Simulation-Based Analysis of Thermally-Induced Stress Effects on Buried-Core Square Waveguide

Περίληψη

The objective of this study was to understand and visualize the effects of thermally-induced stresses resulting from high-temperature manufacturing processes (thermal annealing) on the performance of the buried-core square silicon waveguide. In order to do so, the photoelastic effect, which relates principle stresses and refractive indices, and its impacts were analyzed and investigated. The analysis was performed in COMSOL Multiphysics, utilizing the Finite Element Method (FEM) for numerical calculations. The equivalent stress distribution and strains in the waveguide were determined by exploiting the plane strain assumption. The anisotropic stress distribution in the waveguide caused a change in the refractive indices along the principle axes, causing a change in birefringence. Due to birefringence, optical power density distribution in different modes has experienced variations. However, in higher modes, the variation was more evident as mode splits were exhibited alongside higher optical power confinement, noting that higher confinement is advantageous for low-loss optical waveguides. Thus, it was inferred that the effect of anisotropic stresses was more substantial on higher modes rather than fundamental modes. Finally, it was evident that the mechanical properties of the cladding and manufacturing conditions could be optimized to control birefringence and subsequent performance-governing parameters.