The Study Of Optical Force And Optical Tweezers Based On Surface Plasmon Polaritons

The surface plasmon is the electromagnetic wave propagating on the surface of the metal which can break through the diffraction limit and have a huge local field enhancement effect.With the strong coupling characteristics and the superior properties of the surface plasmon,the dual waveguide structure greatly enhances the optical forces exerted on the nanoparticles in the gap region.Graphene is a new type of photoelectric material rising in recent years,which plays an important role in many fields.The novel grapheme-fiber structure based on graphene and surface plasmons increases the optical force for several orders of magnitude compared with the traditional model of optical tweezers.In this paper,the dual waveguide structure and the grapheme-fiber structure are studied in many aspects,which is of great significance for the further development of optical tweezers.The first chapter describes the background and significance of the research,and introduces the formula derivation,excitation and application of surface plasmon polaritons,the properties of graphene,the classification and application of optical tweezers.The second chapter introduces the relevant optical parameters of graphene,the calculation of the optical force exerted on some medium particles and the brief introduction as well as the usage method of the numerical simulation software(COMSOL).In the third chapter,the mode and optical force of the silver nanowires are introduced,and two new type of surface plasmon waveguide structures are proposed.Through the finite element analysis software,we make the simulation of the mode,the calculation of the mode area,the propagation length and the optical gradient force for the waveguide structure.These two novel waveguide structures can both form deep subwavelength optical energy binding in the nanoscale gap region.Due to the strong coupling between the waveguides and the superior properties of surface plasmon polaritons,the optical gradient force of dual silver nanowire waveguide structure can reach more than 4000fN/W,while the hybrid waveguide structure's optical gradient force is 1000fN/W with a good propagation length.By adjusting the parameters,the nanoscale optical tweezers with adjustable precision can be formed,which can be applied to different scenes to realize the operation for the nanometer particles.In the fourth chapter,two types of graphene plasma waveguide structures are proposed,one is grapheme-fiber,and the other is grapheme-fiber with partially covered.By simulating the relevant parameters through the finite element analysis software,we found that based on the excellent properties of graphene and surface plasmon polaritons,it is far better than the precious metals in the local field enhancement,which can make a huge optical gradient force up to 107fN/W.The grapheme-fiber with partially covered has a better optical gradient force than grapheme-fiber modes and it is more economical in material usage,while the manufacturing process is more difficult.In the above two kinds of cases,the optical force can be doubled by adding a substrate.Above all,these two kinds of structures increase the magnitude of optical gradient force by more than one order compared with traditional optical tweezers,which greatly improves the intensity for capturing the particles,and makes a broad application prospect in the field of high precision capture.The fifth chapter makes a summary of the work for the whole article,and makes a prospect for the development and application of the optical tweezers in the future.