Preparation And Optical Properties Of Tantalum Niobium Based High Refractive Index Films

With the development of integrated optics and laser technology,the demand for high refractive index optoelectronic functional materials,especially high refractive index thin-films,is becoming more and more urgent.Tantalum-niobium based optical film,a promising optical material,has high refractive index and low optical absorption in the range of visible light.In this paper,based on the relevant theories and experiments,the electrical and optical properties of the tantalite-niobate bulk and film materials have been calculated,and high-quality tantalite-niobate optical thin-films were fabricated,the structure and basic optical properties of tantalite-niobate optical thin-films were investigated.Furthermore,the third-order nonlinear optical properties of thin-films were studied.The model of tantalum-niobium based bulk and thin-film materials were established,the calculation of its structure and optical properties indicates that the valence band of tantalum-niobium thin-films is mainly contributed by the p orbit of oxygen ions and d orbits of partial B cations,while the conduction band is primarily contributed by the d orbit of cations and the p orbit of partial oxygen ions.In the range of visible light,the refractive index decreases with the increase of the wavelength,this belongs to the normal dispersion.At the same incident wavelength,the refractive index of the Nb₂O₅ films is greater than that of the Ta₂O₅ films,and the spectra,such as dielectric function and reflectivity,have different degrees of red shift compared with that of Ta2O5 films.Tantalum-niobium based targets were prepared by using of electric spark sintering?SPS?,and the optical films have been successfully fabricated on Pt?111?/Ti/SiO₂/Si,single crystal Si and fused silica glass substrates by using Pulsed Laser Deposition?PLD?.Its micromorphology test characterized that the surface of films is smooth without crack.The optical properties of thin-films were measured by using ultraviolet-visible photometer and ellipsometer,and the thickness parameter and optical band gap of films were studied based on the properties of transmission and absorption.In the range of visible light,the transmittance of thin-films reaches70⁹0%.The trend of the refractive index spectral lines on different substrates is the same,showing normal dispersion.At the same wavelength,the refractive index of Nb₂O₅ film is greater than that of Ta₂O₅ film,which is consistent with the result of theoretical calculation.The refractive index spectra conform to the Cauchy model,the parameters of the refractive index equation of thin-films on different substrates were obtained.The incorporation of La elements can regulate the refractive index of the Nb₂O₅ film,the refractive index between Ta₂O₅ and Nb₂O₅ films was accurately regulated by adding La elements with different concentrations,obtaining the rate of regulation of the refractive index on different substrates.Moreover,the third-order nonlinear optical properties of tantalum-niobium based films were studied by using Z-scan,its transmittance normalized curve appears peak valley characteristics,and the nonlinear refractive index coefficient n₂'<0 shows that it has self-defocusing phenomenon.Finally,it is calculated that the nonlinear refractive index coefficient of Nb₂O₅ film is-2.33×10^-9cm²/W,which is larger than-1.42×10^-9cm²/W of Ta₂O₅ film.