Design of a long-range hybrid plasmonic waveguide with graphene-based electrical tuning of propagation length

Design of a long-range hybrid plasmonic waveguide with graphene-based electrical tuning of propagation length Long-range hybrid plasmonic waveguides (HPWs) have attracted significant research attention as they help to achieve ultra-low nanoscale mode confinement with low propagation losses. Here, we present numerical studies of long-range HPWs consisting of a combination of plasmonic metal thin films and nanoscale structures of a high refractive index material (such as silicon) with a low refractive index material (such as silica) surrounding the nanoscale structures and the plasmonic metal thin film. The HPWs show hybrid mode characteristics due to the interaction between dielectric modes and SPP modes. Moreover, electrical tuning of optical losses is formed by introducing partially overlapping graphene monolayers between silicon nanowires and plasmonic metal film. The tunability in the HPW is implemented by using graphene as an electro-absorption material. The effective refractive index and the corresponding propagation length obtained for these plasmonic waveguides using an Eigenmode solver demonstrate the viability of these hybrid plasmonic waveguides in applications that demand a long propagation range with reasonable field confinement. Moreover, we study the effect of the variation of different waveguide parameters on the propagation length and mode area. There is a significant electrical tuning of propagation length in graphene-based HPWs by applying an external voltage at the telecom wavelength of 1550 nm, owing to the strong field confinements between metal and silicon nanowires. The waveguides we proposed can be fabricated with relative ease using standard processes, and protocols for the fabrication of these hybrid plasmonic waveguides are provided in this paper. The proposed hybridization in nanoscale waveguides can be used in nanolasing, nanofocusing, sensing, switching, and subwavelength optical guiding applications in future nanoscale photonic/plasmonic integrated circuits.