Frequency Shift in Tunable Electromagnetically Induced Transparency-like Metamaterials

Tunable electromagnetically induced transparency-like (EIT-like) metamaterials exhibit extremely high modulation depth and sensitivity, and are widely applied in sensors, modulators and filters. However, frequency shift may occur in the process of regulation, and this law has not been discovered yet. In this work, we reveal the law of frequency shift in tunable EIT-like metamaterials. Based on bright-dark coupling mode and bright-bright coupling mode, two EIT-like metamaterials with simple structures are proposed. The transmission amplitude and frequency of EIT-like effect can be dynamically controlled by tuning the Fermi level of graphene. The law reveals that the frequency of EIT-like effect shifts only when the damping rates of both coupling modes change and the change of one damping rate cannot shift the EIT-like effect. The conclusion can be verified by two-particle model. Due to the universality in tunable EIT-like metamaterials, the law can reduce the blindness of building models in metamaterials and improve the efficiency of structural design. Our work shows great practical prospect in terahertz modulators, optical switches and buffers.