The optical response of thin dielectric films can be influenced by grain morphology and the presence and distribution of defects. In the limit of random defects and small electric field amplitudes, approximate methods exist to model the real part of the dielectric constant in terms of volume fractions and bulk dielectric constants of the film components. Explicit inclusion of nonlinear polarizabilities and details of the microstructure, such as particle phase, shape, and orientation requires a more exact approach.
We have developed a method to self-consistently determine the local internal electric field and polarization in the long wavelength limit for model films with a random distributions of defects of arbitrary phase and orientation. From this we have calculated the real part of the dielectric constant as a function of nonlinear polarizability of the components, and have shown the effect of defect phase and orientation on the dielectric constant of the film.