Exciting plasmonic modes of metallic nanostructures loaded on silicon waveguides surface

Metallic nanoparticles shows interesting optical response because of the phenomena of localized surface plasmon resonance (LSPR) in it. These LSPR modes of metallic nanoparticles always have sub-wavelength features which are considered to be useful in the design of highly compact optical devices. But in many previous works, the optical response of these nanoparticles (single or mass) are collected through free space coupling into spectrometers or other instruments, which is still in a macro style. Recently, some researchers studied the optical properties of silicon waveguides with metallic nanoparticles embedded in it, in order to construct high performance optical components with a highly compact volume. The nanoparticles are always embedded inside the waveguide or located in a gap cut cross the waveguide to enhance the light-nanoparticle interaction as optical energy is mainly concentrate inside the silicon core. However, this will make the fabrication process more complex and rise up the fabrication cost, besides, the cut of the waveguide will cause extra energy loss unavoidably. In this paper, we numerically study the excitation of LSPR mode of metallic nanoparticles loaded on the waveguide surface, which is much easier for fabrications compare with those works where nanoparticles are embedded inside or located in a gap cut cross the waveguide. By examine the interaction of nanoparticles (nano split-rings, nano-strips) with different waveguide modes, we show how to efficiently excite the LSPR mode about a metallic nanoparticle which located on the surface of a silicon waveguide. Besides, through further analysis, we found that metallic nanoring loaded on silicon waveguide exhibits richer optical response, by carefully choosing the geometry parameters of both the ring and the waveguide. These findings may provide new ideas in designing of hybrid nanoparticle-waveguide system to construct highly compact devices for optical communications, optical sensing, and other areas.