Influence of the temperature-dependent spontaneous birefringence in the electro-optic measurements of LiNbO3

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Abstract
In spite of the large utilization of LiNbO3 in optical devices, its electro‐optic coefficients are not perfectly known. We show in the present paper that not taking into account the temperature dependence of the linear spontaneous birefringence can lead to an erroneous determination of the electro‐optic coefficients. The electro‐optic coefficient rc of LiNbO3 has been determined by an accurate technique issued from the Sénarmont method. At room temperature, rc=19.9×10−12 m/V, with an estimated error of ±5%. The measurements are performed for values of the dc applied electric field as a function of the temperature around room temperature. We point out the drastic influence on the electro‐optic response of the spontaneous birefringence variation due to the temperature. Accurate and reproducible values of the electro‐optic coefficients are obtained only if this dependence is taken into account.