▎ 摘　　要

Terahertz electromagnetic spectrum has long been recognized as an important region for scientific research. A new efficient broadband modulator for terahertz waves at room temperature can be realized using double layer graphene. The modulator is mainly composed by graphene-Al2O3-graphene three layers structure, with the carrier density of graphene modified by bias voltage, the absorption can be modulated quickly. The plane wave scattering and absorption by electric biased graphene are studied by the equivalent circuit method. This simplified equivalent circuit has good transportability, which is easy to calculate. The graphene based THz modulator has advantages like low cost, excellent tunability and easy to control, thus promising for THz system applications.