This paper presents computations of the electric polarizability of a uniform isotropic dielectric parallelepiped, obtained by an application of the Moment Method, over a range of relative permittivities from 5 to 100, and relative dimensions from lxlxl to lxlxl4 and from lx2xl to lx2x14, where the electric field is applied along the major axis. The results are useful in quantifying the sensitivity of and far-field scattering by an electrically small electric-field probe employing direct field coupling to an electro-optic crystal. For example, a crystal with dimensions 1 mmxl mmx10 mm and a relative permittivity of 50 has a computed polarizability of 195.mm3 along the major axis, which corresponds to an average internal electric field intensity of .398 times the applied field intensity.
Michael A. Gilbert,
"Polarizability Of An Electro-Optic Parallelepiped Crystal", Proc. SPIE 0720, High Bandwidth Analog Applications of Photonics, (11 March 1987); doi: 10.1117/12.937617; https://doi.org/10.1117/12.937617