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Several Nanophotonics Devices Based on Surface Plasmon Polaritons

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Tutor: SunZuo
School: Nankai University
Course: Optics
Keywords: nanophotonics devices,MIM structure,multi-functional all-opticallogic gates,Fano
CLC: TP212
Type: PhD thesis
Year:  2013
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Nanophotonics is a newly developing and exciting field. By nanophotonics one usually refers to the science and devices involving structures with sub-micron dimensions (specifically less than100nm) and which are interacting with photons. Surface plasmon polaritons (SPPs) are electromagnetic excitations propagating at the interface between a dielectric and a conductor, evanescently confined in the perpendicular direction. Currently, in the proper consisting of metal and dielectric waveguide structure, electromagnetic fields is confined over dimensions on subwavelength can be used to produce highly integrated nanodevices. SPPs is now known as Plasmonics which is a major part of the fascinating field of nanophotonics. Metal-insulator-metal (MIM) waveguide is a typical SPPs waveguide. By using characteristics of MIM waveguide, numerous plasmonics device have been numerically and/or experimentally demonstrated, such as splitters, wavelength demultiplexer, Mach-Zennder interferometers, all-optical switches, nanofocusing, networks, and so on. This thesis focuses on nanophotonics devices of multifunctional all-optical logic gates, sensor, and filter in MIM structure.The first chapter introduces the characteristics of the multilayer film structure surface plasmon polaritons, and then describes the application of nanophotonics based on SPPs, especially a variety of nanophotonics devices with the MIM structure, and finally introduced numerical methods in the design of nanophotonics devices and the model of dispersive media in the numerical calculation.In the second chapter, we use the FDTD method to study multifunctional all-optical logic gates in the multilayer film structure. Theory and numerical calculations show that by tuning the coupling distance of metal gap waveguides, one can integrated AND, OR, NOT, and XOR logic gates in a multi-layer film structure. The coupled equations and the corresponding eigenmode was given, and so as the light intensity of each of the different output ports. In this work, the light intensity of each of the different output ports is strongly dependent on the thickness of the metal in the metal nano-gap waveguide arrays, which is due to the thickness of the metal film has a tremendous impact on the coupling coefficient. The extinction ratios of AND, OR, XOR, and NOT operation in multifunctional all-optical logic gates are4.1dB,11.1dB,18.0dB, and18.7dB, respectively.In the third chapter, a novel symmetric plasmonic structure which consists of an MIM waveguide and a rectangular cavity is proposed to investigate the Fano resonance performance by adjusting the size of the structure. The Fano resonance originates from the interference between a local quadrupolar and a broad spectral line in the rectangular cavity. It is realized that tuning the Fano profile by changing the size of the rectangular cavity. The nanostructure is expected to work as an excellent plasmonic sensor with a high sensitivity of about530nm/RIU and a figure of merit (FOM) of about650.In the fourth chapter, a plasmonic waveguide filter based on three cascaded nanodisks is proposed. By tuning the radius of cascaded nanodisks at telecommunication wavelength1550nm, the filter has a high transmittance (approximately90%) and a high Q factor (approximately60). The cascaded nanodisks support a united resonant (UR) mode. Light is trapped in the middle nanodisk when the UR mode exists. This phenomenon leads to the efficient transmittance and high Q factor of the plasmonic filter. The resonant wavelength and Q factor can be easily modulated by the radii of the nanodisks and the width of the waveguide.In the fifth chapter, the thesis is summarized and outlook of the further studies on nanophotonics devices are discussed.
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