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 ۱۰ to ۳۰ 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 ~۱۰-۴ and long propagation length of ۱۰.۶۷-۲۸.۹۲ μm at Fermi energy of ۱.۰ eV is attained for SPPs modes propagation of the GHPW in the frequency bound of ۱۰-۳۰ THz and semi-cylinder radius R > ۴۵۰ nm, respectively. By controlling the graphene Fermi energy, it is found that the structure has a modulation depth higher than ۲۰ % for the frequency band of ۱۰-۳۰ THz and arrives at the peak of approximately ۱۰۰ % at a frequency greater than ۲۸.۷۵ THz. To benefit from the great broadband MIRpropagation and modulation efficiency, the GHPW may promise different MIR waveguides, modulators, photonic, and optoelectronic devices.

Keywords:

Graphene , Plasmonic , Waveguide , Modulator , mid-infrared , Finite element method