Control Of Exciton-polariton Properties By Stacked Fabry-perot Microcavity Structures

Fabry-Pérot(F-P)micro resonant cavity is one of the most important basic devices in optical systems.Resonant cavities can generate discrete energy spectra,absorbing light of specific frequency,and amplify light fields.As a result,resonators have been widely used in optical communication devices,sensors,lasers,nonlinear optics,cavity quantum electrodynamics,cavity-optomechanical and many other fields.When semiconductors are placed inside an F-P cavity,owing to the small cavity modal volume,the light intensity or energy density in the cavity can be greatly amplified,therefore,the interaction between photons and semiconductor excitons is enhanced.If the energy interaction exceeds the dissipation of the cavity and excitons,the system enters the strong coupling regime,which leads to the formation of half-exciton half-photon mixed quasi-particles,namely exciton-polaritons.Exciton-polaritons inherit the properties from both the excitons and photons,have wide applications in the fields of quantum physics and optical materials and devices.Modification of exciton-polariton modes can change many important characteristics of these quasi-particles,such as effective mass and interactions.Different materials and geometric parameters of cavities have been applied to change the exciton-polariton modes.However,once a Fabry-Perot microcavity is fabricated,its structure is fixed,so is the optical properties.Focusing on the control of exciton-polariton modes,a stacked double F-P cavities structure is proposed in this thesis.An additional cavity was attached to a prepared cavity containing organic semiconductor molecules.Exciton-polaritons are modified via the coupling between cavity modes.Using the methods of Magnetron Sputtering and spin coating,three layered "Ag-Polymer doped with organic molecules-Ag single cavities and Five layered“Ag-Polymer doped with organic molecules-Ag-Polymer-Ag” double cavities have been prepared.The transmission/reflection/absorption spectra have been obtained with home-made angle resolved spectrum systems.It is shown in the experimental results that the introduction of additional cavity leads to dramatic change of exciton-polariton modes.Three exciton-polariton modes are generated in the stacked double cavities structure.The positions and relative heights of transmission peaks are effectively altered with the optical length of the additional cavity.The strong coupling regime and the double cavities model are verified by the experimental k-E(in-plane wave vector-energy)dispersions and the numerical simulations of transfer matrix method(TMM).In this thesis,control of exciton-polariton modes is realized by the optical coupling between cavity modes without damaging the already prepared cavity structure.Such a method provides new possibilities of related research of exciton-polaritons.Meanwhile,the procedure of sample preparation,characterization,and analyzation used in this thesis may facilitate the development of semiconductor materials and devices.