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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 11: Dielectric, Elastic and Electromechanical Properties
KFM 11.1: Vortrag
Dienstag, 13. März 2018, 10:00–10:20, EMH 025
Optical properties of titanium-doped lithium niobate from time-dependent density-functional theory — •Michael Friedrich1, W. G. Schmidt1, Arno Schindlmayr1, and Simone Sanna2 — 1Department Physik, Universität Paderborn, 33095 Paderborn, Germany — 2Institut für Theoretische Physik, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen
Lithium niobate (LiNbO3) is a dielectric crystal with outstanding electro-optical properties that is widely used for optical waveguides and other commercial applications. The usage in waveguides is made possible by titanium indiffusion. Although this technique has been used for decades, the underlying microscopic processes during indiffusion and the definite lattice sites that are occupied by titanium are insufficiently known to this day.
We model the properties of pristine and titanium-doped LiNbO3 from first principles. The dielectric functions are calculated within time-dependent density-functional theory, and a model long-range contribution is employed for the exchange-correlation kernel in order to account for the electron-hole binding. Our study focuses mainly on the influence of substitutional titanium atoms on lithium sites. We show that an increasing titanium concentration enhances the values of the refractive indices and the reflectivity [1]. This effect cannot be observed by titanium atoms occupying niobium sites.
[1] M. Friedrich et al., Phys. Rev. Materials 1, 034401 (2017).