Kerr Type Electro - Optic Effect in Solid Dielectrics

Electrically induced optical birefringence having a second power field dependence (Kerr effect) has been identified in common amorphous, transparent, dielectric materials such as PMMA, polyethylene, and cross-linked polyethylene. Using a He-Ne laser the relative phase retardation of light passing through an electrically stressed sample placed between crossed polarizers has been measured. An electrooptical coefficient of less than 0.1% of the Kerr coefficient in nitrobenzene has beenter-determined for PMMA samples. Even smaller values have been measured for PE samples. The measurements in PE are made for a range of temperatures in which the materials are transparent to visible light.ntri-Contributions from Maxwell stress towards the total observed effect have been determined independently. The measurement of substantial Kerr-type effect in PE is particularly significant as it makes possible a non-destructive technique of mapping electric fields around voids and inclusions within such polymeric insulation.