Polarization Properties Of Graphene And Its Optical Applications

Graphene,a two-dimensional carbon isomer with zero band gap and atoms arranged in regular hexagonal densities,exhibits unique mechanical,thermal,electrical,magnetic and optical properties and is used in a wide range of applications including electronic components,optoelectronics,solar cells,energy storage devices,displays,touch screens and sensing.The thesis begins with a brief overview of graphene optoelectronic properties and the research progress in applying them to biosensing,which is the background and significance of this thesis.In response,the research work is presented in three separate areas:Firstly,the common preparation methods of graphene and its characterization are described,and we have prepared graphene by an improved low-pressure chemical vapor deposition method.Here,we have used extremely volatile oxygen-rich alcohols（ethanol,isopropanol,etc.）as carbon source precursors,which were directly cleaved at high temperatures to produce carbon atoms and deposited onto the surface of a quartz glass substrate,and characterized the morphological structure and other features of the graphene glass.Secondly,the graphene sandwich coupling structure used in this study is proposed by comparing the polarization characteristics of graphene and Au films.This research has presented the enhanced interaction of light with graphene in this structure,as well as the polarization-sensitive absorption and broadband absorption properties.In our experiments,the surface plasmon resonance phenomenon of Au nanofilms was verified.We have also compared the respective polarization absorption effects of graphene and Au films under total internal reflection conditions by simulating the matrix transfer of multilayer dielectric films,highlighting the saturation absorption properties,broadband absorption properties,refractive index change sensitive properties and ease of tuning of graphene.Moreover,these polarization optical properties of graphene are relatively stable.Thirdly,a broadband and ultra-sensitive detector with nanosecond response has been developed for mechanical wave detection by using the polarization absorption effect of graphene,low refractive index dielectric sensing sensitivity and ultra-fast optoelectronic response.Mechanical waves can lead to rapid refractive index changes of the liquid near the graphene layer and the absorption difference between transverse electric wave and transverse magnetic wave by the graphene-based sandwiched structures is very sensitive to small refractive index variations(1.7×10^-8RIU).Hence,graphene-based ultra-sensitive detector has achieved high mechanical wave detection sensitivity of about 0.18 k Pa by differential detecting of the reflected transverse electric waves and transverse magnetic waves.Compared to other detector devices,this device displays remarkable features,i.e.the graphene-based ultra-sensitive detector exhibits a wide bandwidth（0-105 MHz）and an ultra-fast response time（～8 ns）.Moreover,broadband and ultra-sensitive graphene-based detector can be used for bio-tissue imaging based on photoacoustic detection.Finally,we point out that sandwiched graphene structures in total reflection conditions can be used in a wide range of scientific research applications,such as in the field of optoelectronic sensing,polarization modulation and so on.Furthermore,applied research can easily be extended to the analysis of optical properties and refractive index sensing of other two-dimensional materials（derivatives of graphene and other low-dimensional materials,etc.）.