Fabrication And Characterization Of Mid-IR All Dielectric Metasurface

The mid infrared?mid-IR?spectrum is a strategically important band for numerical applications in realms of biomedicine,military and industry,which includes thermal imaging,sensing,free space communication and so on.Based on background of mid-IR technology,optical metasurface with advantages of high flexibility,well compatibility,easy fabrication process,has attracted great attention during last decades.Such technique utilizes light-matter interaction to realize novel optical function,which expands the design strategy of optical devices drastically and has potential to substitute the traditional fabrication recipe.Here the thesis bases on all dielectric structures and generalized Snell's law as well as Mie scattering theory to theoretically analyze and experimentally realize a Huygens metasurafce platform capable of fulfilling a diverse cross-section of optical functions in mid-IR spectrum.Besides,the thesis focuses on performance research of metasurface,while bases on nano-fabrication recipe and optical characterization method in order to figure out the application potentials,error origination as well as optimal scenario of metasurface within a series of research work.The main content of this thesis presents as follows:?1?Based on materials parameters of PbTe and CaF₂ and full-wave simulation method,the thesis designed a series of unit structures of metasurface with different geometrical parameters,which includes rectangular and H shape unit cell.With the simulation,the transmission parameters of each unit cell was obtained.According to generalized Snell's law,due to combination of these two kinds of structure mentioned above,the thesis proposed a novel design method in order to improve the work efficiency of metasurface devices under transmission mode.Such design method may pave the way for reconstruction of diffraction beam deflector and planar lenses in experiments.?2?The thesis utilized double layer lift-off recipe combined with electronic beam lithography method to fabrication diffraction beam deflector as well as planar lenses.The structure characterization revealed that the thickness of our structure was as low as₀?/8,which catered to the requirements of low profile of the devices.Furthermore,based on optical table characterization method,the metasurface devices exhibited optical efficiency up to 75%under linear polarized light condition.Compared to the state-of-the-art technique,such results presented major improvements.The image testing of planar lenses also supported the arguments that our planar lenses had diffraction-limited focusing performance.?3?The thesis utilized phase mask method in order to propose the theoretical model of Huygens metasurface.Based on this model,the thesis calculated the experimental error origination.The results revealed that the drop of experimental efficiency was ascribe to slope of the unit cells induced during fabrication procedure leading to phase shift error.Moreover,in order to further improve the optical efficiency of metasurface,the thesis proposed an optimal scenario,which could promote the theoretical efficiency by 5%.The research work in present thesis could give a guidance for development of metasurface technology.The proposed fabrication and characterization method may pave the way for the application of metasurface in future.