CMOS-compatible long-range dielectric-loaded plasmonic waveguides

CMOS-compatible long-range dielectric-loaded plasmonic waveguides featuring long propagation lengths and strong mode confinements are designed and studied using the finite-element method. The waveguide composition includes a Si ₃N₄ ridge on the top of a thin metal stripe deposited on a silicon-on-insulator (SOI) wafer with a thin top SiO ₂ layer produced by thermal oxidation. All the materials chosen in the design are compatible with complementary metal-oxide-semiconductor technology and can be integrated with plasmonic, electronic and photonic components. Influence of various waveguide parameters on the waveguide characteristics is analyzed, including the thicknesses of the Si layer and the SiO ₂ layers, the dimension of the ridge, as well as the parameters of the metal stripe. It is found that, at the telecom wavelength of 1.55 μm, the propagation length of CMOS-plasmonic waveguides can reach 1.07 mm with a lateral mode confinement of ∼1.18 μm and 4.43 mm with a lateral mode width of ∼2.32 μm. The bending loss and coupling length are both calculated to evaluate the applicability of the proposed device for high density integration and a figure of merit is proposed to show the tradeoff between the propagation length and the lateral mode width in the application of plasmonic devices.