Study Of Graphene And Metamaterial-based Nanophotonic Structures For Absorption

Though property of the metamaterial-based perfect optical absorption has been widely studied in THz,infrared and visible regime,but less attention has been paid to the working waveband of ultraviolent.However,few reports were found in the literature regarding the absorber in violet region.The absorber in ultraviolet region plays an important role in many applications such as nano-photolithography,nano-imprinting,biosensing,and photovoltaic,whereas,it is a crucial component in the systems for the applications.Considering this,we put forth the study of the perfect absorber working in ultraviolet region.In this thesis,we presented numerical designs and computational simulation of perfect optical absorption working in entire ultraviolet band using a simple Si substrate-based metamaterial structure.Our calculation results demonstrate that it can even reach to the level of as high as 99% in a certain local near waveband.Graphene,a two-dimensional form of carbon with its atoms arranged in a honeycomb lattice,has attracted more and more attention in recent years because graphene has been proved to possess unique mechanical,electric,magnetic and thermal properties.Therefore,graphene has a wide range of application in opto-electronic devices such as ultra-fast lasers,optical modulators,graphene-integrated photodetectors,and optical absorbers.Metamaterials(MTMs),with sub-wavelength size and metal-dielectric structures,show unique electro-magnetic property attributing to resonance excited by the incident radiation.The MTMs have highly dispersive material parameters and perfect impedance,and can produce unusual optical phenomena which are not found in natural material,as well as perfect optical absorption and negative refractive index.Many applications of metamaterial-based perfect optical absorbers with broad-or narrow-band of electromagnetic spectrum have been reported before.Here we use MTMs as a substrate of the absorber for the purpose of realizing near perfect absorption over a broadband spectrum.In this thesis,we pay more attention to its characteristic of high transmittance in optical regime.And the enhanced interactions-induced geometric resonance between graphene layer and cylinder particles layer is highlighted.The resonance can be well explained by means of the equivalent T circuit model.Our calculated results demonstrate that the simulation results are in good agreement to that of the theoretical model.