All Fiber Special Beam Generators Based On Surface Plasmon Polaritons

The all-fiber special beam generator based on surface plasmon polaritons was proposed and demonstrated.The gold film was deposited on the end face of the single and multiple core optical fiber.An air slit was carved in the center of each core and the gratings with a fixed period were fabricated on the gold film on one side of the slit,the amplitude and phase of the uncoupled optical field are approximately satisfied with the distribution law of the required beam,the deflected beam and multi-beam interference can be obtained at the end of optical fiber,which can be used as beam shaping devices.This beam generator does not need strict spatial collimation and complex coupling optical path,and has the advantages of high integration,flexible operation,stable system and strong anti-interference.First,the advantages and disadvantages of the traditional optical trapping model and the common beam shaping devices were summarizes,then the characteristics and excitation conditions of surface plasmon polaritons,optical trapping force calculation method and other theoretical knowledge related to the all-fiber beam generator were introduced.Single deflected and symmetrical multiple deflected beams were designed and realized,the mechanical effect of two-core optical fiber symmetrical deflection-beam interference is studied,which lays a foundation for the particle trapping.The main contents are as follows:All fiber beam shaping devices based on surface plasmon polaritons.According to the characteristics and excitation principle of the surface plasmon polaritons,the metal grooves and air slits were designed on the end of the optical fiber,and the beam with fixed deviation angle is obtained.This paper introduced the design and regulation of nanometer slit-groove structure of beam deflection angle method in detail,the structure is integrated on the single-core and multicore optical fiber used FDTD Solutions and Comsol Multiphysics optical simulation software for numerical simulation calculation.The influence of the change of the structure parameters on the all-fiber special beam generator is studied.The numerical simulation results showed that the metal microstructure could adjust the deflection angle of the beam by changing the grating period and realized an accurate and tunable all-fiber beam generator.The results further proveed that this structure can realize all-fiber beam generator with simple and precisely tunable.A multi-deflection beam generator based on multi-core optical fiber.The metal microstructure was integrated on the end face of the multi-core optical fiber.Twin-core and four-core optical fiber special beam generators were fabricated by use of metal structured.Multi-core optical fiber special beam generator emitted multiple deflected beams which will interfere in the overlapping region.The characteristic of the interference field could be regulated by the parameters such as the phase,amplitude and polarization direction of the incoming beam.The trapping characteristics analysis based on all-fiber special beam generator.The characteristics of the overlapping region of two deflected beams generated from symmetrical twin-core fiber beam deflector were studied and applied to the trapping of nanoparticles.Maxwell’s stress tensor method was used to calculate the transverse and longitudinal forces of nanosphere with radius of 50 nm in the interference field,and the effects of the radius of microsphere and the change of incident light conditions on the trapping force of the spheres and the number of trapping points were studied.Calculation results showed that the radius of 50 nm polystyrene spheres could be trapped in a stable point which 49 microns from fiber end,and had multiple trapping locations in transverse direction,it could be realized the nanometer level stable trapping of microspheres with non-contact,long distance and multi-position.