Structure And Optical Properties Study Of Lithium Niobate Crystals Single Doped With Hafnium Or Zinc Based On First Principle Method

Due to its characteristics of large storage capacity, parallel writing and reading andfast access, the optical volume holographic storage becomes the most popular storagemode today. The key element that influences the holographic storage is the quality ofstorage media. LiNbO₃crystals, with its characteristics of stable performance, easy growth,low cost and easy doping, turn into the most studied of the volume holographic storagematerial. But the “optical damage” effect appeared in application affect its use seriously inthe holographic storage. In this article, from the side of theoretical calculations, viadensity functional theory based on first-principles, calculates the electronic structure andoptical properties of LiNbO₃crystals, Zn:LiNbO₃crystals and Hf:LiNbO₃crystals, anddiscusses the influence that the microscopic structural changes have on the macro opticalproperties of the crystals.Firstly, Materials Studio was used to build3D models of LiNbO₃crystals, geometryoptimization for the models was conducted, the properties, such as band structure, densityof states, sub-state density of LiNbO₃crystals were calculated and the results wereanalysed. Then, the dielectric function, absorption spectra, reflection spectra, which arerelated to the optical properties of LiNbO₃crystals, were calculated, obtaining anddiscussing the relationship between the microstructure and basic optical properties ofLiNbO₃crystal.Secondly, with Zn-doped LiNbO₃crystals, in which Zn is the traditional opticaldamage resistance element, as the object of study and the experimental data as the basis,the calculation model of Zn:LiNbO₃crystals was built. Because of the new extrinsicdefects that Zn causes in Zn:LiNbO₃crystals, the geometry optimization for Zn:LiNbO₃crystals were conducted. Based on the geometry optimization, the electronic structure ofZn:LiNbO₃crystals, compared to that of LiNbO₃crystals, was calculated, and the changesof electronic structure of LiNbO₃crystals that caused by doping Zn was analysed.Then theoptical properties of Zn:LiNbO₃crystals were calculated and compared with that ofLiNbO₃crystals. Finally, with Hf-doped LiNbO₃crystals, in which Hf is the new optical damageresistance elements, as the object of study, the electronic structure and optical properties ofHf:LiNbO₃were calculated. For charge balance, three Li vacancies form around Hf ion,thus larger calcultion models were built compared to LiNbO₃crystals and Zn:LiNbO₃, thegeometry optimization was also conducted. After the geometry optimization, theelectronic structure and optical properties of Hf:LiNbO₃crystals were calculated again,and the results were compared to LiNbO₃crystals and Zn:LiNbO₃crystals. Then thereasons for the changes of electronic structure and optical properties of LiNbO₃crystalscaused by doping Hf were discussed.