Optical absorption spectroscopy of Fe2+ and Fe3+ ions in LiNbO3

We provide a method to measure concentrations of Fe2+ and Fe3+ ions in LiNbO3. The method, based only on optical absorption spectroscopy, provides a convenient means to determine the absorption cross sections for Fe2+ and Fe3+ ions, along with an independent measurement of the Fe2+ and Fe3+ concentrations in a given LiNbO3 crystal. The absorption cross section of the Fe2+ ions found by this method correlated well with a previously measured value. The cross section of the Fe3+ ions was obtained. It was also found that in some samples a significant fraction of Fe ions did not contribute to the absorption in the visible.