Electro-optic, Piezoelectric and Dielectric Properties of Langasite (La3Ga5SiO14), Langanite (La3Ga5.5Nb0.5O14) and Langataite (La3Ga5.5Ta0.5O14)

Abstract

Refractive indices were determined of single crystals of La3Ga5SiO14 (langasite, LGS), La3Ga5.5Nb0.5O14 (langanite, LGN) and La3Ga5.5Ta0.5O14 (langataite, LGT) in the wavelength region between 0.36 μm and 2.33 μm. While phase-matched optical second harmonic generation is not possible in LGS it occurs in the isotypic compounds LGN and LGT. Temperature-dependent examination of the dielectric properties of LGS up to 600 °C showed anomalous behaviour. For all three substances the electro-optic [rσijk] (“unclamped”) and the piezoelectric [dijk ] tensors were determined at room temperature. In addition, the temperature-dependence of these properties was studied for LGS between –200 °C and +200 °C by a Jamin interferometer in combination with a modified Sénarmont compensator.