Plasmonic-based SOI waveguides with non-rectangular silicon cores for enhanced optical performance

Abstract Optimizing optical waveguides for compact photonic integrated circuits requires the development of modified technologies capable of supporting signal routing in dense optical components. Implementing more integration density while ensuring signal integrity requires designing and implementation of compact optical waveguides with improved light confinement within subwavelength waveguide structures. The continued miniaturization of optical waveguides demands exploring advanced technologies to enhance the characteristics of the conventional silicon-on-insulator (SOI) waveguides. Exploiting the plasmonic effect to enhance the light confinement in small-size waveguides represents a particularly promising approach. In this work, three core geometries – rectangular, trapezoidal, and triangular – are designed and analyzed using a full-wave finite-integration time-domain (FITD) solver. The analysis extends to evaluate field distribution, propagation characteristics, and S-parameters across the 1.4–1.6 µm wavelength range. Findings show that non-rectangular geometries can reduce modal attenuation and modify effective mode profiles, with triangular cores exhibiting improved confinement and reduced metal-induced loss. The results reveal an improved performance with the triangle-shaped core cross-section waveguide where the loss is reduced to less than −2 dB compared to the rectangular waveguide.