Determination of homogeneity of pure and doped lithium niobate by second harmonic generation temperature phase matching

Employing a comprehensive Sellmeier equation for the refractive indices, we derive calibration curves to be used for the homogeneity characterization of lithium niobate. Applying the calculated results, quantitative homogeneity parameters can be derived from temperature tuning curves for noncritical second harmonic generation, which are usually measured to state the composition of the material. The calibration method is of interest and presently is being used for pure as well as Mg-, Zn-, and In-doped crystals in the whole concentration regime.