Research On Near-field Control Of Surface Plasmons And Their Application

Surface plasmons polaritons(SPPs)is the siginicifiant subject of research in the field of nanophotonics.The SPPs shows excellent capability for the near-field light confinement on the surface of micro-nano metal structures and has the ability to break the diffraction limit,which is an important method to characterize the near-field optics.Due to the flexible adjustment of the amplitude,polarization and phase of the light,SPPs based on all-optical manipulation has flexible near-field distribution information,which promotes the development of near-field optics in Raman enhancement,light manipulation,super-resolution imaging and optical information storage.This thesis focuses on all-optical manipulation of the near-field of SPPs:the tightly focused radially polarized light induces the excitation of virtual probe for Raman enhancement;the tightly focused circularly polarized light induces the generation of electric field-type optical skyrmions for optical manipulation of chiral and achiral nanoparticles;the thogonal dipole light sources induce directional emission of SPPs for the investigation of optical lateral forces.Firstly,we investigated the tip-Raman scattering enhancement based on surface plasmon virtual probes.Here,the virtual probe is a focused surface plasmon field excited by tightly focused radially polarized light.On the basis of generation of the virtual probe,we studied the local electric field enhancement effect of the coupling structure between the virtual probe and the metal probe.On the basis of generating high Raman enhancement factors,the experimental performance of the virtual-real probe coupling structure was investigated: the spectral response of the virtual-real probe coupling structure under different structural parameters was studied to find the best working wavelength;the spatial resolution of the virtual-real probe coupling structure is used for Raman super-resolution imaging;the thermal effect of the virtual-real probe coupling structure is studied to meet the needs of non-destructive detection of biomolecules;considering that it is difficult to achieve high-precision manipulation of metal probes in practical applications,we study the lateral scan stability of this system.Finally,we summarized some typical Raman-enhanced structures to highlight the superiority of our structure in Ramanenhancement.Secondly,we investigated the generation of optical electric field-type skyrmion in the surface plasmonic field and its spin dynamics.On the one hand,the topological number and electric field vector distribution of optical skyrmions were discussed,and the type of optical skyrmion was analyzed;on the other hand,we characterized the transeverse spin properties of optical skyrmions through spin angular momentum.The transeverse spin provides an additional degree of freedom for light manipulation.On the basis of the existence transeverse spin,we revealed the interaction of lateral spin with chiral or achiral nanoparticles through theoretical numerical calculations of optical forces.Thirdly,we carried out a study based on the lateral optical force induced by the undirectional emission of SPPs.On the one hand,we desigined the unidirectional emission of surface plasmons by constructing an orthogonal dipole light source,and characterized the phenomenon of unidirectional emission with the far-field of surface plasmon coupled emission.Further,the regulation the undirectional emission of SPPs by dipoles with different spin states was analyzed.On the other hand,after completing the control of the undirectional emission of SPPs,we studied the effect of the relationship of dipoles with different spin states on the lateral optical force.Finally,we investigated the effect of the height of the dipole light source on the lateral optical force to reveal the near-field coupling effect of the plasmon.In summary,this thesis realized the near-field manipulation of SPPs with different incident light sources,and explored the different near-field characteristics of SPPs.The research of this thesis will have a good reference meaning for Raman spectroscopy enhancement,superresolution imaging,high-density optical information storage,and optical manipulation,etc.