Graphene has excellent optical properties, with an absorption rate of about 2.3% over a wide wavelength range, making it almost transparent. Within the thickness range of several layers of graphene, with each increase in thickness, the absorption rate increases by 2.3%. Large area graphene films also have excellent optical properties, and their optical properties change with the thickness of graphene. This is an unusual low energy electronic structure possessed by single-layer graphene. At room temperature, a voltage is applied to a double-gate double-layer graphene field-effect transistor, and the bandgap of graphene can be adjusted between 0 and 0.25 eV. When a magnetic field is applied, the optical response of graphene nanoribbons can be tuned to the terahertz range.

When the intensity of the incident light exceeds a certain critical value, graphene's absorption reaches saturation. These characteristics allow graphene to be used as a passive mode-locked laser. This unique absorption may result in the input light intensity exceeding a threshold when saturated, which is called saturation effect. Graphene can easily saturate and strongly excite the near-infrared region due to global optical absorption and zero bandgap. Due to this special property, graphene has been widely used in ultrafast photonics. The optical response of the graphene/graphene oxide layer can be tuned electrically, and under more dense laser illumination, graphene may have a nonlinear phase shift optical nonlinear Kerr effect.

Mechanical properties

Graphene is one of the materials with the highest known strength, and it also has good toughness and can be bent. The theoretical Young's modulus of graphene is up to 1.0 TPa, and the inherent tensile strength is 130 GPa. The reduced graphene modified by hydrogen plasma also has very good strength, with an average modulus of up to 0.25 TPa. Graphene paper composed of graphene sheets has many pores, making it very brittle. However, After oxidation, functional fossil graphene can be obtained, and then graphene paper made from functional fossil graphene will be exceptionally strong and tough.