Refractive indices of lithium niobate as a function of wavelength and composition

Abstract

An interferometric method is applied to determine the refractive indices of lithium niobate single crystals over a wide wavelength and composition range. A generalized two term Sellmeier equation is proposed that describes the refractive indices as a function of wavelength and stoichiometry. On the basis of this generalized Sellmeier equation the parameters of nearly all optical characterization methods for LiNbO3 can be calculated. By means of a Kramers-Kronig analysis the shift in the UV absorption edge and the change in the extraordinary refractive index with the composition can be referred to each other. Excellent agreement is found with the respective experimental values.