Optical Properties Of 1D Silver Nanograting Structure With Low Optical Loss

Various metallic nanostructures with smaller size and higher accuracy have been designed and fabricated out due to the increasing advances in nano-fabrication techniques. Surface plasmons supported by metallic nanostructures exhibits considerable novel physical effect of optics. The coupling between surface plasmon polarization and localized surface plasmon can further enhance the local electric field at metal and dielectric boundary, which holds great potential for applications in the research fields of surface enhanced Raman scattering (SERS), biosensors, and nonlinear optics.In this thesis, we will give detailed studies on the optical properties of one dimensional silver nanograting structure with low optical loss and its application on SERS. The thesis is mainly composed of two sections that are arranged as following:1. The methods for the preparation of low loss one-dimensional silver nanograting structure and its structural characterization are introduced. We first use focused ion beam (FIB) technology to fabricate one-dimensional dielectric nanograting structure on a silicon wafer. Than using magnetron sputtering method, silver film on the surface is deposited. Finally, copper plating on the silver film and peeled the metal film together, the one-dimensional silver nanograting structure with smooth surface is achieved. We also use FIB technology to prepare the corresponding one-dimensional silver nanograting structure with rough surface directly on silver films deposited on a silicon wafer by magnetron sputtering method. Both the two nanostructures are characterized by scanning electron microscope (SEM) and atomic force microscopy (AFM).2. We investigate the optical properties of one dimensional silver nanograting structure with low optical loss and its application on SERS. We use FDTD method to optimize structural parameters of the one-dimensional silver nanograting for achieving strong enhanced local electric field. The dispersion relation and surface plasmon propagation length of the above two one-dimensional silver nanogratings are investigated both experimentally and theoretically. The one-dimensional silver nanograting with smooth surface has a longer propagation length, which exhibits less optical loss. Further through SERS experiment, the enhancement factor of the one-dimensional silver nanograting with smooth surface is increased by about 50 times compared to the one-dimensional silver nanograting with rough surface. Our low loss one-dimensional silver nanograting structure with smooth surface can serve as an effective SERS substrate.