Study On Transmission Characteristics Of Metal-Dielectric-Metal Waveguide Based On Surface Plasmon Polaritions

Surface plasmon polaritons(SPPs)are surface electromagnetic wave that propagate along the metal-dielectric interface and it's amplitude exponentially decaying in the perpendicular direction of the interface.SPPs are considered to have dramatically potential application in the realization of highly integrated optical circuits due to their capability to overcome the diffraction limit of light.This paper mainly studies the transmission characteristics of the following three kinds of metal-insulator-metal(MIM)waveguides based on SPPs:(1)A plasmonic waveguide filter constructed with MIM structure engraved single arc-shaped is firstly proposed.The structure is then extended to symmetrical,asymmetrical and staggered double-sided arc-shaped structure.The results show that the proposed waveguide systems all have the wavelength selection characteristics.For a single arc-shaped waveguide,transmissive valley and transmission peak can be adjusted by changing the central angle,inner radius or width of the arc.Moreover,the opening direction of the arc has no influence on the transmission characteristics.The transmission characteristics can be explained by using resonance conditions,which is consistent with the theoretical results.Compared with a single arc-shaped waveguide,the transmission spectrum of a symmetric double-sided arc-shaped waveguide has a slight blue shift;the spectrum of the asymmetrical double-sided arc-shaped waveguide shows the phenomenon of electromagnetic-induced transparency-like;for staggered double-sided arc-shaped waveguides,the bandgap will increase first and then decrease with increasing staggered length.(2)A plasmonic waveguide system consisting of a tooth-shape and a ring-shape resonator which are coupled to the straight MIM waveguide directly and indirectly,respectively,was studied.By using Coupled-Mode Theory(CMT)and Finite Difference Time-Domain(FDTD)methods,the transmission characteristics of the proposed system are studied.The results show that Plasmon-Induced Transparency(PIT)phenomenon occurs when the resonant frequencies of the tooth-shape and the ring-shape resonator are almost equal to each other.The transmission characteristics,such as the resonance wavelength,transmission peak,and full width at half maximum(FWHM)of the PIT transparent window,can be adjusted by changing the length of the tooth-shape,the radius of the ring ring-shape resonator,or the interval distance.The proposed waveguide system has a slow light effect,the group delay time is up to 0.022ps,and the corresponding group index and group velocity are 8.72 and 0.115 c,respectively.These characteristics of this waveguide system indicate the potential applications in integrated optical circuits,such as slow-light devices,high-performance filters,and optical storage.(3)The plasmonic waveguide system consisting of a single tooth-shape and a single semicircle-shape directly coupled to a MIM straight waveguide is proposed and investigated by the FDTD method.Due to the interaction of the narrow discrete resonance and a broad spectrum caused by the tooth-shape and semicircle-shape,respectively,leads to the Fano resonance is obtained in the entire waveguide system.Simulation results show that the Fano resonance can be easily tuned by changing the parameters of the structure.These characteristics offer flexibility to design the devices.This nanosensor yields a sensitivity of 857nm/RIU and a figure of merit of 664.This section is significant for design and application of the sensitive nanoscale refractive index sensor.