Tunable Optical Properties Of Multilayers Containing Graphene

Up to now,the research on photonic crystal has exceeded 30 years.In recent years,dispersive photonic crystals have attracted much attention.The photonic crystals have many excellent characteristics including photonic forbidden gap and photonic localization.They can be used to produce new photoelectric devices,such as color displays,sensors,lasers,high efficiency light emitting diodes,data memories,photonic crystal antenna and so on.Due to the existence of photonic band gaps,which have many important applications in the fabrication of high performance devices,such as lossless reflectors,photonic crystal fibers,high quality optical microcavity.Graphene is a semi-metallic material consisting of a layer of carbon atoms with a two-dimensional honeycomb crystal structure.It has attracted much attention because of its remarkable electronic,mechanical and optical properties.Because of its unique electrical conductivity and low resistivity,graphene can be used in LED lamp,high-performance transistor,absorbing coating,solar cell,sensor,transparent electrode,transparent display and photodetector.However,because the devices such as photodetectors require strong interaction between materials and light,the weak interaction between graphene and light will limit its application.Therefore,how to improve the strong interaction of graphene with light has become a hot topic in recent years.Electromagnetic surface state can change the distribution of the electromagnetic field in the space,change the intensity of the magnetic field,so that the magnetic field is localized and the intensity of the magnetic field increases,and the intensity of this enhanced magnetic field can be used to design the absorption of the enhanced light.At present,the main physical mechanisms to enhance absorption include surface plasmon resonances,optical Tamm states and F-P cavity resonance.Due to the high localization of electromagnetic field based on surface states,we can to enhance the optical absorption for the graphene.Moreover,we can fabricate optical sensors,polarization lasers,optical switches,photodetectors,optical sensors,and etc.Here we place graphene on the surface of the multilayers to achieve enhanced optical absorption.Some studies have been carried out.In the second part of the thesis,we mainly studied the optical properties of one-dimensional photonic crystals with graphene on the surface enhanced optical absorption in the infrared range.In this section,the structure is designed to cover graphene on the surface of one-dimensional photonic crystal heterostructure.Because the conductivity of graphene is related to the Fermi level in the infrared range,the refractive index of graphene can be changed by altering the Fermi level of graphene.It is found that the absorption can be enhanced by changing the period number of the photonic crystal,the thickness of the each layer and the order of the dielectric layer,the layer number of graphene and the Fermi level of graphene.Compared with the structure only containing graphene,the absorption can be increased to exceed 4 times.In the third part of the thesis,the absorption properties of graphene based multilayers are studied.Based on Bloch surface states,perfect optical absorption is realized in structures containing the graphene,multilayer and the semicircle prism.Such results are important for futural experimental research and design new optical sensors which are sensitive to both angle and wavelength.