Research On Pupil And Raman Enhancement Techniques Based On Surface Plasmons

Surface plasmonpolariton(SPP)is an electromagnetic oscillation mode formed by interaction of free electrons at metallic surface with incident photons.It has shown remarkable achievements in various of application,e.g.SPP manipulations,Surface-enhanced Raman scattering(SERS),SPP nano-lithography,and super resolution imaging,etc,due to its specific characteristics in electric field enhancement and confinement.Electromagnetic energy could be highly enhanced and localized between nano structures and metallic surface,by the interaction between SPP and localized surface plasmon(LSP)of the metal nanostructure.The field enhancement leads to a higher gradient force in the SPP field and results in a more stable trap,which is becoming a frontier research.In addition,the nanoscale highly enhanced field provides great potential in small signal enhancement,super-resolution imaging,biosensors,and so on.SERS is a great technique for enhancingRaman spectroscopyby using the electromagnetic field local a nd enhancement capability of metal nanostructures.In this thesis,base on detailed introduction of the SPPbasic principle,a focused all-optical modulated SPP tweezers system is proposed firstly,to overcome the weakness of classical trapping techniques.By employing theSPP optical tweezers,weachieve the in-plane trapping and manipulation of a single ZnO nanowire,and build some typical nanowire structure.Further,enhanced Raman signal is researched based on the SPP field enhancement,theoretical analysis of field confinement and enhancement under different polarizations are implemented,and SERS signal is detected experimentally to reveal the enhancement mechanism of Gap structure.The chief content of this thesis could be divided into the following four aspects:1.Firstly,the background and development of SPP are introduced.Further applications,both plasmonic tweezers and SERS based on Gap structures,are briefly referred combined with the research contents.2.Fundamental theories of SPP and LSP are introduced,reviewed the emergence and development background of SPP.The mechanicalmodel of nanoparticles located in plasmonicfield is analyzed in details.3.Forces acted on the nanowires in the SPP field are calculated theoretically by MST and FDTD methods.Linear polarized laser beam is applied to exc ite SPP to trap and rotate ZnO nanowire,and special plasmonic structures are built the on metal film.4.Based on the plasmonic hybridization of SPP excited by tightly focused beam and LSP of nanoparticles,high electromagnetic field intensity with nanosize are achieved in the gap structure.The enhanced field distributed in the Gap under different polarizations is implemented,and the corresponding SERS signal is detected experimentally.