Pyroelectric and Optical Properties of Potassium Lithium Niobate

Abstract

The measurements were made on the dielectric constant, refractive index, electro-optic coefficient and spontaneous polarization of the crystals (K2O)0.30(Li2O)0.70-x(Nb2O5)x with x=0.53∼0.55. The spontaneous polarization was experimentally determined by the pyroelectric current method. The pyroelectric current was superposed by an anomalous absorption current above 200°C, which could be reduced by deep polishing of the crystal surface after the poling, or discriminated from the former by the observation of the time change of the current. An ordinary temperature dependence of the spontaneous polarization was observed, and the result gave no evidence of a positive temperature gradient of Ps near the room temperature reported before. The birefringences were explained by the quadratic Kerr effect biased by the spontaneous polarization, and the quadratic electro-optic coefficient gc=0.09 m4/C2 was obtained. With this gc value the linear electro-optic effect could not be explained except in the vicinity of the Curie temperature.