Study On Transmission Characteristics Of MIM Waveguide Coupling Structure Based On Surface Plasmon Polaritons

In the 21st century,the field of optics has developed sufficiently,but the resolution of traditional optical devices can no longer be improved due to the limitation of diffraction limit,so traditional optical devices can no longer meet the requirements of the current practical application.Surface Plasmon Polaritons(SPPs),a special electromagnetic wave generated on the metal-insulator surface due to the interaction of incident photons and free electrons on metal and propagates on the metal surface.Due to the local enhancement effect of the electromagnetic field,the characteristics of sizes of sub-wavelength and the sensitivity to the changes of the environment have become research hotspots in recent years.Among the structures that control and transmit SPPs,the metal-insulator-metal(MIM)metal waveguide coupling structure has become a key research object in this field because of its simple structure,high integration and high resolution.Fano resonance is a special optical phenomenon based on the SPPs waveguide coupling structure.Its essence is formed by the destructive interference of continuous broadband mode(bright state)and discrete narrowband(dark state).Its output spectrum is ultra-narrow and extremely sharp asymmetric resonance lineshape.Because the output spectrum of Fano resonance is extremely sensitive to changes in the surrounding environment,changes in the small environment will cause larger wavelength shifting.Therefore,the application of the MIM waveguide microstructure based on Fano resonance in the sensing field can greatly improve the sensitivity and provides a better choice for high-precision measurement.In this paper,three MIM waveguide coupling structures based on surface plasmon polaritons are designed and systematically simulated and analyzed by Finite Element Method(FEM).The main contents are as follows:1.A nano metal structure based on the coupling system of a MIM waveguide with a stub and a horizontal B-Type resonance cavity(HBTRC)is designed.The simulation results show that the output spectrum has a sharp Fano resonance curve.The mechanism of Fano resonance is analyzed,and the distribution of the magnetic field of the entire system is discussed by breaking the symmetry of HBTRC.The influence of each parameter of the entire system on the transmission characteristics is discussed in depth.The designed structure has a sensitivity of 1548 nm/refractive index unit(RIU)and a figure of merit(FOM)of 59.2.A compact nano metal structure based SPPs,which is composed of MIM waveguide with a silver bar and a triangular stub and a half ring resonance cavity(HRRC).The finite element method is used to analyze the transmission spectra of the designed structure.The transmission spectrum shows that the system excites a typical Fano resonance lineshape.The reasons for Fano resonance are analyzed from the perspective of the output spectrum of the substructure and the interference effect between each optical path.The influence of the structural parameters on the transmission characteristics is discussed.With the optimal system parameters,the maximum sensitivity of the system is 1723 nm/RIU,and FOM is 51.3.A simple nano metal structure consisting of the bus waveguide with a single stub and a racetrack ring cavity is designed.The spectral characteristics of the proposed structure are analyzed by the finite element method.The results show that there are sharp Fano resonance characteristics and electromagnetically induced transparency(EIT-like)effects,which are excited by the coupling between the MIM waveguide with a single stub and the racetrack ring resonator.The influence of the stub as the coupling point at different positions on Fano resonance is discussed and the influence of geometric parameters on the tansmission performance is discussed,too.It also introduces the fabrication method of the structure and the main instrument for testing the system.When the metal material of the system is Ag,the material loss of the whole structure is discussed.The sensitivity of the proposed structure can reach 1774 nm/RIU,and the FOM is 61,then three applications are discussedThis paper proposes three micro-nano coupling structures based on MIM waveguides.Firstly,analyzing the generation mechanism of Fano resonance,then discussing the magnetic field distribution H_Zof each structure.Finally,the parameters of each structure are optimized to obtain the best transmission characteristics.The work in this paper provides a new option for the application of SPPs-based microsystems to micro-nano integrated optical chips.