Control And Propagation Of Electromagnetic Wave In MIM Subwavelength Plasmonic Waveguide

Surface plasmon polariton is a kind of electron densitywave whichpropagate along the interface between the metal and the medium, generated by theinteraction of free electrons and electromagnetic fields. It has a range of uniqueoptical properties, such as the local electric field enhancement, the sub-wavelengthelectromagnetic wave localization, nonlinear enhancement and so on. The SPPspropagate along the interface between the metal and dielectric with decayingexponentially in the vertical directions, and we can control and modulate the SPPs bymodifying the morphology of the interface and environments near the interface. Withextensive research in recent years, the SPPs are widely used in transmissionenhancement, negative refractive index materials, super-resolution imaging,biosensors, etc. With the development of processing and preparation ofmetamaterials and the theoretical analysis and numerical simulation tools, more andmore subwavelength SPPs devices are theoretically analyzed and experimentallydemonstrated. Comparing with traditional optical devices which are restricted by thediffraction limit, SPPs devices can be achieved on the size of the micro-nanosubwavelength scale. In these devices, it is various types of waveguide that boundand guide SPPs, such as metal nano-array structures, rectangular slot waveguideheterostructure waveguide, V-groove waveguide, and MIM waveguides. Accordingthe properties of bounding and guiding SPPs, MIM waveguide get widely studiedbecause of the better bounding effect of SPPs，smaller size and easy processing. Ithas a vital importance to study theoretically the properties of MIM waveguides andmodulate the propagation of SPPs. Based on the above, we design micro-nano opticdevices based on MIM waveguide, and discuss the electromagnetic wavepropagation characteristics of these structures by numerical analysis method.The main work and results of this study can be simply summarized as follows:1、A single U-shaped resonant ring was added into MIM waveguide and weexplore the influence of different parameters of the waveguide and splitting ringresonators (SRRs) on progagating properties of MIM waveguides. We found thatwith the arm length of SRRs increases, resonant wavelengths of the waveguide redshift. If MIM waveguide is widened, the waveguide resonances approach toconstant resonances.2、Another resonant ring was added in the waveguide, then it became doublering resonator structure. Through numerical analysis, we found that the twotransmission resonant dips are symmetric and antisymmetric modes. With thedistance between two resonant rings being gradually enlarged, two transmission dipsgradually overlap each other, until they merge into one transmission dips.3、U-shaped metal resonant rings were periodically arranged in the MIMwaveguide. Periodic MIM waveguide transmission spectra exhibit two bandgaps, andthen we explored the influence of various parameters on the waveguide bandgaps:Bragg bandgap blueshifts with the period decrease. If arm length of the resonant ringincreases, both bandgaps will move to the long wavelength side. The width of twobandgaps increases with the width of MIM waveguide decrease.4、The structure of periodic MIM waveguide was changed. Through thetransmission spectra, we found that double bandgaps also appeared in the structure;locally resonant bandgap will move to the long wavelength side as the arms of thelong U-shaped ring resonator increases. Increasing the width of short U-shaped ringresonator can widen the Bragg bandgap width and make both bandgaps blueshift.Increasing the width of air will make two bandgaps move to the short wavelengthside and the width of two bandgaps decreases at the same time.5、A kind of filter was designed, the transmission property of1400nm can beadjusted by change position of the vertical air waveguide, and we can also move thebandgap by change length of the air waveguide.Through analysis of the structures above, we hope it can provide a reference fordesign of two dimensional subwavelength metal micro-nano optical devices in thefuture.