of the femtosecond pump detection technique used in this paper is introduced,and the structural characteristics and optical properties of the two-dimensional perovskite-F-P microcavity composites are analyzed.2.The optical microcavity structure designed in this project is made of glass as the substrate,and the silver material is evaporated as the mirror structure of the F-P microcavity,it is a five-layer structure.A pure phase quasi-2D perovskite(PEA)₂(MA)Pb₂I₇layer was located in third layer.Two spin-coated PMMA layers were used to separate the perovskite and silver mirror,in order to aviod emission queching.By adjuting the parameters of the optical microcavity,we get very robust optical microcavity and quasi-2D perovskite strutcture.3.The basic optical properties of the composite of two-dimensional perovskite and optical microcavity are characterized by steady-state reflection and fluorescence spectroscopy.The results of perovskite on the silver plane are compared to prove the occurrence of strong coupling.The coupling results show that the high-energy and low-energy exciton polaritons of half photons and half excitons satisfy the inverse cross-dispersion relationship,which further proves the authenticity of the strong coupling,and the Rabi splitting reaches 142me V.4.The transient spectroscopy and hybrid exciton dynamics of two-dimensional perovskite-optical microcavity complexes are studied by ultrafast spectroscopy.The comparison of transient spectra of 2D perovskite in the F-P microcavity and on the silver plane shows that the ground-state bleaching peak is clearly split,which corresponds exactly to the steady-state result.On the other hand,the exciton polaritons of half photons and half excitons inherit the spin-polarized properties of pure perovskite excitons and follow the optical selection rule of circular polarization.Meanwhile,in the microcavity,the dynamic spin polarization and relaxation time of excitons are shorter than those of pure perovskite,proving that the cavity can also enhance the interaction between excitons.