Coupling Manipulation And Functional Devices Of Graphene Plasmonic Metamaterials

To realize and control the light-matter interaction has always been an important subject in basic research.The surface plasmons is a surface wave formed by the collective oscillation of the free electrons on the metal-dielectric surface under the incident electromagnetic wave.It can localized the electromagnetic field in the subwavelength scale,resulting in a strong nearfield enhancement,thus greatly enhancing the light-matter interaction.Compared with conventional metallic surface plasmons,graphene surface plasmons has the characteristics of dynamic tunability,extremely strong energy localization and low loss,and are widely used in optical modulators,sensors,transformation optical devices,field effect transistors and other optoelectronic devices.Metamaterials,on the other hand,are composed of periodic or aperiodic subwavelength artificial units,which have a strong ability to manipulate electromagnetic waves.By combining graphene plasmons with metamaterials,the field localization,transmission and modulation of light can be realized through reasonable design.In addition,in these composite metamaterials,the plasmonic mode can be coupled with other optical resonance modes,which can dynamically realize the characteristics of spectral line modulation,energy transfer between modes,enhanced absorption,reduced bandwidth,localized optical field and so on.In this thesis,the coupling and manipulation of related modes in different graphene plasmonic metamaterials(including graphene plasmons,Tamm plasmon polaritons,magnetic polaritons,etc.)are studied theoretically and simulatively,and their applications in optoelectronic devices are also explored.The main research results of this thesis are as follows:(1)Three graphene-photonic crystal metamaterial devices are designed:(i)Combining dielectric grating,graphene monolayer and one-dimensional photonic crystal.Through proper design,the structure can realize the excitation of dual-band guided modes.By adjusting the chemical potential of graphene,the loss characteristics of graphene can be adjusted,and then the controllable absorption-induced switching effect can be realized.The absorption phenomenon can be explained by the classical coupled mode theory and impedance matching theory.(ii)Combining waveguide grating structure with classical Tamm plasmon structure,the interaction between graphene-based guided mode and Tamm plasmonic mode is studied.The results show that the designed structure can excite these two resonance modes and realize the perfect dual-band absorption in near-infrared band.When the incident angle is adjusted,the coupling between the two modes can be dynamically adjusted.The above two works have realized the perfect absorption of graphene in the near-infrared band and overcome the disadvantage of very low absorption of graphene in the near-infrared band.(iii)Combining graphene ribbon array with Tamm plasmonic structure,the interaction between localized graphene plasmons and Tamm plasmonic mode in infrared band is studied.The coupling effect of the two modes can be realized by adjusting the graphene chemical potential.Similarly,the interaction between nonlocalized graphene plasmons and Tamm plasmonic mode can be realized by replacing graphene ribbon array with a continuous graphene monolayer and introducing dielectric grating structure.These results are helpful to develop high-performance graphene optoelectronic devices,including sensors,modulators,detectors and so on.(2)Three graphene-based plasmonic metamaterial devices are designed:(i)Combining the composite metal grating structure and graphene monolayer.The simultaneous excitation of graphene plasmons and multiple magnetic polaritons can be realized by introducing slits with different depths.The simulation results and the coupled oscillator model reveal that multimode excitation can achieve multi frequency perfect absorption.In addition,the electromagnetic energy of different resonance modes can be selectively localized in different positions of nanostructures,which shows the unique characteristics of energy conversion.By adjusting the chemical potential of graphene,graphene plasmons can be strongly coupled with magnetic polaritons,resulting in significant mode splitting.(ii)Combining the metal grating with double-layer graphene.With the help of metal grating,the graphene placed on the upper and lower layers of metal grating and metal grating in the middle can excite two graphene plasmoic mode and magnetic resonance modes at the same time.In addition,different coupling phenomena can be realized by adjusting the chemical potential of upper and lower graphene at the same time or independently.(iii)Graphene localized plasmons can be excited by using a simple graphene periodic strip array.Combining with field programmable gate array,different electrical signals can be input to realize the multi-function of the device,including refractive index sensing,multi-channel absorption/reflection and harmonic generation.For the graphene plasmonic composite structures,the resonance of magnetic polaritons can be predicted by the classical capacitance-inductance model,the resonance of graphene plasmons can be predicted by the equivalent multilayer waveguide theory,and the multi-mode coupling process in nanostructures can be described by the classical coupling oscillator model.These results are helpful to the study of light matter interaction based on graphene,and to the development of related plasmon devices,including optical switches,thermal radiators,sensors and so on.(3)Three metamaterial devices based on other two-dimensional materials are designed:(i)Combining black phosphorus with two-dimensional photonic crystals.Through guided mode resonance,the anisotropic perfect absorption of black phosphorus is realized under the condition of critical coupling.According to the coupled mode theory,the composite system can show over coupling,critical coupling and under coupling for different electron doping of black phosphorus.Based on these different states,the composite structure can be used for different devices,such as phase modulation related devices(over coupling),perfect absorbers(critical coupling)and simple reflectors(under coupling).(ii)Combining black phosphorus with metallic grating.By designing appropriate structural parameters,the simultaneous excitation of black phosphorus surface plasmons and magnetic polaritons can be realized.By adjusting the electron doping of black phosphorus,the strong coupling between black phosphorus plasmons and magnetic polaritons can be realized.Considering the anisotropy of black phosphorus,the Armchair direction of black phosphorus is rotated 90 degrees to the Zigzag direction,and the strong coupling phenomenon disappears.In this work,the black phosphorus plasmons can be calculated by multilayer waveguide theory,and the magnetic polaritons can be calculated by capacitanceinductance model.The theoretical calculation is basically consistent with the simulation results.(iii)Combining tungsten disulfide with dielectric grating.Through reasonable design,the strong coupling between guided mode resonance mode and tungsten disulfide exciton mode can be realized.The coupling strength can be adjusted by adjusting the position of tungsten disulfide in the dielectric layer.In addition,the coupling process can be dynamically adjusted by adjusting the incident angle.These results provide a simple way to realize the optical two-dimensional material interaction,and help to develop compact,scalable and easy-to-fabricate optoelectronic devices.