Analysis of mid-infrared graphene surface plasmons

The graphene plasmonic properties in the air–graphene–SiC (A–G–SiC) structure have been investigated in the mid-infrared region. The influences of the substrate on the dispersion properties and modal fields have been explored. The results show that in the low-wavelength region (<10.3 μm), due to the SiC substrate behaving like “dielectrics”, the plasmonic properties of the A–G–SiC structures are closely related to the graphene layer, supporting transverse magnetic (TM) modes with good confinement. But in the long-wavelength region, the SiC substrate manifests “metallic” property, and the plasmonic properties of the A–G–SiC structure mainly depend on the SiC substrate, leading to the effective index and loss decreasing drastically. For the transverse magnetic (transverse electric) modes, as the dielectric constant of the substrate increases, the loss increases (decreases), the modes decay much quickly (slowly) into the air. The results are very helpful to design novel graphene-based waveguides devices, such as modulators, detectors and filters.