Research On High Quality Factor Graphene Devices Of Terahertz Waves

Locating between microwave and far infrared spectral region,terahertz(1THz=10¹²Hz)waves show prospect applications in the fields of wireless communication,public security inspection,and space astronomy.Metamaterials（MMs）achieve artificial regulation of electromagnetic properties and provide a good platform for the development of terahertz devices.Based on the interaction of bright and dark modes of asymmetric structure,Fano resonance indicates a sharp spectral curves with a high Q-factor.Graphene has the advantages of high carrier mobility and good tunable property,which acts as a wonderful tunable medium.To obtain terahertz functional devices with high performances,based on the graphene supported asymmetric MMs structure,the tunable Q-factors THz devices have been investigated by using the finite integral method,including the effects of graphene Fermi levels,structural parameters and operation frequencies.The main results are given in the follows.Based on the graphene asymmetric double ellipse microstructure,an obvious Fano resonance can be observed by translating two ellipses along the polarization direction.If the asymmetry degree changes in the range of 6-18μm,the amplitude modulation depth of Fano peak reaches more than 75%,and the Q-factor is greater than 13.If the Fermi level changes in the range of 0.2-1.0 e V,the amplitude and frequency modulation depths（MD）are 5%and 46%,respectively.Additionally,a tunable THz absorber with two resonant peaks was demonstrated by utilizing the asymmetric graphene-graphene double strips microstructure.When the lengths of the two strips are 26μm and 16μm,two absorptions with values of84%and 90%are observed at 1.06 THz and 1.67 THz,respectively.By replacing the metal substrate with a uniform graphene layer,a bi-directional terahertz MMs absorber was also realized.If the terahertz wave is incident in the forward direction,the graphene double strips microstructure behaves a typical MMs absorbers,its absorption can reach 88%.if the terahertz wave is incident in the reverse direction,the graphene double strips microstructure behaves a Reflective modulator,and its amplitude and frequency MD will reach 81%and 49%.