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The electro-optic (EO) coefficients r 22 of a congruent LiTaO 3 bulk crystal, with dimensions of 6 × 5 × 20 mm 3 ,havebeen measured over a wide frequency range (from dc up to 150 MHz) using the novel and elaborate step-voltage time-response method (TRM). At low frequencies, these results are compared with those obtained with the frequency-doubling EO-modulation (FDEOM) method. From these measurements, the clamped and unclamped EO coefficients, r S ,respectively, have been derived and the acoustic contribution r a 22 to the EO effect has been deduced and compared with theoretically calculated values. Also, using the values of acoustic contribution, r a ,thetrue value of the EO coefficient r 22 has been extracted. Lastly, the above results are compared with those obtained for a pure congruent LiNbO 3 crystal in the framework of a typical intensity-modulation (IM) EO system.

In spite of the large utilization of LiNb0 3 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 LiNb0 3 has been determined by an accurate technique issued from the Senarmont methodo At room temperature, Y c = 19.9 X 10-12 m/V, with an estimated error of ± 5%. The measurements are performed for values of the de 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 accounto

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A novel system is presented which is capable of measuring with high accuracy the linear (Pockels) electro-optic effect by means of a new dynamic (ac) method. This method is based on the observation of the photodetected output obtained from a Senarmont-type ellipsometric system with an ac (modulating) voltage being applied onto the electro-optic sample under test. This observation is made on a high sensitivity oscilloscope and allows us to determine accurately the null point of the system by locating the position of the analyzer that produces in the output a characteristic and abrupt doubling of the (modulation) frequency. By locating this frequency doubling position without and with electric field one can finally determine the corresponding electro-optic coefficients. Theoretical analysis and considerations of practical interest are presented in the article and show that the system in question can ensure reduced errors and increased sensitivity. Also, experimental evidence in support of the expected performance is obtained by implementing and applying the system for the measurement of the composite electro-optic coefficient rc of LiNbO3 for various temperatures in the range of 17–20 °C.