A mathematical model to study the phase difference introduced between the two orthogonal components of light wave
due to electro-optic effect in a trapezoidal shaped lithium niobate single crystal has been made. Here, the electrodes are
placed on the two opposite non-parallel faces such that the field is nearly perpendicular to the light beam direction. It is
found that for the said geometry of the device structure, the maximum phase difference is a function of oblique angle
between the two non-parallel faces, which has a critical value. Using random optimization technique based on genetic
algorithm, the device parameters can be optimized for any required phase change between the two components of light
wave. The phase difference between the two orthogonal components of light can be made tunable by using a multi-strip
electrode structure. The advantage of this technique is that tunability can be obtained with a constant voltage source.
A simple interferometric technique for measurement of the internal field (IF) in a ferroelectric crystal has been proposed. This technique has several advantages over the other methods used previously for evaluation of IFs in ferroelectric crystals. Here, the electro-optic property of lithium niobate is exploited for quantitative analysis of its IF. The strength of IF obtained using this technique lies within the range given in the literature. However, at frustrated domain inversion state, the measured value of IF shows a reduced value. A possible reason for this reduction based on the defect model has been discussed.