Investigation On Graphene-based Plasmon-induced Transparency And Its Applications

With the rapid development of science and technology,the size of traditional electronic chips has basically reached the physical limit.Thus,the transmission speed,anti-interference ability,and capacity of carrying information of semiconductor products based on electronic chips have bottlenecks.Therefore,people are always looking for a new information carrier to replace electronics.Later,it was discovered that photons transmitting electromagnetic interactions have unique advantages in terms of transmission speed,anti-interference ability,and carrying information capacity.Especially the miniaturization of devices,which makes photon replacing electrons become a new trend.However,in actual applications,it is found that the size of the optical fiber is large and cannot be matched with a small photonic device at the interface.Therefore,the emerging discipline of surface plasmon optics is introduced,which can perfectly integrate the advantages of electronics and photonics in the nanometer size range,and provide a solution to the problem of size incompatibility.The core of surface plasmon optics is the material surface plasmons(SPs),which are a kind of oscillating wave generated by the resonance between the conduction electrons on the surface of insulators or metal materials and the photons in the light wave.Since SPs can break through the diffraction limit of light and localize the light in the nanometer range,it provides the possibility for implementing nanoscale electro-optical devices.In recent years,due to the dynamic tunability,wide frequency operating range,and strong locality of SPs,graphene-based miniature plasmonic electro-optical devices have been widely studied.In this paper,based on graphene SPs,the plasmon-induced transparent(PIT)phenomenon,which is the dominant optical abnormal transmission phenomenon,is used as a bridge.Using the Finite-difference time-domain(FDTD),coupled mode theory(CMT)and electromagnetic field theory,the optical properties and mechanisms of different patterned graphenes are detailed research,achieving micro-nano optoelectronic devices with different functions.The main research contents are as follows:Firstly,single plasmon-induced transparency(Single-PIT)based on single-layer patterned graphene metamaterial.1.The Single-PIT,which is destructive interference between the superradiation mode and the subradiation mode,is studied in a patterned graphene-based terahertz metasurface composed of graphene ribbons and graphene strips.Research shows the left(right)transmission dip is mainly tailored by the gate voltage applied to graphene ribbons(stripes),respectively,meaning a dual-mode on-to-off modulator is realized.Surprisingly,an absorbance of 50%and slow-light property of 0.7ps are also achieved,demonstrating the proposed PIT metasurface has important applications in absorption and slow-light.In addition,coupling effects between the graphene ribbons and the graphene strips in PIT metasurface with different structural parameters also are studied in detail.Thus,the result provides the possibility to realize a dual-mode photoelectric switch and multifunctional device.2.Single-PIT and single plasmon-induced reflection(Single-PIR)are realized in a patterned metamaterial consisting of four graphene blocks and a graphene strip.By controlling the Fermi level of graphene,Single-PIT and Single-PIR can be dynamically modulated.The excellent slow-light performance is interpreted by the group index of 630.Moreover,the reflectance of Single-PIR can reach 70%.Thus,this structure provides the possibility to achieve excellent slow-light equipment,reflectors and modulators.Secondly,dual plasmon-induced transparency(Dual-PIT)based on single-layer patterned graphene metamaterial.1.The patterned graphene composed of four graphene blocks and three graphene strips is placed in dielectric silicon to analyze and study the Dual-PIT and dual plasmon-induced absorption(Dual-PIA)characteristics of the graphene metamaterial.The Fermi level of graphene,carrier mobility,and surrounding medium environment are used to dynamically and statically control Dual-PIT and Dual-PIA.At the same time,the group index of 328 and the absorption rate of 93.5%are obtained,meaning the proposed metamaterial has excellent slow-light and absorption characteristics.2.An m-shaped graphene-based metamaterials is proposed,which can produce a dynamically tunable Dual-PIT by coupling among a dark mode and two bright modes.The result shows that when the Fermi level of graphene is low,the graphene exhibits lossy dielectric;conversely,it has metallic properties.Moreover,when the carrier mobility of graphene reaches 3m~2/Vs,the group delay of the proposed metamaterial can be as high as0.6ps,indicating that higher carrier mobility can realize the excellent multi-channel slow-light equipment.3.H-type-graphene-based slow-light metamaterials can realize an obvious Duak-PIT phenomenon,which can be dynamically modulated by Fermi level and carrier mobility of graphene.The simplicity of the structure and the continuity of graphene possess great advantages.In addition,the group index of 237 shows that it has certain application in the slow-light.Thirdly,Fano resonance based on double-layered patterned graphene metamaterial.A terahertz multifunction modulator composed of upper-layer double graphene ribbons and lower-layer a graphene strip,which can generate a Fano resonance produced by hybrid between a broad low quality factor mode and a narrow high quality factor mode,is designed.In comparison to other graphene-based terahertz modulators,the amplitude modulation depth can reach 99.57%,meaning an excellent electro-optic switch can be realized.Moreover,the extinction ratio of Fano resonance can reach 99.70%,demonstrating an unparalleled electro-optic filter is implemented.Finally,variations in the lateral and longitudinal lengths of the lower-layer a graphene strip enable excellent dual-band,triple-band filters.Thus,this research provides a new way to implement terahertz multi-function modulators.