KERR ELECTROOPTIC THEORY AND MEASUREMENTS OF ELECTRIC-FIELDS WITH MAGNITUDE AND DIRECTION VARYING ALONG THE LIGHT PATH

Differential equations that govern light propagation in Ken media are derived when the applied electric field direction and magnitude vary a long the light path. Case studies predict Ken electro-optic fringe pat terns for the specific case of point/plane electrodes. We apply the ch aracteristic directions theory of photoelasticity to understand these fringes. We also study birefringent media with small Ken constant, in particular transformer oil. For this case we show that simplications i n the characteristic parameter theory is possible, resulting in simple integral relationships between the characteristic parameters and the applied electric field. We use these simple relationships to extend th e ac modulation method to measure the characteristic parameters for sm all Ken constant media. Measurements of the characteristic parameters using the ac modulation method are presented for point/plane electrode s in transformer oil. The measurements agree reasonably well with spac e charge free theory for infinite extent electrodes for which analytic al expressions are available. We finally employ the 'onion peeling' me thod to reconstruct the axisymmetric electric field magnitude and dire ction from the measured characteristic parameters and compare the resu lts to the analytically obtained electric field.