Design Optimization of Polarization Insensitive Polymer Optical Waveguide Devices Considering Stress-Induced Effects.

As optical communication networks continue to expand into residential and commercial settings, there has been a growing interest in polymer-based optical waveguide devices, because they are relatively easy to fabricate and permit mass production at lower costs. Polymer waveguides also have the potential to achieve low power consumption compared with conventional silica-based devices. However, alongside these benefits, a critical design challenge has emerged: polarization dependence. The polarization-insensitive operations are particularly essential for applications in optical fiber communications, as they can greatly reduce the complexity of a system. One of the primary contributors to polarization dependence is the internal stress generated during the waveguide fabrication process. This unavoidable stress alters the material's refractive index through the stress-optic effect, leading to anisotropy or birefringence in the waveguide. While it is theoretically feasible to achieve polarization-insensitive behavior by carefully designing the waveguide geometry, neglecting stress-induced birefringence can make this process highly complex and inefficient. Therefore, accurately predicting the stress distribution within the waveguide structure and understanding its impact is crucial for the effective design of integrated optical devices. This study undertakes a comprehensive study of stress-induced birefringence in polymer-based optical waveguides. It explores the origins and implications of stress-related effects and proposes design strategies of some basic polarization-insensitive waveguide devices in relation to stress-induced effects, thereby addressing a critical challenge in the development of next-generation optical communication technologies.