Concentration Determination of Er3+ in LiNbO3 Crystal by Absorption Spectroscopy

Abstract

A number of X-, Y-, and Z-cut congruent or near-stoichiometric only Er3+-doped or Er3+/Dn+-codoped (Dn+=Mg2+, Zn2+, In3+, Yb3+) LiNbO3 crystals were grown by the Czochralski method. The Er3+ concentrations in these crystals were determined at first from neutron activation analysis. Then, the integrated unpolarized Er3+ absorption coefficient at the 1.5 μm wavelength region was measured as a function of Er3+ concentration in crystal. The results show that the integrated absorption coefficient (IAC) is linearly proportional to the Er3+ concentration in the crystal ([Er3+]crystal) whether the crystal is only Er3+-doped or Er3+/Dn+-codoped, and the fitted expression is IAC=(95.0±4.6)·[Er3+]crystal for the X- or Y-cut crystals and IAC=(102.0±5.1)·[Er3+]crystal for the Z-cut ones. These linear expressions enable to establish an optical method used to accurately determine Er3+ concentration in any only Er3+-doped or Er3+/Dn+-codoped LiNbO3 crystal from the simple and rapid unpolarized absorption measurement, and the error is within 10%.