Investigation Of Terahertz Wave Propagation Properties Based On The Graphene-Metal Hybrid Microstructures

Terahertz?THz?waves lie between the microwave and infrared regions in the electromagnetic spectrum,showing great potential in wireless communication,object imaging and astronomical observation.However,there are few tunable functional devices that can effectively control terahertz wave.The narrow-band resonant curve with the high-quality factor is very important for the application of THz wave in the fields of biological sample detection,slow-light device design and photoelectric switch.Due to the interaction of light and dark modes in the asymmetric structure of metamaterials?MMs?,Fano resonance is excited,and has the advantages of lower radiation,Ohmic loss and the sharp spectral lines,which can well meet the application requirements of this aspect.Graphene not only has high electron mobility,but its conductivity can also be significantly changed in the THz band by altering the Fermi level,which is very suitable for making tunable devices.In order to obtain tunable terahertz waveguide functional devices with high performance,based on the hybrid structure of graphene-metal?or semiconductor?,we study the tunable properties of THz graphene modulator by using the finite integral method.The main results are given in the follows.?1?Based on the split-ring resonant ring MMs made of metal?or InSb semiconductor?,and with the whole graphene to be the active region,the tunable propagation properties of the hybrid microstructure has been investigated by controlling carrier concentration of graphene through bias voltage.The results show that when the Fermi level varies in the range of 0.01-0.30 eV,the amplitude and frequency modulation depth of the resonance in the InSb-graphene hybrid MMs structure are 26.0%and 43.4%.In addition,the highest quality factor?Q-factor?of resonance spectrum can reach more than 40.?2?By using the patterned-graphene microstructure as the active region,the tunable propagation properties of the periodic stripes microstructure are simulated in the terahertz region,including the effects of graphene Fermi levels,structural parameters,and operation frequencies.The results reveal that an obvious Fano resonance can be observed in the hybrid metal-graphene stripes MMs structure,the maximum transmission peak of Fano resonance can reach 0.97,and its Q-factor is more about 20.In addition,as for the graphene-graphene asymmetrical double-bars MMs structure,the frequency modulation depth of Fano resonance is more than 60%when the Fermi level of the graphene varies from 0.1 eV to 1.0 eV.?3?With the hybrid InSb-based stripes microstructure,a high Q-factor terahertz modulator is designed,and its resonance spectrum can be modulated efficiently by doping and changing the temperature of InSb.For the hybrid Cu-InSb MMs structure,the results show that the amplitude modulation depth of Fano peak can reach more than 80%when the carrier concentration of the doped InSb varies in the range of5×10¹⁶-5×10¹88 cm^-3.