Temperature dependence of the absorption and refraction of Mg-doped congruent and stoichiometric LiNbO3 in the THz range

The absorption coefficient and the index of refraction of undoped and Mg-doped stoichiometric and congruent LiNbO3 crystals were determined for polarization parallel to the z axis in the far-infrared (FIR) 30−180-cm−1 frequency range for different Mg-doping levels and temperatures down to 10 K. For stoichiometric LiNbO3, smaller absorption and index of refraction were found, than for congruent samples. At a Mg content near the photorefractive threshold, the FIR absorption coefficient has the lowest value in the stoichiometric crystals, which are most suitable for efficient pulse generation in the terahertz range.