Study Of Active Long-Range Surface Plasmon Polariton Waveguide Devices

Surface plasmon polaritons (SPPs) is a wave of longitudinal charge oscillationsof the conduction electrons at the metal surface. A transverse magnetic (TM)polarized optical surface waves can propagate along the interface between a metal anda dielectric, it decays exponentially into both medias with a small penetration depthdue to the internal damping in metal, which limits the propagation distance. TheSurface plasmon polariton wave could break through the limitation of traditionaldiffraction and bring light to sub-wavelength scale photonic circuit, it has a broadapplication prospect of implementation the miniaturization and integration oftraditional devices and plays an important role in such as biological sensors,nanometer etching, storage of subwavelength optical data. Metal absorption can notignored due to the strong bound of SPP, to some extent, limits its application. Toreduce the propagation loss of waveguide, we use P(MMA-GMA) as the claddingmaterial in this paper. Using lithography and KI wet etching process to launch theresearch from the following several aspects:(1) The basic theory of SPPs. Deduce SPPs and its dispersion relation, adopt two-dimensional model of surface plasma wave shown the related theory. In view ofadvantage and disadvantage of the existing three methods and adopt thewaveguide exciting method to excite SPPs.(2) The fabrication of Long-range surface plasmon polariton waveguide. Fabricatemetal stripes on polymer cladding by conventional single-step liftoff methodswill lead to the formation of sharp pin-like and shark-fin-like structures on theedges of the metal stripe, which is unfavorable to mode control and increasesoptical loss. We creatively using photoresist as mask of waveguide, and prepareLRSPP waveguide by KI wet etching. During these processes, SEM and AFMare used to characterize the morphology of devices. The results shown, thewaveguide is well enough to meet the requirement of transmitting SPPs. Werealized the coupling of SPP and near-infrared light, and obtained the output, propagation loss and response time of the device. Experimental results shownthat the LRSPP waveguide fabricated by KI wet chemical etching method couldrealize low loss optical transmission in near infrared wavelengths. It has a goodapplication especially in optical-electronic devices.(3) Fabrication and performance test of LRSPP waveguide with M-Z structure. Giveout the structure and fabrication processes of device, and adopt ICP method toetch electrode structure, we find that the device has a better limitation of light, italso can realize switching characteristic, the rise time and fall time are150μsand268μs separately.(4) Fabrication and performance test of LRSPP-SU-8vertical coupling device. Takeadvantage of vertical coupling structure to realize light transmission between twowaveguides. Comsol is used to simulate and optimize the design of SPPwaveguide, the characterization results shown the effectiveness of experimentalprocess. When the width of Au waveguide and SU-8waveguide are6μm and5μm, respectively，and the coupling length is2500μm， we can obtain theoutput of device.