Numerical Study On The Modal Characteristics Of Silicon-based Hybrid Plasmonic Waveguides

A silicon-based hybrid surface plasmon polaritons waveguide can not only overcome thediffraction limit to achieve subwavelength optical field constraints, but also reduce its loss so thatpropagation distance can reach to tens or even hundreds of magnitude wavelength. Therefore, thesurface plasmon polaritons waveguide provides effective learning for the future realization ofnano-scale photonic integration circuits or devices.A sub wavelength conductor-gap-silicon(CGS) hybrid surface plasmon polaritons waveguide istheoretically analyzed, which consists of a thin low-index layer sandwiched between a silver stripand a high index silicon structure. The guiding properties of surface plasmon polaritons waveguide,such as propagation length and mode field area, are investigated for different rib widths and silicagap layer thickness. As a result, an effective modal area of0.08μm2and the propagation length of430μm can be achieved simultaneously. Secondly, the silicon slab based CGS waveguide can beformed by increasing the width of silicon rib, and the guiding properties of the silicon slab basedCGS are investigated for different rib widths, silica gap layer thickness and Si rib heightness. Inaddition, more simple structure and CMOS compatible fabrication process make these conductorgap silicon plasmonic waveguide a promising candidate for realizing high integration densityplasmonic circuits. The numerical results showed thatthe structure can generate the larger effectiverefractive index value of2.8and the propagation length of1.74mm, moreover, it provides a morestrong confinement of the optical field at the5nm thickness SiO2gap. Thirdly, coupling length oftwo parallel CGS hybrid surface plasmon polaritons waveguides with the same parameters istheoretically analyzed, which is investigated for different rib widths, silica gap layer thickness andSi rib heightness. The numerical results showed that when rib width is100nm, silica gap layerthickness is5nm and Si rib heightness is0(i.e., silicon slab), the coupling length of the structurecan reach to105μm.