Theoretical Research And Device Design Of Surface Plasmons Polaritons In Micro-nano Structure

Multi dimensional optical modulation can greatly promote the application of op-tics in various fields of Science.However,due to the dispersion characteristics of the common optical materials,the conventional optical modulator usually has a series of disadvantages,such as large volume,limited range of adjustment and large damage.With the increasing demand for the integration of modern optics,it is important to find new optical modulation materials which can overcome the traditional limitations.Because of the strong local capability of electromagnetic wave in the subwavelength dimension,surface plasmon polaritons provide a theoretical basis for the design of efficient and integrated optical devices.In view of these,the theoretical mechanism and the influencing factors of SPPs excitation in subwavelength waveguides and me-ta-surfaces were systematically investigated in this work,and the corresponding de-signs of optical devices were completed.The main contents of this article are as fol-lows:?1?The Electromagnetically induced transparency?PIT?effect in two-dimensional metal waveguide with double coupling resonator has been researched,and the ultrasensitive photosensitive sensor was desigened on basis of this PIT re-sonance.The waveguide structure consists of a waveguide channel connected with a3/4 circular ring air resonator and a longer air slot resonator.We calculated and ana-lyzed the coupling characteristics of the two resonant cavities with the propagating SP in the waveguide.The 3/4 circular air cavity can be regarded as the bright plasmonic mode since it is directly excited by the waveguide mode,while the air groove cavity can not be directly excited to waveguide mode as dark plasmon mode.The coupling shade patterns between of them generated PIT effect.At the same time,because our designed resonator can support multi resonance modes,three transparent windows are realized in visible and near infrared band.Based on the three level resonance model and numerical calculations,we systematically analyze the coupling characteristics and the energy transfer characteristics of the modes of the induced transparencies.Finally,by changing the effective refractive index of the cavity in the two-dimensional wa-veguide,the modulation effect on the transparent window is studied,and and an ul-trasensitive photosensitive sensor was desigened in visible and near infrared band.?2?The plasmon induced transparency?PIT?in isolated cruciform graphene meta-surface has been researched,and the dynamically tunable optical switche was designed on basis of this PIT effect.The structural unit of meta-surface was placed on the dielectric substrate with three graphene ribbons with same size,one of which was located in the vertical direction and the other two in the horizontal direction.The graphene ribbon in the horizontal direction can be directly excited by the incident light since its polarization direction is in the horizontal direction,and it can be viewed as a horizontal dipole resonance model.Due to the radiation of electromagnetic energy in the near field,the dipole can indirectly stimulate the vertical graphene rib-bons.In this process,the redistribution of electromagnetic energy can induce a re-sonance peak in the transmission spectrum.Based on the three level resonance model and numerical calculations,we systematically analyze the coupling characteristics of this dipole-dipole induced transparency and its energy transfer characteristics.Finally,by using the tunability of the conductivity of graphene,the design of a dynamically tunable mid infrared switch has been completed.?3?Anisotropic transmission properties of double layer L shaped meta-surface has been researched,and the asymmetric transmission?AT?device was designed on basis of this property.This non-symmetric three-layered meta-surface consisted of two equal sized L-shaped silver MMs and a SiO₂ substrate.The monolayer L-shaped metasurface manifests an anisotropic response since its arms are dissimilar.Then,AT for circularly polarized light can be generated.Combining with another monolayer L-shaped meta-surface,we restricted AT for circularly polarized light and pampered AT for linearly polarized light.The calculated results revealed that a narrowband cross-polarization onversion?CPC,90°polarization convertor?can be realized by x linearly polarized electromagnetic illumination and a broadband asymmetric transmission?AT?to for-ward and backward propagate lectromagnetic waves can be acquired from both x and y linearly polarized waves.The effects of the bandwidth characteristics and the chirality of the structure on the resonant characteristics were analyzed in detail.This work pro-vides a choice for the design of asymmetric transmission device.?4?Anisotropic transmission properties of composite meta-surface with 45 de-grees symmetry has been researched,and the 90°polarization convertor and quar-ter-wave plate were designed on basis of this property.This 3D ultrathin design con-sisted of a proposed metasurface?an inner nanocube,an outer ring resonator,and a nanostrip with the symmetrical axis's orientation angle of 45°?,a dielectric substrate,and an ideally conducting silver plane.Combining the transmission line theory and boundary conditions,the anisotropic reflection coefficients are analyzed theoretically.A broad-band and high-efficiency 90°polarization rotator around 1550 nm can be rea-lized with suitable geometric parameters.With similar concept,we also demonstrate a quarter-wave plate with high efficiency and excited bandwidth.The polarization ellip-ticity properties are investigated to further understand the broad-band effect of the proposed polarization convertors.Furthermore,the electric filed distribution indicates that the conversion behaviors are caused by the strong magnetic coupling in the de-signed composite structure.