Ultracompact Waveguide for an Optical Network-on-Chip with a Vacuum Gap Based on Surface Plasmon Polaritons

In an optical network-on-chip, optical waveguides play a crucial role in transmitting optical signals. Therefore, it is essential for optical waveguides to have a compact size and low insertion loss. This paper proposes a new type of optical waveguide with a vacuum gap based on surface plasmon polaritons. By utilizing surface plasmon polariton technology, the proposed waveguide reduces scattering attenuation caused by hybrid surface plasmon polaritons, saves space in the network-on-chip, and enables the integration of more devices on the chip while maintaining an ultracompact size requirement. Finite-Difference Time-Domain (FDTD) simulations and comparisons are performed between a conventional Si waveguide and two types of surface plasmon polariton waveguides. The results demonstrate that the designed waveguide exhibits excellent confinement capabilities even when the waveguide width is only 100 nm, with an insertion loss of 0.32 dB/μm. The relevant waveguide parameters are studied and optimized, providing a theoretical basis for the development of ultracompact gap surface plasmon polariton waveguides.