Design,fabrication And Propagation Properties Of Novel Plasmonic Waveguides

Surface plasmons are essentially electromagnetic waves trapped at metal-dielectric interface because of their interaction with the free electrons of the metal,which are very sensitive to the nanostructures on the metallic surface.It is shown that surface plasmons can achieve extremely small mode wavelengths and high localized electromagnetic fields.Hence,plasmonics with deep subwavelength characteristics may break the diffraction limit of light,which are promising for modulating photons on nanoscales,and thus has attracted great interest for decades.So far,The SP-inspired research,on the application side,includes extraordinary optical transmission,surface enhanced Raman spectroscopy,sub-wavelength imaging,electromagnetic induced transparency,perfect absorbers,polarization switches,plasmonic nano antenna,etc.;and on the fundamental side,includes plasmon mediated light-matter interaction,such as plasmonic lasing,plasmon-exciton strong coupling,etc.Surface plasmon is promising information carrier in the next generation for its unique properties such as the strongly electromagnetic field localization(on nano scale),light transmission speed,and local field enhancement.As a fundamental device in the integrated plasmonic circuits,plasmonic waveguides have attracted much attention and been widely studied.In this thesis,we have systematically studied the design,fabrication and propagation properties of novel plasmonic waveguide in both experimental and theoretical aspects.The Specific contents are as follows:First,we have experimentally and theoretically studied the coupling rules between light and surface plasmons in the plasmonic waveguide base on metallic nanowires,and surface plasmons propagating properties along the metallic nanowires.On one hand,we have designed several kinds of coupling nanostructures on the metallic nanowires,calculated the coupling efficiency between the light and surface plasmons in these nanostructures,and revealed the influence rules between the coupling efficiency and geometry parameter in nanostructures and the substrate.By optimizing the coupling nanostructures,surface plasmons propagating in unidirectional way along the nanowires are achieved.On the other hand,based on Maxwell equations,we firstly achieve the dispersion relation in the metallic nanowire systems with rigorous coupled wave analysis(RCWA)method and finite-element method(FEM)method,and then inquire to the surface plasmon mode properties such as mode propagation length and mode area,and lastly we theoretically and experimentally show that the suface plasmon propagate in a wide feruency range in the metallic nanowires system.Second,we demonstrate that by cascading nano-corrugation gratings with different periodicities on silver nanowires atop silicon,different colors can be spatially separated and chronologically released at different grating junctions.The released light frequency depends on the grating arrangement and corrugation periodicities.Hence the nanowire acts as a spectral splitter for sorting/demultiplexing photons at different nano-scale positions with a ten-femtosecond-level interval.Such nanowires can be constructed further into compact 2D networks or circuits,and provide a unique approach for integrating nanophotonics with microelectronics.Third,we have experimentally and theoretically studied band modulation and in-plane propagation of surface plasmons in composite nanostructures with aperture arrays and metallic gratings.It is shown that the plasmonic band structure of the composite system can be significantly modulated because of coupling between the aperture and grating.By changing the relative positions between these optical components,the resonant modes would shift or split.And the resonant SP modes launched on the structure surface can be effectively modified by the geometric parameters.Further,we provide an experimental observation to directly show the SP in-plane propagation by using far-field measurements,which agree with the simulated results.Our study offers a convenient way for observing the SP propagation in far field,and provides unique composite nanostructures for possible applications in subwavelength optodevices,such as optical sensors and detectors.In summary,in this thesis we have experimentally and theoretically studied the design,fabrication and propagation properties of one-dimensional and two-dimensional plasmonic waveguides.On the one hand,it reveals the coupling rules between light and suface plasmons in plasmonic waveguide based on nanostructured metallic nanowires,founds the novel characteristics of spectral spatial splitting and temporal delay,and structures the prototype device of spectral splitting with nano-scale spatially separated and femtosecond-level interval on chip.On the other hand,it reveals the band modulation and in-plane propagation in two-dimensional hybrid plasmonic waveguide system composed of aperture arrays and metalic grating structures,and develops an experimental method to observe the in-plane propagation properties in far field,which gives the propagation characteristics of the two-dimentional hybrid plasmonic waveguide system.Research results can be applied to the develop subwavelength photonic materials and devices,used in multi-functional integrated photonic chip,spectrometer on chip,surface plasmons multiplexers and subwavelength optical information parallel processors.