# Graphene metamaterial absorber

Graphene, a single atomic sheet of carbon atoms arranged in a hexagonal lattice, has shown great promise for functional optical and optoelectronic devices. Compared to devices made of conventional materials, graphene-based devices have a unique tunability advantage since graphene’s conductivity can be drastically modulated by electrostatic gating.

Due to its atomic thickness, it is usually very difficult to model graphene in an FDTD simulation without using a large number of grid points. Fortunately, Tidy3D natively supports a surface conductivity model such that thin material layers can be accurately simulated even with grids much larger than the actual layer thickness. More specifically, you can model graphene directly using Tidy3D’s [Material Library](https://docs.flexcompute.com/projects/tidy3d/en/stable/material_library.html?highlight=material ibrary). The graphene’s conductivity is described by the well established Kubo formula, which includes the contributions from the intraband and interband electronic transitions. To define graphene, a few parameters, namely the scattering rate, chemical potential, and temperature, are required as user inputs.

This example demonstrates how to model a graphene fishnet metamaterial absorber in the THz frequency range. By forming a Fabry-Perot resonator between the graphene layer and a metal mirror, high absorption is achieved across a bandwidth of ~ 2 THz. The design is adapted from the seminal work Andrei Andryieuski and Andrei V. Lavrinenko, “Graphene metamaterials based tunable terahertz absorber: effective surface conductivity approach,” Opt. Express 21, 9144-9155 (2013) (opens new window).

To view the full example in Python, please click here (opens new window).