Study On The Multiple-beam Interference And Near-field Diffraction Of Surface Plasmons

Surface plasmon polarized waves are occuring under the interaction between the free electron in the surface of metal and the incident wave.Although there has been a history of almost more than 100 years on the research on the surface plasmon polarized waves,surface plasmon polarized waves don't show its extraordinary property at early time because of it is limited by technological development at that time.Nowadays,owning to the fast speed development of science and technology,especially in the spect of of micro-electronics,which makes it possible to fabricate electronic components and circuit at micrometer and Nanometer scale.so surface plasmon polarized waves gain new attention by researchers.Surface plasmons have three typical features :short wavelength,near field enhancement and localized.Based on the software FDTD Solutions,this thesis discusses the fringes and dot matrix pattern which are generated by multi surface plasmons interferencing,and the diffraction phenomenon of surface plasmons on the surface of metal.In the study of the interference of multi surface plasmons,we use the metal grating coupler to excite SPPs.In the central region where multi beam SPPSencounting,there will be fringes or dot patterns.Owning to the formation of the interference field containing super-diffraction-limited spatial frequency components,we can use this patterns as the microscope excitation field.once this excitation field is translatable experimentally,the high frequency information of objects can be extracted from a set of diffraction-limited images where the excitation fields contain different displacement vectors,which can break the diffraction limit and achieve super-resolution imaging.This part will study that how the interference patterns are varied with the metal grating structure parameters,material and the wavelength of the incident light,source type and so on,so that we can find out the best grating structure and source which can generate the interfence patterns.Then,we study the near field diffraction phenomenon on the Ag film surface.Due to its character of evanescent field,SPs has three typical features: short wavelength,localization and near field enhancement,which are different from the spatial light.But in the near field area,SPs has similar properties in the near field diffraction with spatial light.This part study the diffraction phenomenon in near field of visible source at the range of 400-700 nm.The diffraction phenomenon in near field is limited by the period of gratings,duty ratio and source.when the diffraction grating period is about 3/2 times of the wavelength of the excited SP waves,the effect of the near field diffraction is the most obvious,then the diffraction grating can act as the function of the separation spectrum.