The Design And Preparation Of Titanium Dioxid Based Metasurface

Metasurface,a novel type of two-dimensional metamaterial,has gained increasing attention due to the unique abilities in light manipulation.In contrast to the phase changes via propagations in conventional systems,metasurface can introduce abrupt changes on both phase and amplitudes of waves via arrays of optical resonators.In this sense,the dependence of propagation effects can be simply released and thus a number of novel t wo-dimensional devices have been proposed and experimentally demonstrated in past few years,e.g.anomalous reflection/refraction,surface-wave coupling,high-resolution optical hologram and so on.The initial metasurfaces are designed and realized in arra ys of metallic resonators.But the huge intrinsic losses of metal have strongly limited the converting efficiency,especially in near-infrared and visible wavelength range.To improve the reflection coefficient,all-dielectric metasurfaces have been proposed and fabricated by replacing plasmonic resonances with Mie scattering resonances.Because of the high refractive index and wide band gap?anatase 3.2 e V and rutile 3.0 e V?,titanium dioxide?TiO₂?has been considered as an alternative materials for all-dielectric metasurfaces in visible range.The main works in this thesis is shown as below:In this paper,we deposited TiO₂ films by electron beam evaporation,and studied the effects of the film composition,surface morphology and micro structure with different annealing conditions.The experimental results showed that the optimal annealing temperature can improve the crystalline grain and the TiO₂ film has obvious?101?preferred orientation.Therefore,the refractive index of TiO₂ thin films can be optimized by optimizing the annealing temperature.The thickness,refractive index and extinction coefficient of the thin film are measured by ellipsometry,and the annealing process of the film refractive index is determined.The process of TiO₂ thin film with excellent structure and optical properties by electron beam evaporation was studied.After the TiO₂ film with high refractive index is realized,we proposed an abnormal reflection type super surface structure based on Ti O 2 rectangular array.It is found that the phase delay of 0-2p can be achieved by controlling the array period,the thickness of the spacer layer and the size of the rectangular element.In this paper,the rectangular array is arranged according to the phase delay gradient,and the working wave band is designed and simulated in the 632 nm.When the design of the abnormal mirror is completed,we studied the preparation process and the primary technology of the super surface device.Device was prepared by electron beam etching and plasma etching,and the etching rate of TiO₂ thin film was determined.The experimental results show that the micro nano structure can be prepared by optimizing the electron beam focusing energy and other processes.In this paper,the preparation technolog y of titanium dioxide thin film which has the characteristics of high density,high dielectric loss and low loss,is the basis for the preparation of the abnormal mirror.The medium type and design and devices in the super surface in the near infrared and visible wavele ngth range with a small loss,simple structure,high reflectivity.It makes the research and application of super surface device has a constructive significance.