Design And Research On A Metasurface Made Of Titanium Dioxide Dielectric Material

Since the metamaterials were proposed and varieties of applications were achieved,there are always new research results showing the unique physical properties of metamaterials,and stimulating the enthusiasm in exploring the field of artificial electromagnetic metamaterials in the few decades.With the ever-changing technology today,only the metasurfaces which inherited the unique physical properties of metamaterials can meet the raising requirements for the miniaturization and planarization of the devices.In the meantime,the metallic material is limitted in applications of electromagnetic devices due to the ohmic loss.Hence the all-dielectric metasurface working under Mie scattering theory has received more and more attention.Among all these dielectric materials,titanium dioxide stands out for its excellent optical properties,making it possible to fabricate metasurface devices which works in the visible light.In this paper,a metasurface based on titanium dioxide dielectric antenna is designed.After confirming the function of light manipulation,the applications of titanium dioxide metasurface in meta-lens and meta-hologram are finally realized.Aiming at the electromagnetic control of the visible light,this paper proposed an idea of using titania antenna as a structure unit of metasurface.As titanium dioxide antenna is an important medium to realize the full control of wavefront,it's required to study the titania antenna so as to accomplish the metasurfaces with special functions.This paper established the unit cell model of titanium dioxide.Under the premise of determining the key geometric parameters and optical parameters in the model,the relationship between the size change in titania antenna and the wavefront control was studied,which established a solid foundation for the design of metasurfaces with specific functions.The anomalous reflection or refraction is a common phenomenon caused by metasurface.After obtaining the relationships between the titania antenna and the phase,amplitude and polarization of the reflected light,the method which can easily testify the validity is to design the abnormal titanium dioxide metasurface.In this paper,anomalously reflective metasurface based on titanium dioxide was designed,and the samples were fabricated by using the simple and feasible micro-nano processing method,such as electron beam evaporation and electron beam lithography.Anomalous reflection phenomenon was observed through the optical system,and the sample reached a relatively high efficiency of 49.17 %.The realization of the anomalous reflection phenomenon further confirms the light manipulation ability of the titania antenna,and more interesting structures can be designed.In this paper,a metasurface wich can focus the light was designed according to the equation of the phase distribution of the focus lens and the beam focusing ability of the metasurface was experimentally verified.This paper has also designed a metasurface with holographic projection phenomenon.The holograms of English abbreviation and school badge of Harbin Institute of Technology were realized by these metasurfaces.And the work wavelength of the metasurface was expanded from 632 nm to 520 nm and 445 nm,which almost cover the whole visible light spectrum.The calculated hologram conversion efficiency in red light reached 36.7 %.