Interference Of Surface Plasmon Polaritons And Photonic Integrated Devices

Photons are effective carriers for transferring,processing and storing of informa-tion.As an important branch of photonics information technology,micro-nano pho-tonics have been rapidly developed in recent years.Surface plasmon polaritons(SPPs)inspire new methods for micro-nano on-chip integration because of the excellent con-finement and subwavelength properties,arresting many researchers' attentions.In this thesis,we studied near-field interference of SPPs,and found the mechanism of com-posite interference,by which designs of switches and logical gates were established.Cascading synchronous and anti-synchronous interferences together,function of insen-sitive XOR logical gate was finally demonstrated.Moreover,we designed a graphene plasmonic modulator based on groove-structured metasurface with higher modulation depth,broadband response and acceptable insertion loss.The main contents are as follows:1.We studied the interference of SPPs in metallic strip waveguide and found a composite interference contributed by synchronous and anti-synchronous interfer-ences,which is closely related to the width of the stripe waveguide.Utilizing two kinds of interferences,the plasmonic switches and logical gates were obtained.First-ly,we found anti-synchronous interference on flat silver surface,attributed to the transmission-reflection(T-R)interference of two orthogonal SPP waves.Then the metallic strip waveguide was introduced,resulting in a dislocation of anti-synchronous interference curve,and the results even changed to be synchronous owing to the near-field superposition of slit-SPP mode.Therefore,we proposed a theory of composite interference related to the parameters of metallic stripe waveguide.Moreover,a 2 × 2 optical switch within 10?m2 and the functions of logical gates were demonstrated,paving the way for photonic integration of sub-wavelength.2.The synchronous interference in metallic strip waveguide was generalized to the hybrid dielectric-metallic waveguide system,and connected with an anti-synchronous interference,the phase-insensitive result was finally obtained.By introducing an inter-face with two kinds of waveguide system,a design for synchronous interference with a single-pass property was proposed by a controlled mode mismatch leading to different mode conversion.Cascading two kinds of interferences,we theoretically demonstrat-ed a phase-insensitive interference with one of two outputs maintains the destructive interference.Besides,the insensitive port has an output signal with only one input,performing a function of phase-insensitive XOR logical gate.This novel interference effect and process may inspire new ideas for people to build nanophotonic devices.3.A plasmonic graphene modulator was proposed based on groove-structured meta-surfaces,in which a transverse electrical(TE)like mode is accommodated.Our design takes advantage of field enhancement of plasmonic mode,and overcomes the orienta-tions mismatch between electrical field orientations of the surface plasmon polaritons(SPPs)and the graphene plane.Therefore,this graphene based plasmonic modulator exhibits greatly improved modulation depth compared with the conventional SPP ones by three orders based on 2D eigenmode and 3D transmission simulation.Our theo-retical results also show this modulator holds a broadband response with acceptable insertion loss,indicating possible applications in nanophotonic integrations.