▎ 摘　　要

We theoretically investigated a graphene-based silicon electro-absorption modulator in both isotropic and anisotropic graphene models. Regardless of the graphene model, the optical transmission increases with the chemical potential of graphene because of the Pauli blocking principle. However, we found that the modulator based on the isotropic graphene exhibits an abrupt decrease in transmission for the transverse-magnetic (TM) polarization mode due to the epsilon-near-zero effect in the isotropic graphene at a certain chemical potential. Conversely, the anisotropic graphenebased modulator exhibits no such transmission dip. These particular behaviors provide us with a simple and easy experimental way to confirm whether graphene is an isotropic or anisotropic material. To further enhance the transmission dip in the isotropic graphene model, we suggest a simply modified modulator structure that increases the transmission depth by similar to 0.5 dB/mu m for the TM polarization mode.