Induced-dipole-electric-field contribution of atomic chains and atomic planes to the refractive index and birefringence of nanoscale crystalline dielectrics

The induced-dipole-electric-field contribution to the refractive index at any location within a nanometerscale dielectric is quantified by summing the electronic dipole contributions due to all the surrounding atoms in the dielectric. Using a tetragonal lattice and varying the ratio of lattice constants illustrates the important limiting chainlike and planelike behaviors. Strong polarizing effects and thus high refractive indices occur for an electric field applied along the length of a chain of atoms or applied in a planar direction to a plane of atoms. In contrast, a strong depolarizing effect and thus low refractive indices occur for an electric field applied normal to a chain of atoms or applied normal to a plane of atoms. Birefringence is increased or decreased by the simultaneous presence or absence of polarizing and depolarizing effects.