Modeling a high-performance broadband mid-infrared modulator using graphene-based hybrid plasmonic waveguide

A graphene-based-hybrid plasmonic waveguide (GHPW) with a unique geometric structure is designed for surface plasmon polariton guidance and modulation at the frequency area of 10 to 30 THz. The GHPW consists of a graphene layer in the middle, a high-density polyethylene (HDPE) gating layer, two interior dielectric delimiter layers, and two exteriors semi-cylinder Germanium substrates symmetrically embedded on both edges of the graphene. Because of the matchless semi-cylinder structure design, the electromagnetic wave interaction with graphene ultimate subwavelength SPPs strong confinement with long propagation length. Small normalized mode area of ~10-4 and long propagation length of 10.67-28.92 μm at Fermi energy of 1.0 eV is attained for SPPs modes propagation of the GHPW in the frequency bound of 10-30 THz and semi-cylinder radius R > 450 nm, respectively. By controlling the graphene Fermi energy, it is found that the structure has a modulation depth higher than 20 % for the frequency band of 10-30 THz and arrives at the peak of approximately 100 % at a frequency greater than 28.75 THz. To benefit from the great broadband MIRpropagation and modulation efficiency, the GHPW may promise different MIR waveguides, modulators, photonic, and optoelectronic devices.