Optical Tunable Filters And A Wavelength Demultiplexing System Based On Surface Plasmon Polaritons

Surface plasmon polaritons (SPPs) is considered as a potential carrier of energy and information by many scientists. They believe it will be widely used in future optical communication field.It can break the diffraction limit which exists in the field of traditional optics and guide the light at sub-wavelength range, and make the light propagate farther in an effective length. Optic devices based on surface plasmon not only have the advantage of a high-speed response which is owned by photonic devices, but also have the advantage of a small-scale which is owned by electronic devices. It make the realization of high-speed all-optical devices in sub-wavelength scales be possible. For optical communications, the wavelength selection is a critical technology. It is very useful and helpful for the high integration of the future optical communication to make optical tunable filters and wavelength demultiplexing structures using the properties of surface Plasmon within the scope of sub-wavelength.The main contents of this paper:In chapter1and chapter2, we have discussed the development process,the research methods and basic principles of surface plasmon polaritons, elaborated the excellent characteristic of MIM waveguides, described an important role of resonance cavities in surface plasmon filters and given some example of the relevant resonators structure has been proposed by researchers at present, and had anoutlook of the application prospect of filtersand the wavelength demultiplexing systems in the future optical communication.In chapter3,the enhanced transmission of a metallic photonic crystal slab filled with different linear media in the hole-structure is investigatedtheoretically.The results show that the enhanced transmission peaks exhibit a red shift when the relative dielectric constant of is increased. By varying the thickness of the linear media filled in the hole-structure, the enhanced transmission peak generated by the hole-structure has a great shift and the one generated by the surface plasmon moves slightly. By changing the position of the linear medium,these two enhanced transmission peaks have no significant shift. Thus, we can achieve wavelength selection by changing the parameters of the structure tocontrol the position of the enhanced transmission peaks. This is very useful for the production of surface plasmon filters.In chapter4, we proposed a band-stop filter based on side coupled equilateral triangle resonatorand the metal-dielectric-metal surface plasmon waveguide at first, which is a very novel and simple structure. It is easy for modern technology to fabricate such kind of structure.By theoretical analysis of the nanometer scale equilateral triangle resonant cavity, we can find that it is easy totunable the center wavelength of the band-stop filter by changing the side of the equilateral triangle resonant cavity or varying the media filled in the resonant cavity. It is consistent with the simulation result we obtainedby applying the finite element method (COMSOL) using perfectly matched layer as a boundary condition. Further, the transmission spectrum bandwidth can be adjusted by changing the coupling distancebetween the equilateral triangle resonator cavity and the MIM waveguides. The results obtained by COMSOL simulation can be explained very wellby temporal coupled mode theory.This proposed band-stop filter can be used in the sub-wavelength range and have a very large potential application value in the highly integrated circuit based onthe surface plasmon.Then, we make simple changes of the band-stop filter mentioned above by verifying the equilateral triangle resonator from side coupling to direct coupling, resulting in a narrow band of an band-pass filter. By using the finite element method, we make a detail simulation analysis of the relationship between characteristics of the transmission spectrum of the band-pass filter and its structural parameters. Conclusions show that the central wavelength of the band-pass filter andthe side length of the equilateral triangle cavity have a linear relationship.As the side length of the equilateral triangle cavity is increased, the center wavelength of the band-pass filter has a red shift. It also leads to a lower transmittance for the loss is increased. Further, the coupling distance between the equilateral triangle resonator and the MIM waveguide isa critical factor to adjustthe band-pass filter.As increasing the coupling distance, the center wavelength of the band-pass filter has a little blue shift, but the transmission rate has a significant reduction.However, the full width half maximum is reduced too. Therefore, we can adjust the bandwidth of the band-pass filter by changing the coupling distance between the equilateral triangle resonator and the MIM waveguide.Finally, we have proposed a novel wavelength demultiplexing structure based on asurface plasmon equilateral triangle resonator. By applyingthe COMSOL simulation method, we verified that the surface plasmon wavelength demultiplexing structure with three channels can successfully select three different brands.In conclusion,on one hand,we analyzethe enhanced transmission of the metallic photonic crystal slab filled with linear media in the hole-structure.The results show that we can adjust the position of the enhanced transmission by varying the relevant parameters of the structure. It provides some references to produce an optical filter. On the other hand, we propose a band-stop filter, a band-pass filter and a wavelength demultiplexing structure based on an equilateral triangle resonant cavity. respectively. Then, we analyze these structures theoretically. Meanwhile, the results of simulation achieve a high agreement with the theoretical analysis. All structures proposed in this paper can be achieved within the sub-wavelength range which meets the development requirements of the future highly integrated optical communication.