Controlling Spectra Of Exciton-polaritons With The Near-field Optical Distribution Of Surface Plasmon Polaritons

In recent years,strong coupling phenomena between light and matter have attracted great attention as the rapid development of the field of nano optics.Hybridized state of photon and semiconductor exciton has become one of the most important topics in many fields such as quantum optics and nano photonics.Surface plasmon polariton(SPP)based on metal films can exchange energy with semiconductor excitons inside its mode.Under certain conditions,they enter the strong coupling regime and form half-exciton/half-photon quasi particles,namely Exciton-Polariton(EP).EP based on SPP has properties of both excitons and photons,and has potential applications in the fields such as lasing without inversion,photovoltaic materials and devices,nonlinear optics,and quantum information.In order to advance the application of EP in these fields,the basic properties and related factors need to be studied,such as the control of Rabi splitting and spectral dispersion.SPP can be viewed as the collective oscillations of free electrons at a metal surface.Its properties are affected by factors such as material,thickness,and environmental refractive index.Therefore,the optical characteristics of SPP can be controlled by the structure and optical parameters.Subsequently,the EP properties can be modified accordingly.Focusing on the control of EP based on SPP,the following researches have been carried out:1.The SPP modes of silver nano films were experimentally observed with angle resolved reflection spectra,and the corresponding near-field optical distributions were numerically calculated.A spectroscopy system was designed and constructed based on the Kretschmann configuration.SPP spectra have been investigated for silver films with different thicknesses.It has been experimentally shown that the thickness of silver film has important effects on the depth of resonant dips induced by SPP.As the thickness is increased,the minimum reflection at the resonant dip of SPP increases at first,then decreases.The near-field distribution of optical field was calculated with the Transfer Matrix Method,and the exponential decrease of optical intensity on the direction perpendicular to the silver surface was obtained.For the effective stimulation of SPP modes,the thickness of silver films was optimized to 50 nm.2.The effects of the dielectric films on the near-field optical distribution and EP properties have been studied.When the near-field optical field of SPP was modified by changing the thickness of polymer film dopped with organic molecules,the observed EP spectra change dramatically.The relationships between wavelength of spectral dips and incident angle vary greatly.As the thicknesses of the polymer films increase,the Rabi splitting becomes larger.The modification of EP with thickness of dielectric layer has been analyzed with the aid of numerical results obtained by the Transfer Matrix Method.Because the angle-resonant wavelength relationship is sensitive to the environmental refractive index near the metal film,the angle-resonant wavelength relationship is altered a lot by the thickness of polymer film dopped with organic molecules.Moreover,with the increase of polymer film,more excitons are coupled to one SPP mode.Collective effect of strong coupling induces larger Rabi splittings.When the thickness of polymer film increases from 20 nm to 52 nm,the Rabi splitting grows from 103 me V to 151 me V,which is 1.47 times to the original value.Angle resolved photoluminescence spectra verified the EP properties.In this thesis,the spectral properties and near-field optical distributions of SPP based on silver films are investigated.Based on the obtained results,the control of EP modes with thickness of dielectric layer is demonstrated.The phenomena shown in this thesis have positive effects on the application of EP in optoelectronic materials and devices.