First-principles study of vibrational and dielectric properties of {\beta}-Si3N4

First-principles calculations have been conducted to study the structural, vibrational and dielectric properties of {\beta}-Si3N4. Calculations of the zone-center optical-mode frequencies (including LO-TO splittings), Born effective charge tensors for each atom, dielectric constants, using density functional perturbation theory, are reported. The fully relaxed structural parameters are found to be in good agreement with experimental data. All optic modes are identified and agreement of theory with experiment is excellent. The static dielectric tensor is decomposed into contributions arising from individual infrared-active phonon modes. It is found that high-frequency modes mainly contribute to the lattice dielectric constant.Comment: 15pages, 1 figure, 5 table

Coherent model for cross-polarization coupling from a single point-like perturbation in optical fibers

The transfer matrix is proposed to describe the coherent cross-polarization coupling (CPC) induced by a single point-like perturbation (PLP) in optical fibers. This matrix remains independent of the fiber length, making it suitable for characterizing the PLP that have a zero-dimensional impact on fiber length. Consequently, the fiber can be fully characterized by a matrix combining the transfer matrix of CPC and the Jones matrix of the fiber birefringence. The polarization performance of fibers exhibiting both CPC and birefringence is analyzed using the developed combined model