Refractive indices in undoped and MgO-doped near-stoichiometric LiTaO3 crystals

Undoped and MgO (0.5 and 1.0-mol%)-doped near-stoichiometric LiTaO3 (SLT) crystals were grown from off-congruent Li-rich solutions (Li similar to 60 mol%) by the double-crucible Czochralski method using a continuous SLT ceramic grain charging system. Curie temperatures of the undoped and MgO (0.5 and 1.0-mol%)-doped SLT crystals are 688, 694 and 695degreesC, respectively. The ordinary and extraordinary refractive indices (n(o), n(e)) of these crystals were measured by the prism coupling technique in the wavelength range from 0.440 to 1.050 mum at room temperature, and the temperature-independent Selimeier equations for each crystal were derived from the measured refractive index data, n(o) of the SLT crystal was almost the same as that of a congruent-melt LiTaO3 (CLT) crystal, while n(c) of the SLT crystal was lower than that of the CLT crystal. n(e) was lower than n(o) for the SLT crystal, similar to as in the case of the LiNbO3 crystal. The refractive indices of the SLT crystal, n(o) and n(e), were found to be almost independent of MgO concentration at the doping level of 0.5 and 1.0 mol%.