A Broadband Optical Modulator Based on a Graphene Hybrid Plasmonic Waveguide

In this paper, a graphene hybrid plasmonic waveguide (HPW) modulator, in which a single layer of graphene-hexagonal-boron-nitride-graphene (graphene-hBN-graphene) has been embedded to enhance the absorption of the graphene, is numerically investigated based on a three-dimensional (3D) finite-difference time domain. The influences of geometric parameters, chemical potential, and dispersion on the fundamental mode of this modulator were determined. The height and width of the low index material results in significant effects to the effective mode index, which can determine the performance of the optical modulator. Using appropriate geometric parameter settings, this modulator could simultaneously offer a large extinction rate (up to 39.75 dB), broadband modulation bandwidth (up to 190.5 GHz), low power consumption (as low as 7.68 fJ/bit), and also provide subwavelength field confinement and long propagation distances. Wide-range wavelength response studies show that this optical modulator has good wavelength tolerance from 1200 to 1800 nm, indicating that it may be employed as an optical device exhibiting the desired performance. Furthermore, this optical modulator is not only suitable for optical fiber communications but also for free-space optical communications Our simulation results may provide experimental guidelines for designing future high-performance graphene optical modulators.