Study About The Transmission Of Surface Plasmon Polaritons Controlled By Nanostructures

With the unique properties and flexible manipulation,surface plasmon polaritons have attracted wide attention in many fields including physics and many scientific fields such as chemistry,biomolecular science,and acoustics.In recent years,the exquisite design and physical characterization of metal structures on the nanometer scale have expanded the researches of surface plasmon polaritons.The control of the excitation and transmission of surface plasmon polaritons,the artificial interference of the interaction between surface plasmon polaritons and nanostructures,the exploration of the new optical phenomena,the design of surface plasmon polaritons optical elements and the studies about the surface integrated optics,super-resolution imaging,optical micromanipulation and high-sensitivity spectrum have become new technologies and hotpots research in the micro-optics and photonics.Surface plasmon polaritons can be excited by metal nanostructures and transmit along the nanostructure interface in the form of evanescent waves.Adjusting the metal nanostructure can artificially change the intensity and phase of the excited surface plasmon polaritons and control the transmission direction of the surface plasmon polaritons so as to realize the deflection and focusing of the surface plasmon polaritons and the generation of the surface plasmonic vortex.This light field regulation behavior in nanometer scale provides a strong technique which supports for the design of planar photonic devices,the construction of surface optical waveguides and planar optical interconnections and the realization of integrated photonic circuits.Based on the excitation of surface plasmon polaritons by metal nanoholes and metal nanoslits,this thesis advances the study about the controllable focusing and surface plasmonic vortex of surface plasmon polaritons.The innovations of this thesis include the following three aspects.The first one is about the design of polarization-controllable multifocal surface plasmonic lenses by using metal nanoholes and the proposed plasmonic lenses can realize spatialmultiplexing and polarization-controllable focusing functions of the surface plasmon polaritons.The second one is about the study of the surface plasmonic vortices using metal spiral nanoslits.A model of ? spiral is proposed to generate the surface plasmonic vortex and the effectiveness of different spirals in surface plasmonic vortices generation is provided.The third one is about the study of the higher order plasmonic vortices based on metal spirals.The modified spiral is proposed and the ideal higher order plasmonic vortices can be generated through adjusting the separation of spiral trajectory.The study of this thesis will play an important role to expand the practical application of surface plasmon polaritons.The specific content of the thesis is arranged as follows.The first chapter is the introduction of the thesis.This chapter mainly introduces the theoretical basis of the thesis.First,the research background of surface plasmon polaritons is introduced.The dispersion relationship and mathematical expressions of surface plasmon polaritons are summarized.The excitation methods of Surface plasmon polaritons including prism coupling and grating coupling are introduced.The advantage of metasurfaces in surface plasmon excitation is obvious.Second,multipoint focusing and directional focusing of surface plasmon polaritons controlled by nanoholes and nanoslits are introduced.Next,optical vortices and their significance are explained.The common methods to generate optical vortices including computational holography,spiral phase plates,and spatial light modulators,and so on,are introduced.The comparison shows the convenience of the spiral structure in surface plasmonic vortex generation.The second chapter of the thesis introduces two kinds of surface plasmonic lenses.We use nanohole as the basic structure and utilize two different methods to design two kinds of surface plasmonic lenses to achieve the directional controllable focusing of surface plasmon polaritons.Two methods are transmission phase compensation and geometric phase compensation.Four groups of linearly arranged nanohole arrays are used to make up the surface plasmonic lens.The first kind of linearly arranged nanohole arrays have different separations,and the second kind of linearly arranged nanohole arrays have the same separation but different rotation angles.Two phase compensation ways make the surface plasmon polaritons focus and the focusing effect of two surface plasmonic lenses show different polarization dependence.Thereby,the focusing effect with multiple foci and controllable polarization is realized.Theoretical analysis,simulation and experiment results verify the optical performance of surface plasmon lenses.In addition,we further optimize the parameters of surface plasmon lenses to obtain the focusing of the surface plasmon polaritons with high intensity.Our proposed surface plasmonic lenses can be used for polarization detectors and metasurface directional switches and may be applied in integrated optical paths and optical micromanipulation because of tightly focused characteristic of surface plasmonic lenses.The third chapter introduces ? spiral and the generated higher-order surface plasmonic vortices.In view of the wide applications of traditional spirals such as Archimedes spirals,Fermat spirals and exponential spirals in the generation of optical vortices and the current status about the limitation to only generate low order optical vortices,we propose ? spiral nanostructures and explore the generation of optical vortices.Traditional spirals such as Archimedes spirals and Fermat spirals can be taken as special cases of ? spiral.The study shows that for the surface vortices excited by spirals with different ? values,the larger the spiral gap is,the severer the damage of vortex is.A large number of simulation experiments show that the effective range of the order of ? spiral for generating the ideal vortex exists and the metal material also influence this effective range.Our study reveals the physical origin of the distortion among higher-order vortices generated by using traditional spirals,provides the effective range of the order of ? spiral in the ideal vortex generation,and breaks the limitation of the spiral structure in generating high-order plasmonic vortices.The advancement of ? spiral with simple structure will be helpful for generating higher-order vortices and expanding their wide applications.The fourth chapter introduces the study of high-order surface vortices generated by modified spirals.By analyzing the physical origin of the distortion of the high-order surface vortices generated by the metal spirals,a spiral structure with a modified trajectory is proposed and high-order plasmonic vortices with high quality are generated.This study shows that the adjustment of the spiral gap can flexibly control the topological charge of the plasmonic vortex.Practical experiment verifies the effectiveness of our proposed method.The generation of high order plasmonic vortices and the flexible control of topological charge are benefit to expanding the application of surface plasmon vortices in high density information coding,integrated optical communication and optical sensing.The fifth chapter is the summary of this thesis.This chapter summarizes the main content and the innovations of the thesis.At the meanwhile,the shortcomings of the thesis are provided and the following work plan is also discussed.In the following work,the related contents will be improved.